Category Archives: Chemistry

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Crystalline Structure

A.      Primitive Cubic Unit Cells

  • Polonium crystallizes in a primitive cubic unit cell. The side of a unit cell is measured through X-ray diffraction to be 3.80 Å. What is the radius of a polonium atom in Å?

we know that in primitive cubic unit cell side = 2r

so

3.8 = 2r

R = 1.9

so

the radius of a polonium atom is 1.9 Ao

  • What is the volume, cm3 of a single polonium atom?(Assume that atoms are spherical. Do you remember what the formula for the volume of a sphere is?)

Volume of sphere = (4/3) x pi x r3

so

Volume of single polonium atom = (4/3) x pi x (1.9 x 10-8)^3

Volume of single polonium atom = 2.871634 x 10-23 cm3

  1. What is the total volume, cm3 of polonium atoms inside the unit cell?

Only one atom in unit cell

so

Total volume of polonium atoms inside the unit cell

= 2.871634 x 10^-23cm3

  • What is the volume of a unit cell of polonium, cm3?(Do you remember the formula for the volume of a cube?)

Volume of unit cell = a3

Volume of unit cell = ( 3.8 x 10-8)^3

Volume of unit cell = 5.4872 x 10-23 cm3

  1. What is the percent of occupied volume in a unit cell of polonium?

% volume occupied = volume of polonium atom / volume of unit cell

% volume occupited = 2.871634 x 10-23 x 100 / 5.4872 x 10-23

% volume occupied = 52.33

  1. What is the mass, g of a unit cell of polonium?

Molar mass of polonium = 209 g /mol

so

Mass of one atom = molar mass / avagadro number

Mass of one atom = 209 / (6.022 x 10^23)

Mass of one atom = 3.4706 x 10-22 g

as

One unit cell contains one polonium atom

Mass of unit cell = 3.4706 x 10-22 g

  1. What is the density, g/cm3 of a sample of polonium?

Density = mass of unit cell / volume

Density = 3.4706 x 10-22 / (5.4872 x 10-23)

Density = 6.325 g/cm3

  1. What is the coordination number of an element that arranges in a primitive cubic unit cell?

The coordination number of simple cubic unit cell is 6

B.      Face-Centered Cubic Unit Cells

  • Aluminum crystallizes in a face-centered cubic unit cell. The density of aluminum is 4.05 g/cm3. What is the mass, g of aluminum in the unit cell?

gram sper atom Aluminum

= 26.98 g mol^-1/ 6.022x 10^23 atomsmol^-1

=4.480×10^23 g/atoms

  1. What is the volume, cm3 of the unit cell in cubic centimeters?

density= mass/ volum

Volum=(1.792×10^-22 g/unit cell)/ 4.05 cm^-3

= 4.42469 x 10^-23 cm^3 per unit cell

  1. What is the side of the unit cell in centimeters.

Density= Mass x no of atom / a^3 x Na

4.05= (26.99 x 4)/a^3 x 6.023 x 10^23

a^3= (26.99 x 4)/ 4.05 x 6.023 x 10^-23

a= 7.62 x 10^-7

  1. What is the radius of aluminum in angstroms?

a = 2π √2

7.62 x 10^-7 = 2x π x 1.414

π= 2.7 x 10 ^-7 cm

  1. What is the total volume, cm3 of aluminum atoms inside the unit cell?

Volume = a^3

= 4.426 x 10 ^ -23 cm^3

  1. What is the percent of occupied volume in a unit cell of aluminum?

No of atom = 4

pakage factor =(No. of atoms) (vol. of each atom) / (vol. of unit cell)

P.factor= 0.74

74% is occupied by atom and 26% is empty

  1. What is the coordination number of an element that arranges in a face-centered cubic unit cell?

The coordination number of face center cubic unit cell is 12

C.      Body-Centered Cubic Unit Cells

  1. An element crystallizes in a body-centered cubic unit cell. The radius of this element is found to be is 2.20Å. The density is 0.991 g/cm3. What is the side of the unit cell in centimeters?

Radius (r) = 2.20 A

4 r = 4.80 A

d^2= (√20)^2 = (4r)^2

d^2= (d √2)^2= (4.80)^2

3d^2 = 23.04

d^2= 23.04/3

d = (√23.09/3) = 3.39 A

3.39×10^-10m = 3.39x 10 ^-8cm

  1. What is the volume, cm3of the unit cell?

Volume = d^3

= 3.894x 10^-23 cm^3

  1. How many moles of atoms are within one unit cell?

atom per unit= 2

  1. What is the molar mass of this element?

= (0.991/1cm^3) x 3.899x 10 ^-23 cm^3 = 3.86×10^-23 g

2 atoms contain one unit cell

= 3.86 x 10 ^-23g/2 mol = 1.93x 10 ^-23g

Molar mass= 1.93x 10 ^-23 x 6.022x 10 ^-23

= 11.6

  1. Which element do you think that this is? C
  1. What is the total volume, cm3 of this element inside the unit cell?

R= 202x 10 ^-8cm

Total volum occupied by atom= 4 x 2 x 3.14 x (2.2 x 10^-8 cm)^3= 89.176 x 10 ^-24 cm^3

  1. What is the percent of occupied volume in a unit cell of this element?

edge length = 4.R/1.73= 5.08x 10^-8 cm

Volum of cube= (5.08 x 10 ^-8 cm)^3 = 131.1 x 10^-24 cm^3

Percentage occupied = 89.176 x 10^-24 cm ^-3 x 100/131.1x 10^-24 cm^3

= 68.02%

  1. What is the coordination number of an element that arranges in a body-centered cubic unit cell?

Coordination number = 8

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Help-General Chemistry


Help-General Chemistry II (CHE-112)

Section no.:

Semester and year:

 

 

Written Assignment 6: Reactions of Acids and Bases

 

Answer all assigned questions and problems, and show all work.

 

  1. Determine the pH of (a) a 0.40 M CH3CO2H solution, (b) a solution that is 0.40 M CH3CO2H and 0.20 M NaCH3CO2. (8 points)

 

(Reference: Chang 16.5)

 

 

 

 

 

  1. Which of the following solutions can act as a buffer? (a) KCl/HCl, (b) KHSO4/H2SO4, (c) KNO2/HNO2. (5 points)

 

(Reference: Chang 16.9)

 

 

 

 

  1. Calculate the pH of the buffer system made up of 0.15 M NH3/0.35 M NH4 (5 points)

 

(Reference: Chang 16.11)

 

 

 

 

  1. The pH of a bicarbonate-carbonic acid buffer is 8.00. Calculate the ratio of the concentration of carbonic acid (H2CO3) to that of the bicarbonate ion (HCO3). (5 points)

 

(Reference: Chang 16.13)

 

 

 

 

 

  1. The pH of a sodium acetate–acetic acid buffer is 4.50. Calculate the ratio [CH3COO]/[CH3COOH]. (5 points)

 

(Reference: Chang 16.15)

 

 

 

 

 

  1. Calculate the pH of the 0.20 M NH3/0.20 M NH4Cl buffer. What is the pH of the buffer after the addition of 10.0 mL of 0.10 M HCl to 65.0 mL of the buffer? (8 points)

(Reference: Chang 16.17)

 

 

 

 

 

 

  1. A 0.2688 g sample of a monoprotic acid neutralized 16.4 mL of 0.08133 M KOH solution. Calculate the molar mass of the acid. (5 points)

 

(Reference: Chang 16.27)

 

 

 

 

 

 

  1. In a titration experiment, 12.5 mL of 0.500 M H2SO4 neutralize 50.0 mL of NaOH. What is the concentration of the NaOH solution? (5 points)

 

(Reference: Chang 16.29)

 

 

 

 

 

 

  1. A 0.1276 g sample of an unknown monoprotic acid was dissolved in 25.0 mL of water and titrated with 0.0633 M NaOH solution. The volume of base required to bring the solution to the equivalence point was 18.4 mL. (a) Calculate the molar mass of the acid. (b) After 10.0 mL of base had been added during the titration, the pH was determined to be 5.87. What is the Ka of the unknown acid? (10 points)

 

(Reference: Chang 16.31)

           

 

 

 

  1. Calculate the pH at the equivalence point for the following titration: 0.20 M HCl versus 0.20 M methylamine (CH3NH3; Kb = 4.4 × 10–4) (5 points)

           

(Reference: Chang 16.33)

 

 

 

 

  1. A 25.0 mL solution of 0.100 M CH3COOH is titrated with a 0.200 M KOH solution. Calculate the pH after the following additions of the KOH solution: (a) 0.0 mL, (b) 5.0 mL, (c) 10.0 mL, (d) 12.5 mL, (e) 15.0 mL. (25 points)

 

(Reference: Chang 16.35)

 

 

 

 

  1. Referring to the following table:

 

Indicator Color in Acid Color in Base pH Range*
Thymol blue Red Yellow 1.2–2.8
Bromophenol blue Yellow Bluish purple 3.0–4.6
Methyl orange Orange Yellow 3.1–4.4
Methyl red Red Yellow 4.2–6.3
Chlorophenol blue Yellow Red 4.8–6.4
Bromothymol blue Yellow Blue 6.0–7.6
Cresol red Yellow Red 7.2–8.8
Phenolphthalein Colorless Reddish pink 8.3–10.0

*The pH range is defined as the range over which the indicator changes from the acid color to the base color.

