Part A. Preparation of Saturated Solutions of Cadmium Oxalate 1. You need to prepare three saturated solutions of CdC,o. Clearly label three small beakers 1, 2, and 3. 2. Clean and properly rinse your buret (Laboratory Methods B2). Obtain 50 mL of 0.100 M cadmium nitrate, Cd(NO,),, from the reagent shelf. Rinse your buret with a very small por- tion of this solution, then fill the buret with the Cd(NO,),. 3. To Beaker 1 add 200 mL of distilled water and 25.00 mL of Cd(NO,),solution. 4. To Beakers 2 and 3 add 10.00 mL portions of Cd(NO,), solution from the buret.

Appl Of Ms Excel In Analytical Chemistry
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Chapter10: Potentiometry And Redox Titrations
Section: Chapter Questions
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How many total mL of 0.100 M Cd(NO3)2 will you need to take from the reagent shelf in order to prepare the solutions in Beakers 1 plus 2 plus 3? Justify your answer by showing how you will use this total volume of solution.

 

12. Titration of the samples:
At this point in your chemistry lab course, you should be very comfortable with the
titration procedure, so the instructions will be kept brief.
Clean and rinse your buret. Obtain no more than 40 mL of approximately 0.01 M potas-
sium permanganate, KMNO,, from the
volume of KMno, then fill your buret with the solution.
a.
reagent
shelf. Rinse
your
buret with a very small
4
4'
b. Record in Table 19.1B the KMNO, molarity shown on the bottle. (Since KMNO, is a dark
purple solution, it can be difficult to read the volume markings on the buret. To make this
easier, you should read the TOP of the meniscus, rather than the bottom, throughout this
titration.)
c. Heat one 100 mL portion of the filtrate to 55°C-60°C. Temperature control is critical in
this experiment. At temperatures below 55°C, the reaction is too slow, and above 60°C
oxalic acid decomposes. Titrate the hot solution with the KMNO, solution. The endpoint
will be the point in the titration at which the pink color of KMNO, first persists for about
30 seconds. Record your titration data in Table 19.1B, taking care to read the volumes to
the nearest hundredth of a milliliter.
d. Repeat the titration with the second 100 mL portion of CdC,O, solution, and record your
data in Table 19.1B.
Part C. Determination of the Equilibrium Constant for the
Formation of [Cd(NH,),+]
4
13. Clean and rinse your buret. Obtain no more than 40 mL of approximately 5 M aqueous am-
monia, NH,. Record in Table 19.1C the molarity of the NH, shown on the bottle. Rinse the
buret with a very small volume of NH, solution, then fill the buret with NH,.
14. Titrate the mixture in Beaker 2. The endpoint will be the point at which the solid CdC,0,
completely disappears. In order to determine this endpoint easily, put a dark cross on a piece
of white paper that is placed under the beaker of mixture you are titrating. When all solid
CdC,O, is gone, you will be able to see the cross clearly. Record your titration data in Table
19.1C.
15. Repeat the titration of the mixture in Beaker 3, and record your data in Table 19.1C.
16. After the experiment is complete, clean your buret with about 2-5 mL of hydrogen peroxide
before returning the buret to the Stockroom.
17. Dispose of all wastes in the proper waste containers on the reagent shelf.
Before the next lab, perform the calculations in Table 19.2 including sample calculations for one
run following Table 19.2.
Transcribed Image Text:12. Titration of the samples: At this point in your chemistry lab course, you should be very comfortable with the titration procedure, so the instructions will be kept brief. Clean and rinse your buret. Obtain no more than 40 mL of approximately 0.01 M potas- sium permanganate, KMNO,, from the volume of KMno, then fill your buret with the solution. a. reagent shelf. Rinse your buret with a very small 4 4' b. Record in Table 19.1B the KMNO, molarity shown on the bottle. (Since KMNO, is a dark purple solution, it can be difficult to read the volume markings on the buret. To make this easier, you should read the TOP of the meniscus, rather than the bottom, throughout this titration.) c. Heat one 100 mL portion of the filtrate to 55°C-60°C. Temperature control is critical in this experiment. At temperatures below 55°C, the reaction is too slow, and above 60°C oxalic acid decomposes. Titrate the hot solution with the KMNO, solution. The endpoint will be the point in the titration at which the pink color of KMNO, first persists for about 30 seconds. Record your titration data in Table 19.1B, taking care to read the volumes to the nearest hundredth of a milliliter. d. Repeat the titration with the second 100 mL portion of CdC,O, solution, and record your data in Table 19.1B. Part C. Determination of the Equilibrium Constant for the Formation of [Cd(NH,),+] 4 13. Clean and rinse your buret. Obtain no more than 40 mL of approximately 5 M aqueous am- monia, NH,. Record in Table 19.1C the molarity of the NH, shown on the bottle. Rinse the buret with a very small volume of NH, solution, then fill the buret with NH,. 