Analytical Chemistry @CSU Stanislaus

CHEM 2012 Quantitative Analysis Laboratory

Laboratory Safety
The usual rules will apply. These include:

  1. No smoking, eating or drinking allowed in the lab.
  2. No unauthorized experiments or removal of chemicals.
  3. Safety goggles are required at all times and are available at the bookstore. Contact lenses or eye glasses are not adequate eye protection. Contact lenses can be dangerous and their use should be avoided if at all possible.
  4. Consult the Material Data Safety Sheets (MSDS) before using a chemical. These are available from the Chemistry Stockroom web page.

Please read Chapter 35, especially sections A, B, D, E, J and K, before starting to work in the laboratory.

You will be given the unknowns at the beginning of the semester. Record the code number for each unknown directly in your notebook along with the approximate analysis value if it is given.

The specific notes below take precedence over the text where they differ.

Approximate CHEM 2012 Lab Schedule For Fall 2001
Date / References Experiments
Sep 6
FAC
Chap. 35 A, B, D, E, G, J, K
Chap. 36 A-1
  • Check-in
  • Prepare Desiccators
  • The Electronic Balance
  • Gravimetric Determination of a Soluble Chloride
Notes: Use the sample labeled "Soluble Chloride". There is enough for 4 trials. A solution of 0.2 M AgNO3 is provided. Use the approximate percent to calculate the minimum amount of AgNO3 solution to add to each sample.
Sep 18

FAC
Chap. 6 A, B, C
Chap. 10 A, B, C
Chap. 12 A
Chap. 35 H, I
Chap. 36 B-4,B-7, B-8

  • Calibrate Buret

  • Prepare and Standardize Sodium Hydroxide Solution

  • Determination of Potassium Hydrogen Phthalate KHP) in an Impure Sample

Notes: Use the sample labeled "KHP Unk". There is enough for 4 trials. Calculate your sample size assuming that the sample is 50% KHP and plan to use about 40 mL of your NaOH solution.

Sep 25

FAC
Chap. 14
Chap. 36 D-2, D-3

  • Preparation of Standard EDTA Solution

  • Determination of Magnesium by Direct Titration

Notes: Although the EDTA is a primary standard, it is only 99.7% pure. Use the sample labeled "Mg Titration Unk" and do not dry it. You must dissolve all of the sample in water and dilute to 500.00 mL in a volumetric flask because the sample is heterogeneous. Use a 50.00 mL pipet to remove an aliquot for each trial. For an indicator, use Calmagite instead of Eriochrome Black T. It will display the same color change but it is more stable.

Oct 9

FAC
Chap. 13
Chap. 36 I-1, I-2

  • Preparation of Standard Silver Nitrate Solution

  • Potentiometric Titration of Chloride and Iodide in a Mixture

Notes: Use the sample labeled "I-Cl Unk" and do not dry it. All of the sample must be dissolved in a 250.00 mL volumetric flask. Use a 50.00 mL aliquot for each sample. Use the solid AgNO3 provided with the samples to prepare your standard solution. It is easiest to use a glass electrode as described in the text. The titration curve will show 2 end points. Do not stop until you have gone past both. It is most efficient and accurate to add large amounts of titrant before and after each end point and successively smaller amounts as you encounter the steeper regions of your curve. In the steepest part you should be adding only 1 drop between measurements.

Oct 23

FAC
Chap. 24 A-4
Chap. 36 M-4

  • Spectrophotometric Determination of pH

Notes: Bring an empty and clean 250 mL Erlenmeyer flask to the Stockroom and  for your sample. Measure the pH of 3 or 4 aliquots of this solution spectrophotometrically, as described in your text.

Nov 1

FAC
Chap. 4E
Chap. 28
Chap. 36 Q-1

Attached Handout

  • Determination of Ethanol in Beer by Gas Chromatography

Notes: The beer samples are available from the Stockroom. Be certain to record the brand and other information from the label. They are warm so open the sample carefully. The carbonation can be removed by stirring and then filtering through filter paper. Use the internal standard method and plot the area ratios for the standards vs. the volume of standard propanol. Determine the slope and intercept of the best line through your data points. Also determine the standard deviation of the slope and intercept. Use this information to calculate the concentration of the beer in the diluted unknown and the uncertainty of the result. Do at least 3 sets of injections. There is only one GC for this experiment so plan your time accordingly.  Report the %-ethanol in the undiluted beer sample.

Nov 13

FAC
Chap. 12
Chap. 36 I-3

  • Potentiometric Determination of Solute Species in a Carbonate Mixture

Notes: Use the sample labeled "Carbonate Mix Unk". Dissolve the entire sample and dilute to 250.00 mL in a volumetric flask. Use 50.00 mL aliquots for each trial. Measure the pH to determine the sample composition and the method of analysis. Prepare and standardize HCl and/or NaOH solutions as appropriate. Obtain a titration curve potentiometrically and choose the best indicator(s). Finally, titrate the remaining samples to the indicator endpoints.

Nov 27

FAC
Chap. 4 E
Chap. 24
Chap. 36 M-3

  • Determination of Manganese in Steel

  • Checkout

Notes: Use the sample labeled "Steel Unk". Calculate the sample size based on the approximate percent of manganese. Prepare a series of standard addition solutions with volumes of 1.00, 2.00, 3.00, 4.00 and 5.00 mL of standard Mn solution. Plot the absorbance of the solutions vs. the amount of Mn added to determine the concentration of manganese in the aliquot to which no Mn has been added. Analyze your plot as in the GC experiment. From this result calculate the percent of Mn in the original sample.


Note: After completing all eight experiments, you may repeat any experiment you wish in order to earn a higher score.  The new score will replace the original score for the repeated experiment.

comments to:
jim byrd
chair, department of chemistry
california state university, stanislaus
jim@chem.csustan.edu

Copyright © 2001