 

Specify which indicator or indicators you would use for the following titrations:  (9 points)

  1. HCOOH versus NaOH
  2. HCl versus KOH
  3. HNO3 versus CH3NH2

 

(Reference: Chang 16.43)

 

 

 

 

 

  1. The pKa of butyric acid (HBut) is 4.7. Calculate Kb for the butyrate ion (But). (5 points)

 

(Reference: Chang 16.97)

 

 

 

 

 

EXPERIMENT 25 MOLECULAR FLUORIMETRY, AND THE ANALYSIS OF POLYCYCLIC AROMATIC HYDROCARBONS (PAHs) IN CIGARETTE SMOKE


EXPERIMENT 25
MOLECULAR FLUORIMETRY, AND THE ANALYSIS OF  POLYCYCLIC AROMATIC HYDROCARBONS (PAHs) IN CIGARETTE SMOKE
INTRODUCTION Following the initial absorption of radiation, a molecule may de-excite in a variety of ways, one of which is the fluorescent re-emission of a photon. As a spectroscopic technique, fluorescence has the advantage over absorption in that it has a greater sensitivity.
One class of molecules in which fluorescence is the dominant relaxation mechanism is the polycyclic aromatic hydrocarbons (PAH). These are of special interest not only because many of them are confirmed carcinogens, but also because they are quite commonly formed (in minute quantities) in the combustion of cellulosic materials.  PAHs are discharged into our environment as the by- products of the combustion of fossil fuels.  Other sources of PAHs include industrial processes, biomass burning, waste incineration, oil spills and cigarette smoke. While low molecular weight PAHs are gases, most PAHs have low vapour pressures and hence are adsorbed on airborne particles. These organic compounds have also been found in aquatic environments. The Environmental Protection Agency (EPA) has identified 16 PAHs as priority pollutants. Therefore, understanding the properties of PAHs, particularly as related to their qualitative and quantitative analysis, is important and highly relevant.  It is thus not surprising that a substantial effort has gone into developing a sensitive analytical technique for their detection, nor (from what has been said above) that the method-of-choice should be fluorimetry.
AIM This experiment quantitatively determines the relative PAH concentration in low, medium and high tar cigarettes and examines the efficiency of the cigarette filter using fluorescence spectroscopy.
gln/jun2000/jul2001cfh/Mar2007, ed/er/May2008 2.
THEORY General Aspects Reference [1] describes the basic spectroscopic principles, while [2] outlines examples of analytical applications. An adequate introduction to the theoretical aspect of molecular fluorescence  and a detailed account of the molecular-structural factors relevant to the fluorescence of organic molecules, can be found in Harris (CH18)[9].  Other general classes of compounds from which fluorescence is observed. are the inorganic rare-earth compounds and various organo-metallic chelates (see [4] Chap 5 Section F). The inorganic rare-earth compounds fluoresce (from 300 to 600 nm, depending on the element) because their excited states are f-orbital based. As these electrons are sufficiently screened from their surroundings, their excited states do not suffer degradation either by chemical reaction or internal-conversion/vibration back to the ground state as, by contrast, do the transition metals.  Organo-metallic chelates are compounds in the form of a heterocyclic ring, which contains a metal ion attached by coordinate bonds to at least two non-metal ions. They therefore exhibit structural properties similar to those of fluorescent pure organic compounds (see [3] ). Their fluorescence is typically observed in the 500 to 600 nm region.
Quantitative Aspects [4] Transmitted intensity (It) can be found through the Beer-Lambert Law where;  ƒ the light of intensity (Io) is incident on a cell (length (l) = 1cm)  ƒ the cell contains a solution of absorbing substance (concentration (c) = M)  ƒ the absorbing substance has a molecular extinction coefficient (ε = dm cm-1 mol-1) at a specific wavelength   log10(Io/It)  =  εcl or alternatively,  I t  =  Io e–2.3A where A = εcl is the absorbance (or optical density) of the solution. Now by definition the quantum efficiency of fluorescence is given by:
φf = Fluorescent quanta (per sec) Absorbed quanta (per sec) = If Ia
so that  I f  =  Ia φf  =  (Io – It) φf   =  Io (1 – e–2.3A) φf Thus provided the absorbance is not too large  I f  =   Io (2.3εcl) φf (1) i.e. for a dilute solution the intensity of the fluorescence observed is proportional to both the concentration and the intensity of the exciting light.
NB; you will need to use this equation to calculate Io and subsequently find the concentration of your cigarette samples.
The error introduced by assuming the validity of this relationship at all concentrations is commonly referred to as the “inner filter effect”, i.e. the solution at the back of the cell is exposed to a lower intensity of exciting light than that at the front, owing to adsorption (or “filtering out”) of a part of the exciting light by the intervening solution. The error varies
gln/jun2000/jul2001cfh/Mar2007, ed/er/May2008 3.
proportionately to the absorbance, with an absorbance of 0.01 introducing an error of 1% in If. In some experimental geometries the fluorescent light is not gathered over the full excitation path length, but only from a central region, which reduces the error. In practical terms, one must ensure that the fluorescent intensity varies linearly with concentration i.e. before the onset of saturation.
The previous equations also indicate how spectrofluorimetry can be much more sensitive than absorption spectrometry. In  absorption spectrometry the concentration is proportional to log10(Io/It). The instrumental factor governing the minimum detectable concentration is the difference between Io and It. The strength of the light, (absolute intensity Io) is irrelevant. To achieve high sensitivity Io/It must be measured with a high degree of precision. In practice this can be done to somewhat less than one part in a thousand, giving log (Io/It) = 10–3. The maximum value of ε (for a strong band corresponding to a fully-allowed transition) may sometimes be as large as 105. Thus an estimate for the minimum detectable (molar) concentration, assuming the usual 1 cm cell, is  cmin /M ~ 10–3/1×105 = 10–8 For a spectrofluorimeter, the instrumental sensitivity is limited in principle only by the maximum intensity of exciting light available, and not by the precision with which a light intensity can measured. With photomultiplier detectors exceedingly low light intensities (If) can be measured. Thus, providing If  is not vanishingly small, by using very high exciting light intensities (Io) extremely low concentrations can be detected. With typical source intensities and other conditions (e.g. Фf, ε) favourable, concentrations as low as 10–12 M can be detected. Actual values measured both by fluorescence and absorption for a selection of PAHs are given in the following table [5].
DETERMINATION OF ENVIRONMENTAL PAHs BY FLUORESCENCE A model study on the fluorescent determination of specific PAHs in water is described in [6], while in [7] the partial identification and determination of PAHs in atmospheric particulate matter is discussed. An extensive study (though not by fluorescence) of PAHs in tobacco smoke is reported in [8]. Taken together these papers give an adequate background to the present experiment;
Table 1: _________________________________________________________________ Compound (PAH) MW    cmin Fluor /M  cmin Abs /M   φf ε    _________________________________________________________________ Anthracene 178 2.1×10–12 3300×10–12 0.31 130,000 1,2-Benzanthracene 228 5.5×10–12 4800×10–12 0.19 91,000 Fluorene 166 1.5×10–10 220×10–10 0.53 20,000 Naphthalene 128 4.3×10–10 790×10–10 0.13 5,500 Phenanthrene 178 2.0×10–11 710×10–11 0.10 61,500 _________________________________________________________________ Avg. (geom. mean) 173 2.7×10–11 114×10–10 0.21 38,000 _________________________________________________________________
EXPERIMENTAL You are supplied with 2 low tar filtered (LTF), 2 medium tar filtered (MTF), 2 high tar filtered (HTF) and 2 high tar unfiltered (HTU) cigarettes, as well as a couple of excess cigarettes to calibrate the system Mark all cigarettes 5 cm from the unfiltered end. The burning is done on a suction line which includes 2 cold traps to collect the condensate
gln/jun2000/jul2001cfh/Mar2007, ed/er/May2008 4.
from the smoke. The traps are cooled by liquid nitrogen. Insert an unlit cigarette before cooling the traps.
Initially you need to calibrate the suction system, set a good flow of water through the suction pump, insert one of the cigarettes and light it, remember to time the burn time (to the 5cm mark)
The suction should be sufficiently great that smoke is not lost, but at the same time the cigarette should not burn too fast, otherwise condensate may be lost. 2 to 3 mins is satisfactory. This is adjusted by slightly altering the air bleed (leaving the water flow constant) – once the system is adjusted to your satisfaction clean out the smoke traps and tubes before starting your actual samples.
Start your sample collection – remember- • Each “sample” consists of two cigarettes • Cool the traps for a minute before you light the 1st cigarette, and let the traps warm up after the second before touching them to avoid cold burns • Remember to rinse out the cigarette holder and trap fitting
When the 2nd cigarette has burned to the mark, remove it with the tweezers supplied. Disconnect the suction and lower the dewar flasks, allowing the traps to warm up.
Using pasteur pipettes and alternate small aliquots of hexane and water/methanol mixture, carefully wash the condensate from both traps into a 100mL separating funnel. The last wash should be water/methanol and the traps should be clean. Don’t forget to wash the cigarette holder and include the washings in the sample.
To separate the PAH’s from the water/methanol/hexane mixture: • 1) Stopper the separating funnel and shake to mix the layers • 2) Allow the layers to separate – the top layer contains PAH’s/Hexane, bottom layer methanol/water. • 3) Drain the bottom layer into a clean 50mL volumetric flask. Do not throw out yet. • 4) Drain the top remaining layer into another clean, labelled (LTF, MTF etc) 50mL volumetric. • Take the bottom layer, and re-add it to the separating funnel. Add 15mL hexane, and repeat steps 1-4 two or three times, or until the top, hexane layer is clear.  • Make the flask containing the combined hexane top layers up to the mark using hexane.  Set aside for measurement later.  • Remember – Rinse the separating funnel between samples! Dispose of solvents in the waste bucket in your fume cupboard. Don’t overfill the 50mL flask containing the hexane/sample mixture.  This entire process needs to be completed for each sample (four times in total).
Because of their high concentration, further dilution of the HTF and HTU samples is required.  Make a one-in-five dilution of both these samples by taking 2mL of the sample and making it up to 10mL with hexane in 10mL volumetric flask.
You should now have 6 samples – LTF-MTF-HTF-HTU-dilutedHTF-dilutedHTU.
CAUTION – METHANOL IS A HAZARDOUS CHEMICAL AND IS ABSORBED THROUGH THE SKIN. EXERCISE CARE WHEN USING IT.
gln/jun2000/jul2001cfh/Mar2007, ed/er/May2008 5.
Calibration curve construction: Take four 10 cm3 standard flasks. Add to them 2, 4, 6 and 8 mL of the standard anthracene solution supplied. Make up to the mark with hexane. You will also need and pure hexane and a pure anthracene standard solution.
FLUORIMETRY Before making each measurement wash the four sided cell with a little of the solution to be measured. Take great care not to get any solution on the outside of the cell, especially when emptying. Do not touch any of the four cell faces. Only handle the cell by the edges – if any solution is spilt on the outside, rinse with a little hexane and wipe carefully with tissue paper.  Take care to not spill ANY solutions in or on the instrument.   HANDLE THE FLUORESCENCE CELL WITH EXTREME CARE AT ALL TIMES. When you are finished with the cell, thoroughly rinse the cell and return it to your lab instructor.
Open the Cary Eclipse program called “Scan”.  It is first necessary to record an excitation spectrum in order to determine the optimal wavelength for excitation( ) ex max λ .  Here the excitation wavelength is scanned while the emission monochromator is held at a constant value.  Partially fill a sample cell with the undiluted anthracene solution.  ..  Select Excitation and set the excitation wavelength scan range from 300 to 395 and the emission wavelength to about 400 nm.    Run an excitation spectrum and decide on a value of ( ) ex max λ .  Next, select Emission and run an emission spectrum between 365 nm and 480 nm using this value of ( ) ex max λ to find the wavelength of maximum emission( ) em max λ .  You also need to decide on the best excitation / emission filter settings [auto?], the scan speed, the slit widths and the PMT voltage.  Finally, re-run the excitation spectrum using this value of ( ) em max λ .
Using the optimal settings, measure the emission spectra of the remaining samples in the following order:   (i) pure hexane  (ii) 2/10 diluted anthracence (iii) 4/10 diluted anthracence (iv) 6/10 diluted anthracence (v) 8/10 diluted anthracence (vi) undiluted anthracence (vii) pure hexane    (viii) undiluted LTF (ix) undiluted MFT (x) 2/10 diluted HTF (xi) 2/10 diluted HTU (xii) undiluted HTF (xiii) pure hexane  If you do not get very similar results for the three pure hexane measurements then repeat ALL measurements until you get a set of results which are consistent.
Check that the sample results (viii)-(x) lie within the linear portion of the anthracene calibration plot. If any one does not, make an appropriate dilution to obtain a result that does.  If you are satisfied with your results, then get them initialled by the Demonstrator (or the Lab Technician). Discard all samples (including water/methanol waste) into the organic waste  bottle in the fume cupboard. Carefully rinse the cell and all glassware with acetone.
gln/jun2000/jul2001cfh/Mar2007, ed/er/May2008 6.
REPORT 1. Sketch the optical system of the fluorimeter used in this experiment. Show the source lamp, the lens, the filters, the sample cell and the detector.  2. Why is the path for the fluorescence at right-angles to the source beam? 3. Compare the excitation spectrum with the emission spectrum, comment on and explain any similarities / differences in shape and wavelength.  4 Tabulate your results for emission Intensity at ( ) em max λ vs.  Concentration  and the wavelength of each peak in the Excitation and emission spectra. Which peaks correspond to the 0-0 transitions?
5. From the diluted HTF and HTU fluorescence values, calculate the corresponding ‘dilution-adjusted’ values you would expect from undiluted solutions. How does this calculated value for HTF and HTU compare with the measured, undiluted value?  Explain any discrepancy you observe.
6. Plot the anthracene calibration curve (nett fluorescence versus molar concentration; include zero concentration). Add a trend line (linear) and equation to the graph.  Comment on the shape of the curve, and the result obtained for the undiluted anthracene sample. How does this plot relate to equation (1), and the discussion of the inner filter effect? How can you now account for any difference between the dilution-adjusted and the measured undiluted HTF values?
7. Using equation (1), the data for Anthracene in table (1), and any point from the linear section of your calibration curve calculate your reference Io value.  Now, again using eq. 1, calculate the concentration “average PAH” in each cigarette sample – hint – use the Io reference value calculated above, data from table (1) and your experimental results.  Present this data in two ways – (a) compare these relative results with the tar values stated on the packets (mG per cigarette) – what are some factors that could account for errors or have effected your results? And (b), normalise your results so that HTU = 1.0. What conclusions can be made as to the effectiveness of the filters?  What assumptions are you making using the data in table (1) to calculate the average PAH in the sample?
8. From these estimates of PAH in cigarettes, and making any appropriate assumptions, comment on the amount of PAHs (in grams) released per year into (a) a smoker’s lungs, and (b) the atmosphere of the city of Melbourne. ‘
Remember your report must include an Introduction, aim, methods/materials, results/calculation, discussion, and conclusion and must be properly referenced and formatted.
REFERENCES  1. Chang, R; Basic Principles of Spectroscopy, (1971) Chapter 12. 535.84 C4566. 2. Browning, D.R., Spectroscopy (1969); Chapter 2. 3. Hercules, D.M., Fluorescence and Phosphorescence Analysis (1966). 545.812 H539f.
gln/jun2000/jul2001cfh/Mar2007, ed/er/May2008 7.
4. Parker, C.A., Photoluminescence of Solutions (1968). 535.35 P28p. 5. Cetorelli, J.J., McCarthy, W.J. and Winefordner, J.D., J. Chem. Ed., 45 (1968) 98.  6. Schwarz, F.P. and Wasik, S.P., Anal. Chem., 48 (1976) 524. 7. Fox, M.A. and Staley, S.W., Anal. Chem., 48 (1976) 992. 8. Severson, R.F., Snook, M.E., Arrendale, R.F. and Chortyk, O.T., Anal. Chem., 48 (1976) 1866.  9. Harris, C.E., Quantitative Chemical Analysis – 7th Ed. (2007) Chapter 18.