14. Titrate the mixture in Beaker 2. The endpoint will be the point at which the solid CdC,0, completely disappears. In order to determine this endpoint easily, put a dark cross on a piece of white paper that is placed under the beaker of mixture you are titrating. When all solid CdC,O, is gone, you will be able to see the cross clearly. Record your titration data in Table 19.1C. 15. Repeat the titration of the mixture in Beaker 3, and record your data in Table 19.1C. 16. After the experiment is complete, clean your buret with about 2-5 mL of hydrogen peroxide before returning the buret to the Stockroom. 17. Dispose of all wastes in the proper waste containers on the reagent shelf. Before the next lab, perform the calculations in Table 19.2 including sample calculations for one run following Table 19.2.
Experimental Procedure
Study this section and the Pre-Laboratory Questions before coming to the laboratory.
Wear safety goggles when performing this experiment.
Part A. Preparation of Saturated Solutions of Cadmium
Oxalate
1. You need to prepare three saturated solutions of CdC,0. Clearly label three small beakers 1,
2, and 3.
2. Clean and properly rinse your buret (Laboratory Methods B2). Obtain 50 mL of 0.100 M
cadmium nitrate, Cd(NO,),, from the reagent shelf. Rinse your buret with a very small por-
tion of this solution, then fill the buret with the Cd(NO,),.
3. To Beaker 1 add 200 mL of distilled water and 25.00 mL of Cd(NO,), solution.
4. To Beakers 2 and 3 add 10.00 mL portions of Cd(NO,), solution from the buret.
5. Clean your buret again, and fill it this time with 0.100 M sodium oxalate, Na,C,O, solution.
6. Add 25.00 mL of this Na,C,O, solution to Beaker 1, and 10.00 mL each to Beakers 2 and 3.
Stir the mixtures for at least 10 minutes each to allow the particle size to grow, and then permit
the precipitates to settle. **You may be tempted to skip the stirring step. DON'T. Failure to
sufficiently stir the solutions will result.
7. Beaker 1 will be used for Part B; Beakers 2 and 3 will be used for Part C.
Part B. Determination of the Solubility Product of CdC,0,
8. Using gravity filtration (Laboratory Methods H1), filter the mixture in Beaker 1.
9. You will be using your buret to precisely add 200 mL of filtrate to each of two Erlenmeyer
flasks. Clean your buret, and rinse it with a few milliliters of the filtrate. (Do not waste filtrate!)
Fill the buret with the filtrate, and carefully adjust the volume to the zero-mark.
10. Using your buret, measure 100 mL of filtrate into each of two Erlenmeyer flasks. (You will
need to fill your buret twice in order to measure the required 100 mL of filtrate for each of the
two flasks.)
11. Add 20 mL of 3 M sulfuric acid, H,SO, solution to each flask.
CAUTION: Dilute H,So, is corrosive and causes burns on your skin or holes in your
clothing. If there are any spills or spatters onto your skin or clothing, rinse the affected
area thoroughly with water.
Transcribed Image Text:Experimental Procedure Study this section and the Pre-Laboratory Questions before coming to the laboratory. Wear safety goggles when performing this experiment. Part A. Preparation of Saturated Solutions of Cadmium Oxalate 1. You need to prepare three saturated solutions of CdC,0. Clearly label three small beakers 1, 2, and 3. 2. Clean and properly rinse your buret (Laboratory Methods B2). Obtain 50 mL of 0.100 M cadmium nitrate, Cd(NO,),, from the reagent shelf. Rinse your buret with a very small por- tion of this solution, then fill the buret with the Cd(NO,),. 3. To Beaker 1 add 200 mL of distilled water and 25.00 mL of Cd(NO,), solution. 4. To Beakers 2 and 3 add 10.00 mL portions of Cd(NO,), solution from the buret. 5. Clean your buret again, and fill it this time with 0.100 M sodium oxalate, Na,C,O, solution. 6. Add 25.00 mL of this Na,C,O, solution to Beaker 1, and 10.00 mL each to Beakers 2 and 3. Stir the mixtures for at least 10 minutes each to allow the particle size to grow, and then permit the precipitates to settle. **You may be tempted to skip the stirring step. DON'T. Failure to sufficiently stir the solutions will result. 7. Beaker 1 will be used for Part B; Beakers 2 and 3 will be used for Part C. Part B. Determination of the Solubility Product of CdC,0, 8. Using gravity filtration (Laboratory Methods H1), filter the mixture in Beaker 1. 9. You will be using your buret to precisely add 200 mL of filtrate to each of two Erlenmeyer flasks. Clean your buret, and rinse it with a few milliliters of the filtrate. (Do not waste filtrate!) Fill the buret with the filtrate, and carefully adjust the volume to the zero-mark. 10. Using your buret, measure 100 mL of filtrate into each of two Erlenmeyer flasks. (You will need to fill your buret twice in order to measure the required 100 mL of filtrate for each of the two flasks.) 11. Add 20 mL of 3 M sulfuric acid, H,SO, solution to each flask. CAUTION: Dilute H,So, is corrosive and causes burns on your skin or holes in your clothing. If there are any spills or spatters onto your skin or clothing, rinse the affected area thoroughly with water.
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