Need Help-2.3 Knowledge Check


Need Help-2.3 Knowledge Check

“The molecules in Tyler are composed of carbon and other atoms that share one or more electrons between 2 atoms, forming what is known as a(n) __________ bond.”

Ph.D admission Personal Statement


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Writing Project #1

Ph.D admission Personal Statement

Paper details

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FULL report- Chemistry


FULL report- Chemistry

Introduction:…the usual, clearly state the purpose first and then explain the chemistry involved … don’t copy the manual or just list calculations

Procedure: …the usual…full account of what you actually did in the lab in the order that you did it, written in past tense and paragraph format (i.e. full sentences) do not just copy the lab manual and change tense

Data:
– lab computer printout has absorbance data
-Also include a table of volumes of HNO3, NaSCN and Fe(NO3)3 actually used in the 5 solutions (Vi , Vf and Vused)

Calculations: (see p. 32 in manual)
-show one full set of calculations for one solution…remember to show equations used, labels, units and proper sig figs
– also show calculation of :
average Keq
average deviation (see p. 8 in manual)
% deviation (average deviation / average Keq) x 100

Discussion: – the usual…
– state the results
– compare to expected & comment
– sources of experimental error

Remember to arrange the sections in the order as listed above and attach the signed carbons to the back

CH111 PRELAB: HARDNESS OF WATER


Revised Summer II 2016

CH111 PRELAB : HARDNESS OF WATER   

  1. (a) Convert 9.13 x 10-5 g CaCO3/mL to ppm. (Hint: conversion factor on p. 17.)

 

 

 

 

 

 

(b) When titrating hardness with a soap solution, the endpoint is indicated by a lather.  This       lather is created by excess soap and a “blank” must be first determined by titrating a       sample of distilled water (distilled water has zero hardness, so the soap used is only for             the lather).

 

Calculate the “blank”  ( mL soap / mL distilled water) if a student used 0.74 mL of soap   to get a lather for a 20.00 mL sample of distilled water.

 

 

 

 

 

 

(c)   When titrating water samples with hardnesses greater than zero, the soap first reacts    with all the Ca2+ and then produces a full lather to get to the endpoint.  Therefore,       the amount of soap used for only the lather needs to be subtracted out of the total    volume of soap used for the full titration in order to determine the amount of soap   needed for the Ca2+(also called the corrected soap volume).

 

Calculate the corrected soap volume (the soap is required to react with just the Ca2+ ) if               a 10.00 mL sample of hard water took a total of 5.13 mL of soap to get to the full lather                            endpoint.

 

corrected soap volume (mL) = total mL soap used – [ “blank”(from 1b) x (mL of water sample)]

 

 

 

 

 

 

 

  1. Describe the procedure for the experiment. This could be in an outline format or a flow chart format or paragraph format.  It should not be copied directly from the manual.  (This should be between ½  – 1 page, you may use the back of the page)

 

 

 

 

 

 

  1. Briefly discuss all safety precautions related to this experiment.  (chemical and equipment related)

 

CH111

HARDNESS OF WATER

 

Chemical Handling and Waste Treatment

 

Normal laboratory safety practices must be followed at all times.  MSDS sheets are available in the laboratory.

 

The soap solution is alcohol-based and therefore can be considered flammable.  No sparks or flames are allowed in the laboratory.

 

The  EBT  (eriochrome black T)  indicator  is  dissolved  in 2-methoxyethanol.  This solution is a combustible liquid and is considered harmful if inhaled, swallowed or absorbed through the skin.  If skin contact occurs, promptly wash with soap and water.

 

The pH 10 buffer solution has a very high ammonia concentration, the vapor is very noxious and especially corrosive to skin and eyes.  Avoid excessive inhalation, however if you do inhale the vapor, move away from the area to fresh air.  Contact lenses SHOULD NOT BE WORN.  If skin contact occurs, flush the affected area with lots of cold tap water and inform the instructor.

 

All completed titrations, can be disposed of by rinsing down the drain with lots of cold tap water.

 

Due at beginning of lab

ALL parts EXCEPT PROCEDURE

with SAFEASSIGN

(title page)

 

Introduction…as usual…state the purpose and explain the chemistry involved…do NOT just list all the calculations in the intro

 

Data: simply use lab computer print-out…be sure to attach it in the data section (NOT AT END)

 

Calculations: show all the calculations…there were 7 titrations…so show 7 equations and 7 calculations and 7 answers…be sure to give the equation used, use labels, units and proper significant figures.

 

Discussion: State the ppm results for the water samples (tap and unknown) for the 2 methods. Compare to the actual given values and compare the 2 methods to each other. % error is a good way to compare the 4 results. Comment on accuracy and precision.  Discuss sources of experimental error.

(signed carbons attached at end)

 

 

 

CHEMISTRY LABORATORY GENERAL INFORMATION

This laboratory course is intended to present the basic concepts that are essential to a general understanding of the science called chemistry. The specific objectives are:

  1. Provide training in the application of specific principles, thus strengthening the power of logical reasoning.
  2. Develop an ability to discover facts through experimentation, an important step in learning to evaluate the work of others.
  3. Develop a feeling for quantities, such as the volume or mass of a substance used in the laboratory, or the degree of completeness to which a reaction proceeds.
  4. Identify and induce neat and precise work habits.
  5. Develop the ability to produce well-written prose which conveys the method of experimentation, the results of that experimentation, and the logic by which the results of the experimentation are analyzed.

Notebooks for the Laboratory

Each student is required to have a laboratory notebook. The laboratory notebook is a permanent, documented record of laboratory data and observations. The laboratory notebook must be a bound book. The notebook makes carbonless copies. This notebook should be a complete record of the ideas and actions which are part of the laboratory work. Keeping a proper laboratory notebook is an essential part of “real-life” science and research. Some specifics which have been developed over the last couple of centuries as part of the format for a laboratory notebook are given below:

  1. Each page number is pre-printed in the upper right-hand corner, use pages in numerical order as printed. Do not skip pages or tear out random pages.
  2. Your name, the date, the name(s) of your lab partner(s) (if any) and the title of the experiment should be recorded on every page used for the experiment. This should be done during the lab period while using the lab notebook.
  3. Only one side of each page is used. A carbon copy must be generated simultaneously. When using the carbonless notebook, be sure to put the cardboard separator between each set of pages.
  4. All data, calculations and details of the experiment must be recorded directly into the notebook, in ink, while you are performing the experiment. It is important that every detail is recorded as the event occurs. The notebook is a historical record, a diary, of what was actually done in the lab. Information is never collected on scraps of paper, the lab manual or other paper to be recorded

“later”. Always use the lab notebook for primary data recording.

  1. Both the original and the carbon copy pages must be initialed and dated by the instructor before you leave the laboratory. The carbon copy (the bottom copy) is perforated and is removed from the notebook to be taken home and is used as the basis of your final report. Never remove the original pages from the notebook. The laboratory notebook itself must remain in the laboratory drawer.

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– General Information –

  1. Since data and thoughts are being recorded directly into the notebook, errors will be made. These errors are deleted by drawing a single line through them. Never blot out or erase or “white-out” what are considered errors. Original thoughts and data must not be destroyed! These so-called errors often provide useful information. You should also record a brief explanation of why the item was changed.
  2. When calculations are recorded in the lab notebook, be sure to clearly identify the calculation, show equations used, labels and units as well as the worked out answer. If a calculation is incorrect and has to be re-done, be sure to show the new work. As with correcting data, just draw a single line through the error and place the new entry nearby.
  3. A laboratory notebook should be legible and the data should be easily decipherable with labels and units.

Plagiarism of any kind will not be tolerated. Copying from any text, the manual or any other person will not be accepted. Each student is expected to write and submit a unique report that represents their own ideas. Group work should not result in identical reports. Any instance of plagiarism or re-use of data (past or present) without consent of the instructor will seriously jeopardize your lab grade. It is important to remember that if you fail lab you fail the whole course.

The issue of digital plagiarism has raised concerns about ethics, student writing experiences, and academic integrity. Although you may never have engaged in intentional plagiarism, many students do incorporate sources without citations, which is a form of plagiarism. The University of Hartford subscribes to a digital plagiarism detection program called SafeAssign, which you will use to check lab reports for this course and see whether you may have included in your report material that requires a citation. In addition to the actual report, you will upload your work to Blackboard through SafeAssign so that it can be checked against web pages and databases of existing papers. Your paper will then automatically become part of that database for future use. Further instructions will be given in lab.

In addition to the universal rules banning any form of plagiarism, in the scientific disciplines, particularly with respect to patents, the intellectual ownership and correct representation of data are of utmost importance. Thus it is considered to be extremely unethical to use another person’s data, with or without that person’s permission, unless the data are clearly identified as being collected by a different person. It is unethical to “fudge” data or make up data. Every time an experiment is performed, it is a unique demonstration of a chemical principle. As such, it is unacceptable to present data that were collected on one day as data that were collected on a different day. Data from one run of an experiment may not be “reused” for a second run, even if the same person is performing the experiment. Data may not be added or eliminated from a data set without an explanation and justification.

There are a number of sources which expand upon these general principles. If a student is uncertain whether a certain behavior or use of data is scientifically ethical, it is the responsibility of the student to ask the laboratory instructor in advance.

Written Presentation of Your Work

All presentations of experimental work should be written in the past tense, since you have already done the experiment. A somewhat more involved concept is that of writing in the third-person passive voice. This formality is derived from the fact that the role of the experimenter in the laboratory is to make it possible for the natural course of events to take place. Thus, the experimenter does not actually react one chemical substance with another. As long as the procedure is strictly followed, the given reaction

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should take place in the same way, no matter who has brought the two species together (assuming competence on the part of the researcher)! So, instead of writing a description as “I mixed 15.0 mL of 1.03M acetic acid with 23.2 mL of 0.923M sodium hydroxide…”, it should be “Fifteen (15.0) mL of 1.03M

acetic acid were mixed with 23.2 mL of 0.923M sodium hydroxide…”. Nature will take it’s own course regardless of the personality of the experimenter, so no personal pronouns will appear in your writing. Finally, the reader should be led through your report one thought at a time. Even calculations need to have some words around them to lead the reader through your thoughts as the calculations are done.

A typical lab report has numerous sections. Pay attention to specific weekly report requirements (posted of BlackBoard) for each individual experiment, as not every report is a full one.

  1. The TITLE PAGE includes (as a separate page !)
    1. the title of the experiment (as written in the manual)
    2. the date(s) of the experiment
    3. the date the report is submitted
    4. name of the student submitting the report
    5. the name(s) of any partners for that experiment (if applicable)
  2. The INTRODUCTION should literally introduce the entire experiment. The first paragraph should present an overview of the experiment. In this paragraph briefly present the purpose of the experiment and the key experimental technique to be used. Any theory behind the experimental procedures or objectives should be presented in the introduction. Any expectations for the results can be presented. Important equations (chemical and algebraic) which are to be used during the experiment should be presented or derived (only if the equation was not derived in the lab manual) in the introduction Do not simply give a list of equations. Do not actually perform the calculations or state the results obtained. Keep in mind that you are trying to instruct the reader so that they will understand all the details and implications of the experiment during the rest of the report. Functionally, it is usually easiest to write this section last, since it is easier to write an introduction when you already have finished what you are going to introduce!
  3. The PROCEDURE section should be a detailed description of what actually happened during the experiment. It should include all procedures and observations. This section must be a faithful history of your experience in the laboratory (thus, as always, written in the past tense and the third- person passive voice). Your laboratory notebook should be your guide in writing this section. This section is in paragraph format, NOT simply a numbered or bulleted list of directions. The reader wants to know what you did and what you experienced, to a level of detail that the experiment could be exactly duplicated from you written word. It is your job to transport the reader to the laboratory to relive your experience. Specific data values and calculations should NOT be included in this section.
  4. The DATA, CALCULATION and GRAPH sections should be an orderly presentation of your primary data. Primary data are those values provided by the experiment, before they are used for any calculation. Thus, if a buret reading before a titration is 4.56 mL, and the reading after the titration is 45.94 mL, these two values are the primary data. The 41.38 mL which were delivered from the buret is a calculated quantity. It is necessary to calculate and present the 41.38 mL, but it would not be sufficient to report only the 41.38 mL value.

Data are generally organized into tables. Each table should be numbered and given a name (title). In many experiments, data are checked through interaction with a specifically- tailored computer program. These programs generally provide a print-out of all or part of the data for the experiment. The computer print-out should be used as all or part of the data section, as appropriate. Attach the

printout in the appropriate section in the report.

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– General Information –

Calculations: Before you actually write down an equation and solve for the desired quantity, your prose should indicate what it is that you will be calculating, and how. Then when you actually make the calculation, the reader will know what you are doing and thinking. As mentioned above, it is your job to continually lead the reader through the thoughts that are the logical development of the experiment and analysis. While all calculations are expected to be initially carried out in the lab notebook. The carbon copies of these pages which are attached to the final lab report are only used to evaluate your performance and do NOT qualify as the calculation section of your formal lab report. You should show the calculations neatly in this section using proper number of significant figures and label all units. Be sure to label each calculation with text (not just a sequential set of numbers). Give the equation used and show the worked out calculation with your data. Proper units and significant figures must always be used.

Any graphs necessary for the analysis of the data should be computer-generated. Sketches constructed from plain lined paper or on pages from the lab notebook are NOT acceptable. The graph should be a full page and the plotted points should be clearly shown and use up most of the page (not all squished into a corner). In general, each axis must be labeled, and each label must contain the dimension of that label (e.g. mL, C, sec, etc.). There generally should be from 4 to 6 demarcations on each axis (i.e. mL readings might be 10, 20, 30, 40, and not 1, 2, 3, 4…40 even though there may be 40 ruled lines comprising the axis). The demarcations should be some convenient number, usually a number easily divisible by 2 or 5. Data points should never be connected with a line unless that line is the result of calculation from a function which represents the data (i.e. best fit line or trend line). So, if the data are theoretically supposed to represent a linear function, it is perfectly acceptable to draw the best straight line superimposed upon the data. It is not acceptable to connect them as if it were a four-year-old’s connect-the-dots book. Any graph made during the lab period can be used in the report provided it is signed by the lab instructor and follows the specifications listed.

  1. The DISCUSSION section is the place where you discuss the outcome(s) of the experiment. All good experiments start with a certain expectation. This expectation should have been presented in the introduction section. Firstly, state your result(s), compare your result(s) with the expectation(s) and/or the true value and comment on this comparison. And finally discuss 3-4 possible sources of experimental error and how those errors could have affected the results of the experiment.

One part of your expectations involves the quality of your data. Since each measurement has a random uncertainty associated with it, there is an expectation that there will be some uncertainty (error) in your results. So, if all your measurements were made to 4 significant figures, and your data deviate from some expected value in the second significant figure, some part of the procedure either has a larger uncertainty than was immediately obvious, or there was some non-random error involved in the experiment (e.g. the solution was spilled over the bench top just before the final measurement!). The laboratory experiments are designed to bring you through numerous common scenarios involving different experimental uncertainties. Analysis of experimental uncertainty is constantly done by working scientists and engineers.

  1. The carbon copies of the notebook pages, initialed by the instructor, are attached at the end of the report. In the event that this cannot be done for a particular experiment, the instructor should be notified and some alternate arrangement made, before submitting the report. Without these pages, the report is considered incomplete and cannot be given a grade.

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Grading: The grade for each laboratory experiment in CH110 is calculated as follows:
1. The first 15% of the grade is based upon a Pre-Lab exercise to be submitted at the start of the

laboratory session, they will not be accepted late.
NOTE: The pre-lab questions are available on http://blackboard.hartford.edu in the CH110 ALL LABS

course. It is your responsibility to obtain them and submit them according to the schedule.

A video is available on Blackboard for each experiment with additional information. It is highly recommended that you read through the experiment write up in the manual and watch the video before attempting to complete the pre-lab.

This “pre-lab” consists of:

  1. a)
  2. b)
  3. c)

Answers to questions about the experiment. These questions are designed to prepare you for the experiment. They might include sample calculations with typical data, or they might be a definition or short answer-type question. Show your work for any calculations; do not copy any source or the manual for short-answer questions. If you are unable to answer any of these questions, it would be to your great advantage to get help well in advance of your lab period. A clear understanding of the pre-lab questions will be a tremendous asset to you during the experiment itself.

A brief description of the procedure for the experiment. This could be in an outline format or a flow chart format or paragraph format. It should not be copied directly from the manual. This part should be between 1⁄2 and one page.

An analysis of the safety procedures and disposal requirements specific to that experiment. It is not intended that every item from the safety contract be repeated. However, each experiment has specific safety and disposal details which should be summarized in this section.

The next 35% of the grade is based upon your performance during the laboratory period including, but not limited to, following safety guidelines, your general technique, appropriate care of measurement and understanding of the number of significant figures associated with each measurement, neatness, efficiency, considerations for fellow students, attitude, promptness to class, proper use of the laboratory notebook pages and accuracy of the results when appropriate.

The last 50% of the grade is based upon the finished report. This grade is based on the clarity of presentation, neatness, logical discussion and interpretation, correct calculations and their presentation, grammar, spelling, punctuation, use of the correct tense and voice. Lab reports are due at the next lab meeting. Late submissions will be penalized 10 points per week (pro-rated on a daily basis). Note: not every report will be a full written report; you are expected to follow the criteria provided by your lab instructor each week. In addition, some reports are required to be submitted to SafeAssign for plagiarism review, the report grade will receive a penalty if plagiarism is present or if the report is not submitted to SafeAssign.

Attendance at all laboratory periods and submission of all reports will result in the dropping of the lowest NON-ZERO grade upon calculation of the final laboratory average at the end of the semester. If an excused absence has occurred during the semester, that “grade” will be dropped. An unexcused absence is considered a zero (see below) and will not be dropped at the time of final-grade calculation.

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– General Information –

Absences

Unexcused or missed lab sessions will be graded as a zero. If you miss a lab, you must contact your lab instructor and the lab supervisor immediately with documentation for your absence. In general, make-up labs will not be arranged. However, if you have a serious reason for an absence, it might be possible, with permission of the lab supervisor  to arrange for you to go to another lab section to do the experiment during the week the same experiment is scheduled. This must be arranged in advance. Excused absences can only be granted by the laboratory supervisor.

Student-Athletes should provide a copy of their practice/game schedule to their lab instructor or lab supervisor at the beginning of the semester or the beginning of their season.  with any questions.

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LABORATORY SAFETY CONTRACT

University of Hartford – Chemistry Department

  1. Eye protection must be worn at all times in the laboratory. Failure to do so will result in expulsion from the laboratory. Acceptable safety goggles are supplied upon check-in for CH110 and are the students’ responsibility for subsequent lab courses, additional pairs are available for purchase from the chemistry department.
  2. SMOKING IS ABSOLUTELY PROHIBITED at all times in the laboratory and in the building.
  3. Eating and drinking are not permitted in the laboratory. This includes candy and gum. Water bottles or any beverage or food container must be stored in a closed backpack away from the lab bench areas.
  4. Cell phones or any other type of personal communication device may not be used during the laboratory period. These devices should be turned off for the duration of the lab period, (i.e. you will not receive nor make calls or text during the lab period). Also, iPods or any other types of personal listening device with ear/head phones are not allowed during the lab period.
  5. Horseplay, pranks and other acts of mischief are especially dangerous and are absolutely prohibited. Do not sit on laboratory bench areas. Place all personal belongings in designated area, keep bench area and floor clear of excess items such as books and bags. Use the wall hooks for coats, etc.
  6. Shoes must be worn in the laboratory at all times; sandals are not permitted. Rollerblades, “Heelys” or skateboards are NOT allowed in the laboratory at any time. Tie back long hair and loose clothing when in the laboratory. Shorts are not recommended.
  7. Students must be acquainted with the location and use of the following safety equipment: fire extinguisher, fire blanket, safety shower, eye wash fountain(s), emergency gas shut-off and exit from the laboratory. In any emergency, call the lab instructor immediately.
  8. Students are NOT permitted to enter the stockroom to obtain supplies. Any necessary item will be issued by the lab instructor or stockroom attendant.
  9. DISPOSAL: Used paper and towels should be placed in the large trash barrels. Broken glass should be placed in the glass disposal boxes. Any solid chemicals or metal items will be disposed of as directed by lab instructor. No solids are allowed in the sink; water-soluble liquids only may be poured down the drains. If in doubt, check with the instructor.
  10. All spills must be cleaned up immediately; this includes your work area, in the hoods, on side benches, near the balances and the floor. For spills inside the balance, consult the instructor.
  11. Mouth suction must never be used to fill pipets. Never taste any chemical or put it in your mouth. Wash hands thoroughly when finished with experiment.
  12. Never use chipped or broken glassware, obtain a new item from stockroom.
  13. Never leave an experiment unattended, particularly an open flame.
  14. Chemicals (reagents or products) may NOT be removed from the laboratory.
  15. At the end of each laboratory period, each student must clean his/her bench area with a wet sponge.
  16. All laboratory work in this course must be done during a regularly scheduled lab period with a lab instructor in attendance.

I HAVE READ, UNDERSTAND AND WILL FOLLOW THE ABOVE SAFETY RULES. I HAVE ALSO BEEN MADE AWARE OF THE LOCATION AND USE OF THE SAFETY EQUIPMENT.

Student signature CH course #

Date Lab Instructor

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Selected Techniques and Procedures

  1. Simple Statistics

The average or mean of a set of values can be calculated be taking the sum of the values, and dividing by the number of values. The average of the molarity in the following example is calculated,

average = 0.1212 + 0.1225 + 0.1217 = 0.1218 3

The precision of a set of values refers to the closeness of approach of the set of values to a common value (the average). Precision may be measured in terms of the deviations of the individual measurements of a series from the average value of that series. The average of the absolute values of the individual deviations is called the average deviation.

Example: In a series of titrations, the following values for the molarity of a solution were found:

(1) (2) (3)

Values 0.1212 M 0.1225 M 0.1217 M

Deviation from the Average

(0.1212 – 0.1218) = – 0.0006 (0.1225 – 0.1218) = + 0.0007 (0.1217 – 0.1218) = – 0.0001

Absolute Value of the Deviation

+ 0.0006 M + 0.0007 M + 0.0001 M

= 0.0014 ÷ 3
= 0.0005 M (Avg dev)

=

0.3654 ÷ 3 = 0.1218 M

(Avg Molarity)
Thus the molarity may be reported as 0.1218 M ± 0.0005 M.

Percent deviation is a convenient way to express the precision results. Percent deviation is easily determined by dividing the average deviation by the average value and multiplying by 100.

% dev = avg dev x 100 % dev = 0.0005 x 100 = 0.41 % dev average 0.1218

Accuracy refers to the nearness of a determination to the accepted value. Often this can be expressed by percent error. The percent error can be found by dividing the difference between the accepted value and the experimental value by the accepted value and then multiplying by one hundred.

Example: In an experiment, a student calculated a value for Absolute Zero to be -256°C. The accepted value for Absolute Zero is -273°C.

% error = accepted – experimental x 100 accepted

% error = (-273°C) – (-256°C) x 100 = 6.2 % error (-273°C)

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– General Information –

  1. Use of a Bunsen Burner
    • –  Close the thumbscrew and open 1/4 turn.
    • –  Close the air holes with the moveable sleeve.
    • –  Open the gas valve on the inlet pipe wide.
    • –  Light the burner with the striker.
    • –  Regulate the thumbscrew and the sleeve to produce a blue flame with a sharp pointed inner blue cone. (Note: The gas valve on the inlet pipe is not used to regulate gas flow. It should be used as an on/off valve only.)
    • –  A bright yellow tip indicates insufficient air. Open the sleeve to let in more air.
    • –  If the flame lifts off the burner (common when using a flame spreader), turn down the gas with the thumbscrew.
  2. Use of Pipets

Rinse the inside of the pipet by drawing in several milliliters of distilled water with the aid of a pipet bulb or pump, shaking, and then expelling all liquid from the pipet. As always in pipetting, take care that you do not draw any liquid into the pipet bulb or pump. If this does occur, remove the bulb or pump from the pipet and expel the liquid into the sink. If you draw some liquid other than water into the bulb or pump, rinse the bulb or pump by drawing water into it and thoroughly expelling all liquid. After the pipet is thoroughly rinsed, dry the outside of the pipet tip and draw several milliliters of the solution to be transferred into the pipet. Never place a pipet directly into a stock bottle, pour some of the solution into a beaker or graduated cylinder first. Rinse the pipet carefully with the solution by shaking, and discard the rinse solution. Do this once more, then fill the pipet to a few centimeters above the mark on the upper portion of the stem. Remove the bulb or pump and quickly place a finger or thumb over the top of the pipet. Allow the liquid meniscus to align with the mark on the pipet by slowly and carefully moving your finger off the pipet. If the meniscus drops below the line, use the bulb or pump again to draw the liquid up. When the meniscus is on the line, wipe the tip of the pipet, touch the tip of the pipet to the side of the container to which you wish to transfer the solution, and allow the liquid level to drain. With a singular volume pipet, the liquid should be allowed to drain, and the tip kept on the side of the flask 3 seconds after the solution has ceased flowing. The remaining liquid in the tip is NOT to be blown out by the pipet bulb.

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  1. Use of Burets

Before use, a buret should be thoroughly cleaned with soap solution and a long brush. The cleansing should be followed by a thorough rinsing with distilled water. If any water droplets adhere to the inner wall of the buret, it is not clean and should be re-cleaned. With the stopcock closed, add about 5 mL of the solution to be measured. Rotate the buret to wet the walls. Allow the liquid to drain through the stopcock. Repeat this rinse one more time. Clamp the buret to the ring stand with a buret clamp. Fill the buret above the zero mark with the solution. Allow the buret to drain past the zero mark to fill the tip with solution. Do not try to drain it to exactly zero as this introduces prejudicial error. Make sure no air bubbles are left in the tip or on the walls of the buret. Bubbles on the wall may be dislodged by gently tapping the sides of the buret. Note the initial position of the meniscus. Allow the solution to drain until either an endpoint is reached in a titration, or the desired volume of solution has been delivered. Note the final position of the meniscus. The exact volume delivered is the difference between the initial and final readings. Always read buret volumes to ±0.01mL.

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Erlenmeyer flask

Florence flask

beaker

test tube brush

watch glass

test tube holder

test tubes

graduated cylinders

tongs

test tube rack

evaporating dish

tripod

ring stand

funnel rack clamp

clamp holder

11

pipets

Bunsen burner buret clamp

volumetric flask

flame spreader

buret

ring

12

 

 

 

 

CHEM 3322 – Ultra High Pressure Liquid Chromatography Mass Spectrometry


CHEM 3322 – Instrumental Methods of Analysis

Ultra High Pressure Liquid Chromatography Mass Spectrometry

Some general guidance on Laboratory Reports:

Format, Guidance and Grading Criteria Reports should be 1.5 lines spaced. Word and page limits should be maintained.

Abstract: (Maximum 200 words) Summarize in a concise paragraph the purpose of the report, data presented and major conclusions. What was done, why was it done, how was it done, what were the results and what conclusion(s) can be reported? Analytical abstracts must contain actual values when available. Read a few abstracts from published papers for additional guidance. Introduction: (1 page max) • Define the subject of the report: “Why was this study performed?” • What is the significance and relevance? In other words, why did we do this? • Outline scientific purpose(s) and/or objective(s): “What are the specific hypotheses and the experimental design for investigation?” Materials and Methods: (2 page max) • List chemicals used, any preparation required, who made them (vendor) and their concentration, purity and lot number where appropriate. • List all equipment used (instrumentation, columns etc.). Listing common equipment like glassware is not required. • Provide step-by-step procedure with enough detail for the reader to understand the experiment. Make sure to note weights, volumes, and any special glassware and equipment where appropriate. Results: (Page length as needed) • Concentrate on general trends and differences and not on trivial details. • Summarize the data from the experiments without discussing their implications • Organize data into tables, figures, graphs, etc. as needed. • Provide titles for all figures and tables; include a legend explaining symbols, abbreviations, or special methods if necessary. • Number figures and tables separately and refer to them in the text by their number, i.e. 1. Figure 1 shows that the activity…. 2. The activity decreases after five minutes (fig. 1) Discussion: (2 pages max) • Interpret the data; do not restate the results • Relate results to existing theory and knowledge • Explain the logic that allows you to accept or reject your original hypotheses • Speculate if necessary but identify it as such • Provide an explanation for poor or unexpected results. Put some thought to what may have caused these results Conclusions: (1 Paragraph) • Summarize the laboratory exercise and final outcomes Additional Guidance Length Reports are typically 4-8 pages in length including the title, data and references. Rarely if ever below 5 pages and occasionally above 8-10 pages if a significant amount of data/chromatograms are requested. Do not ever exceed 15 pages per report. Double spacing, large font and other ‘creative’ efforts to make the report appear longer are not impressive to the reviewer. Great reports are not necessarily long reports. Brevity in scientific writing is an important skill to master. General Appropriate grammar and readability of reports is required. If you have concerns with your ability to write effectively in English you must seek help from outside of this course. Please let me know if you have any questions. Abstracts for analytical reports should contain actual values/results and should not exceed 200 words. I want to know what you did in the experimental section, not just cut/paste from the lab manual and use of words such as approximately to describe amounts such as volumes and weights. Lab reports must be written in MS Word and submitted electronically through TurnItIn in Blackboard. Please use the convention M8G4Hall (Module #, Group #, Last Name) when naming files. Some guidance on point values and issues to look out for with laboratory reports: Note: This list is not all-inclusive but represents some of the most common errors and resulting point deductions. 1-point deductions: 1-point, Typos/Misspellings/Incorrect language, grammar 1-point, use of colloquial/non-scientific language 1-point, name and module number not provided on report 1-point, proper labeling of figures below and tables above 1-point, proper referencing 1-point, minor technical issues 1-point, incorrect filename convention 3-point deductions: 3-points, Questions must be written out and answered in a defined section of the report Variable Point Deductions: 1-5points, the manufacturer/model of all instruments as well as solutions prepared or provided must be included in the materials/methods section. Whenever possible organize consumables into tables or bullet points rather than embedded within a paragraph. 3-5points, Moderate to significant technical issues/concerns 3-5points, 200 word limit for abstract. <100 = -3, <50 = -5, >200 = -3, >250 = -5 3-5points, discretionary. Limited discussion. Lacking pertinent information.

CHEM 3322 – Instrumental Methods of Analysis


CHEM 3322 – Instrumental Methods of Analysis

Reports should be 1.5 lines spaced. Word and page limits should be maintained.

Abstract: (Maximum 200 words)

Summarize in a concise paragraph the purpose of the report, data presented and major conclusions. What was done, why was it done, how was it done, what were the results and what conclusion(s) can be reported? Analytical abstracts must contain actual values when available. Read a few abstracts from published papers for additional guidance.

 

Introduction: (1 page max)

  • Define the subject of the report: “Why was this study performed?”
  • What is the significance and relevance? In other words, why did we do this?
  • Outline scientific purpose(s) and/or objective(s): “What are the specific hypotheses and the experimental design for investigation?”

 

Materials and Methods: (2 page max)

  • List chemicals used, any preparation required, who made them (vendor) and their concentration, purity and lot number where appropriate.
  • List all equipment used (instrumentation, columns etc.). Listing common equipment like glassware is not required.
  • Provide step-by-step procedure with enough detail for the reader to understand the experiment. Make sure to note weights, volumes, and any special glassware and equipment where appropriate.

Results: (Page length as needed)

  • Concentrate on general trends and differences and not on trivial details.
  • Summarize the data from the experiments without discussing their implications • Organize data into tables, figures, graphs, etc. as needed.
  • Provide titles for all figures and tables; include a legend explaining symbols, abbreviations, or special methods if necessary
  • Number figures and tables separately and refer to them in the text by their number, i.e. 1. Figure 1 shows that the activity…. 2. The activity decreases after five minutes (fig. 1) Discussion: (2 pages max)
  • Interpret the data; do not restate the results
  • Relate results to existing theory and knowledge
  • Explain the logic that allows you to accept or reject your original hypotheses • Speculate if necessary but identify it as such
  • Provide an explanation for poor or unexpected results. Put some thought to what may have caused these results Conclusions: (1 Paragraph)
  • Summarize the laboratory exercise and final outcomes Additional Guidance Length Reports are typically 4-8 pages in length including the title, data and references. Rarely if ever below 5 pages and occasionally above 8-10 pages if a significant amount of data/chromatograms are requested. Do not ever exceed 15 pages per report. Double spacing, large font and other ‘creative’ efforts to make the report appear longer are not impressive to the reviewer. Great reports are not necessarily long reports. Brevity in scientific writing is an important skill to master. General Appropriate grammar and readability of reports is required. If you have concerns with your ability to write effectively in English you must seek help from outside of this course. Please let me know if you have any questions. Abstracts for analytical reports should contain actual values/results and should not exceed 200 words. I want to know what you did in the experimental section, not just cut/paste from the lab manual and use of words such as approximately to describe amounts such as volumes and weights. Lab reports must be written in MS Word and submitted electronically through TurnItIn in Blackboard. Please use the convention M8G4Hall (Module #, Group #, Last Name) when naming files. Some guidance on point values and issues to look out for with laboratory reports: Note: This list is not all-inclusive but represents some of the most common errors and resulting point deductions. 1-point deductions: 1-point, Typos/Misspellings/Incorrect language, grammar 1-point, use of colloquial/non-scientific language 1-point, name and module number not provided on report 1-point, proper labeling of figures below and tables above 1-point, proper referencing 1-point, minor technical issues 1-point, incorrect filename convention 3-point deductions: 3-points, Questions must be written out and answered in a defined section of the report Variable Point

Deductions: 1-5points, the manufacturer/model of all instruments as well as solutions prepared or provided must be included in the materials/methods section. Whenever possible organize consumables into tables or bullet points rather than embedded within a paragraph. 3-5points, Moderate to significant technical issues/concerns 3-5points, 200 word limit for abstract. 200 = -3, >250 = -5 3-5points, discretionary. Limited discussion. Lacking pertinent information.

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Module 14 – Instrumental Analysis Lab (Jared Auclair, Ph.D.)

Intact Protein Analysis of Ubiquitin, Myoglobin, and Bovine Serum Albumin using Ultra High Pressure Liquid Chromatography Mass Spectrometry Background Biopharmaceuticals are gaining front-page attention with the recent FDA approval of the first biosimilar drug, Zarzio®, a biosimilar version of Amgen’s Neupogen®. A principle component of FDA drug approval is analytical characterization using mass spectrometry. In particular, using protein mass spectrometry to validate the quality of protein drugs. The mission of the Biopharmaceutical Analysis Training Laboratory (BATL) is to train scientists in protein mass spectrometry and then apply those skills to real world problems in biopharmaceutical analysis. Of utmost importance in the analysis of proteins using mass spectrometry is to ensure that there are no clinically significant differences between different lots of protein drugs. Thus, protein mass spectrometry allows us to analyze the intact mass of a given protein along with any given posttranslational modifications that may be present (eg. glycosylation, phosphorylation, amongst others). This information is vital in determining the quality of a given protein. Objective In this laboratory module we will explore a variety of proteins (ubiquitin, myoglobin, and bovine serum albumin). We will cover the preparation and analysis of these samples and considerations that need to be taken into account for proper analysis. In addition, we will modify these proteins with hydrogen peroxide and look for oxygen modifications in the intact mass spectrum. We will analyze the samples by UPLC-MS and interpret the resulting data. Safety Considerations As with all laboratory experiments personal protective equipment should be used including: a lab coat, goggles, and gloves. No open toe shoes or shorts will be permitted in the lab. Experimental Design Considerations Part #1: Preparation of samples for LC-MS analysis Ubiquitin ~ 8 kDa; Myoglobin ~15 kDa; BSA ~ 66kDa Part #2: Ubiquitin, Myoglobin and Bovine Serum Albumin Analysis: unmodified and modified. Each lab group should analyze an unmodified protein (either Ubiquitin, Myoglobin, or BSA) and a modified form of the same protein. Part #3: Interpretation of data. Critical Instrument Parameters Experimental Design Each student will conduct each of the sections with the supervision of the instructor. Data will only be shared amongst the members of the lab group (2-3) present on the day of the BATL visit. Each student will report on their own data and the data obtained by their lab partner. Data will not be shared amongst all members of the lab group. (1.1) Preparation of the Intact Protein: Desalting 1. Take a Millipore Amicon Ultra-4 with a 10,000 Da molecular weight cut-off and fill it with 4 mL 10 mM ammonium bicarbonate, pH 8.0. 2. Add 50 µL 10 mg/mL protein solution (Ubiquitin, Myoglobin or BSA) to the amicon. Cap the tube and invert 3 times to mix your sample. 3. Spin for 20 minutes at 3500 RPM in the swinging bucket centrifuge. Note: the maximum speed for this rotor is ~3800 RPM. 4. After the 20-minute spin, remove the filter ensuring the sample stays in the filter part of the amicon and decant the liquid that passed through the filter into the sink. 5. Add 4 mL of HPLC water to the amicon tube (top filter part) and resuspend by inverting. 6. Spin for 20 minutes at 3500 RPM in the swinging bucket centrifuge. 7. Repeat steps 4-6, 3 more times. In an effort to save time, during Step 6 (centrifugation), move to Step 1.2 below. 8. After the last spin the final volume of sample your sample should be 50 µL. As the sample loss is usually minimal, we’ll assume the concentration remains at 10 mg/mL. 9. Prepare a 1 mg/mL stock of your protein by diluting a 10 mg/mL stock 1:10: add 2 µL of the 10 mg/mL stock to 18 µL of HPLC water. (1.2) Preparation of the oxidized sample: Prepare your oxidized protein by incubating with hydrogen peroxide. Incubate a 10 mg/mL protein sample with 10 mM hydrogen peroxide for 1 hour at room temperature. Incubate 10 µL of 10 mg/mL protein with 1 µL of 100 mM hydrogen peroxide. After the one-hour incubation spin in the microcentrifuge for 5 minutes at 14,000 RPM to pellet any precipitate. Prepare a 1 mg/mL stock of your protein by diluting a 10 mg/mL stock 1:10: add 2 µL of the 10 mg/mL stock to 18 µL of HPLC water. (1.3) Calibration of the Waters Xevo G2S Q-Tof: Sodium cesium iodide clusters will be used to calibrate the Q-Tof using direct injection from the “C” injection valve. Using the instrument parameters from above, we will calibrate the instrument in the intact protein mass range of 500-4000 m/z using the instruments calibration sequence. (2.1) Ubiquitin, Myoglobin and Bovine Serum Albumin Analysis: unmodified and modified: Each individual will place 10 uL of their 1 mg/mL unmodified protein sample in an autosampler vial with a preslit cap and 10 uL of their 1 mg/mL modified protein sample in a separate autosampler vial with a preslit cap. Then add them to the sample manager and take note of which position you placed your tubes. We will run your samples using a C18 reverse phase column and the gradient below. Note: buffer A is water/0.1% formic acid and buffer B is acetonitrile/0.1% formic acid. Each student will add their samples to the sample table using a sample name to include their initials, date, and protein. The injection volume will be 2-3 uL per sample (2-3 ug total protein injected). (3.1) Interpretation of data: Data will be manually interpreted where possible. This will include a discussion of the charge state distribution, determining individual charge states, and how to calculate molecular mass using this information ([m/z * z]-z). In this case, the instructor will use previously collected data from SOD1. In addition, we will discuss determining a theoretical mass for your protein using uniprot.org and expasy.org. Also, we will use the maximum entropy 1 function to have the computer software deconvolute our data and translate into the mass domain (Da). Results, Calculations and Discussion 1.) What is the importance of sample preparation? Why did we desalt your sample? 2.) Calculate the theoretical molecular weight of your protein to two decimal points. 3.) Identify the charge state distribution associated with your unmodified protein? Use this information to calculate the molecular weight of your protein; select the most prevalent peak and any other smaller (modified) peaks. How does this compare to your maximum entropy deconvoluted molecular weight? How does this compare to your theoretical molecular weight? What modifications do you see (in daltons; eg +32 Da, etc.)? What might they be? 4.) Answer the same questions from number 3 for your modified sample. Did the hydrogen peroxide treatment change your protein in any way? Do you think oxidation of your protein will affect its function? 5.) If your total ion chromatogram wasn’t well resolved (you had overlapping proteins eluting at the same time) what might you do to get better resolution? 6.) What role does protein mass spectrometry play in modern day biotechnology? Report Data LC/MS data (2 total chromatograms and selected MS data) should be included in the report for all sections of this lab.

Uranium; Research Paper


Uranium; Research Paper

Uranium

 

Introduction

As new technologies continue to emerge, the world power consumption rates continue to go up. This is because these new technologies use electric power to operate and perform their functions. This consequently means that the available power sources continue to become insufficient. Therefore, human beings have to seek other sources of power to generate high levels of power while using the available resources in a sustainable manner. For example, most hydropower stations need large tracks of land and a lot of water to produce (Alexandra, 2006). This raises the need to build large dams to hold the required water and construct power stations that will generate the required power. With land becoming a scarce resource, hydroelectric power generation is becoming more expensive to produce. This consequently raises the need for other energy sources to satisfy the ever-growing power demand.  Nuclear power has promised to satisfy this need. Nuclear energy production utilizes uranium to produce energy. Uranium, which was discovered in the 18th century by Martin Klaproth is found everywhere on earth (Alexandra, 2006). In most cases, this element is found in trace quantities. However, this heavy metal is an abundant source of concentrated energy meaning that it can be used in small quantities to produce a large amount of power. This paper will analyze this element for its strengths, weaknesses, opportunities and threats in nuclear power generation.

Strengths

One of the major strengths of uranium is that it occurs in three isotopes, which include uranium 234, uranium 235 and uranium 238. The uranium 238 isotope is the most prevalent in the world and has a half-life of about 4.5 billion years. The high availability of uranium means that its cost is considerably lo and this consequently lowers the cost of producing nuclear power. Furthermore, the use of uranium does not emit any greenhouse gases into the environment (Beli͡aev, 2012). With the effects of greenhouse gases being felt in the environment, governments and other relevant authorities have been placing emphasis on the use of environmentally friendly power sources. The emission of greenhouse gases from reactors that use uranium as a major fuel are negligible and this means that uranium is a perfect material for energy production in today’s world (Beli͡aev, 2012).

In addition to this, compared to other power sources such as fossil fuels, uranium is less prone to fuel price increases. This means that the cost of uranium is highly stable which means that producers can stick to budget estimates and ensure that they produce sufficient energy supply. Energy producers who use other sources of fuel such as fossil fuels are always facing the risk of high fuel costs, which may reduce their power production reliability. This is not the case with uranium, whose prices remains considerably stable. For example, the highest uranium prices were experienced in the year 2007 with prices peaking at one hundred and thirty five dollars per pound. Since that period, the prices have been on a constant drop with one pound costing forty dollars by the end of 2015 (uxc.com, 2016). This shows that uranium is a considerably cheap source of power. Additionally, uranium has a high energy density, which means that it can be stored and used in small quantities as compared to other fuels. This further reduces the cost of producing nuclear energy from uranium and increases the efficiency with which this energy is produced. Furthermore, the waste generated by uranium after generation of power is considerably small which means that this waste is highly manageable. This consequently reduces the environmental impact of using uranium in the production of nuclear power (Beli͡aev, 2012).

Weaknesses

One of the major weaknesses of uranium in the production of nuclear energy is the fact that this element is highly unstable. Therefore, any incident or accident involving this material would be very devastating on the environment and its habitats. For example, accidents involving this material like Chernobyl have rendered these areas uninhabitable for human beings and other living things (Azapagic & Perdan, 2011). In addition to this, setting up reactors that use uranium to generate power is a capital-intensive activity. Building and running these reactors may use a lot of financial resources which means that uranium cannot be used by countries which are financially unstable. In addition to these, developers of repositories for High Activity Waste have been slow and this means that the available uranium waste management platforms may be inadequate (Azapagic & Perdan, 2011). Furthermore, compared to renewable energy sources such as wind and solar, uranium resources are considerably limited. Finally, public perceptions and acceptance of nuclear energy is a major element for volatility, which reduces the use of uranium as a source of fuel.

Opportunities

As seen earlier, the need for new and more power generation capacities is one of the major drivers of uranium for power generation. Uranium has a very high capacity for power generation and this one of the major opportunities for uranium (Chatterjee, 2006). Secondly, the world is moving towards the elimination of the conventional carbon-emitting power generators and plants. This provides a major opportunity for the usage of uranium because nuclear power plants do not have any carbon or greenhouse gas emissions (Chatterjee, 2006). In addition to this, as the costs and prices of fossil fuels continue to increase, governments and relevant authorities are pushing for the adoption of cheaper fuels. This means that uranium has a high chance of becoming the next major source of energy in the world. Further, new technologies such as Generation IV nuclear power reactors promise high levels of material utilization efficiency as well as waste reduction capabilities (Chatterjee, 2006). This means that uranium can be used without the worry of waste management and disposal. Finally, researchers have been focusing their efforts on the fuel cycle in a bid to reduce the radiotoxicity of uranium waste as well as reducing the level of wastes. This means that new technologies will eliminate radiotoxic materials in uranium waste and thereby provide more opportunities for its usage (Chatterjee, 2006).

Threats

One of the major threats in the usage of uranium as a major fuel is the increasing risk of terrorist threats on nuclear infrastructure. As the threat of terrorism becomes a reality in today’s world, terrorists are targeting non-conventional targets in a bid to increase casualties (Alexandra, 2006). As seen earlier, any incident or accident involving uranium can be very devastating and this poses a major threat to the adoption of uranium as a power source. Secondly, industry capacities and sources of skilled labor pose major bottlenecks in the expansion of nuclear energy production. This poses another major threat to the adoption of uranium in the production of nuclear energy as it creates technology-specific jobs, which need highly qualified professionals (Alexandra, 2006). In addition, as seen earlier, High Activity Waste management repositories have not been fully developed and the current management systems are inadequate. This further poses a major threat to the adoption of uranium, which produces high activity waste materials. Additionally, as the world moves towards sustainability, solar and wind energy has received more focus and attention of researchers. These energy sources are considered stronger contenders for sustainable development than uranium. Finally, changes in nuclear accident liabilities are threatening to change the course of power generation. As producers are considered more liable in accidents, they might shy away from investing their resources in nuclear power generation and thereby reduce the chances of uranium being adopted as a major fuel (Alexandra, 2006).

Solutions

As seen above, uranium provides major solutions to the problem of power production capacity, greenhouse gas emissions, high costs of energy production and the constantly increasing power prices. Furthermore, the use of uranium promises lower energy prices thereby benefiting the end consumer. In addition, the lower production costs have a direct bearing on the reliability of power production and supply. This means that uranium is a viable solution to the problems that have been experienced in today’s world. With proper technologies and technical support, nuclear energy is more viable than other power sources such as hydroelectric and fossil fuel power stations. This means that if governments and other relevant authorities would be able to overcome the major challenges facing the adoption of uranium in the production of nuclear energy, the world would be able to enjoy the benefits of reliable and adequate power supply from uranium.

Conclusion

Radioactivity is the major limitation to the adoption of uranium as a major fuel today. However, with proper management techniques and technologies, uranium is one of the best fuel currently available in the world. The element is less prone to fuel price fluctuations and its high energy density means that it can be used in small quantities to produce large amounts of power. Additionally, it solves the problems of greenhouse gas emissions and thereby promotes sustainable development. However, with high set up costs and threats of terrorism, uranium is bound to take longer before it is adopted as a major fuel in the world.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

References

Alexandra, C. M. (Ed.). (2006). Depleted uranium: properties, uses, and health consequences. CRC Press.

Azapagic,A., & Perdan, S., (2011). Sustainable development in practice: Case studies for engineers and scientists. Hoboken, N.J: Wiley.

Beli͡aev, L. S. (2012). World Energy and Transitions to Sustainable Development. Springer Science & Business Media.

Chatterjee, K. K. (2006). Uses of energy minerals and changing techniques. New Delhi: New Age International (P) Ltd. Publishers.

uxc.com,. (2016). Ux U3O8 Price – Full History. UxC Historical Ux Price Charts. Retrieved 23 April 2016, from https://www.uxc.com/p/prices/UxCPriceChart.aspx?chart=spot-u3o8-full

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