NOTE: A preparation scheme for the following solutions should be made up in your
ID: 844833 • Letter: N
Question
NOTE: A preparation scheme for the following solutions should be made up in your lab book before coming to the lab. Your instructor may ask to see it before you start the lab. 1. Prepare intermediate 0.00500 M stock solutions of CuCl2, CdCl2, Pb(NO3)2, and NBA in 100.0 mL volumetric flasks using the 0.100 M stock solutions provided. 2. Using the intermediate stock solutions and the 2.5 M acetic acid buffer, prepare the following solutions in 25.00 mL volumetric flasks: a. 1 M (1:1) acetic acid buffer b. 2.00 x 10^-4 M Cu2+ in 1 M (1:1) acetic acid buffer c. 2.00 x 10^-4 M Cd2+ in 1 M (1:1) acetic acid buffer d. 2.00 x 10^-4 M Pb2+ in 1 M (1:1) acetic acid buffer e. 4.00 x 10^-4 M Pb2+ in 1 M (1:1) acetic acid buffer f. 6.00 x 10^-4 M Pb2+ in 1 M (1:1) acetic acid buffer g. 2.00 x 10^- 4 M NBA in 1 M (1:1) acetic acid buffer h. unknown mixture in 1 M (1:1) acetic acid bufferExplanation / Answer
1. Since the stock solutions are of strength 0.1 M , and we want intermediate stock solutions of 0.005 M concentrations, this means we have to dilute it 20 times. We have 100 ml flasks, we do the following for each of the compound:
Take 5 ml of the 0.1 M stock solution and add 95 ml distilled water to it. This way, it gets diluted 20 times !
Do this for all the four compounds separately.
2. Given strength of acetic acid buffer = 0.250 M , Volume of flask used = 25 ml
a) Mix 10 ml of 0.25 M acetic acid buffer and 15 ml distilled water
b) Mix 1 ml of intermediate stock solution of CuCl2 with 24 ml 1M acetic acid buffer, that is, the one we prepared in part 2(a)
c) Mix 1 ml of intermediate stock solution of CdCl2 with 24 ml 1M acetic acid buffer
d) Mix 1 ml of intermediate stock solution of Pb(NO3)2 with 24 ml 1M acetic acid buffer
e) Mix 2 ml of intermediate stock solution of Pb(NO3)2 with 23 ml 1M acetic acid buffer
f) Mix 3ml of intermediate stock solution of Pb(NO3)2 with 22 ml 1M acetic acid buffer
g) Mix 1 ml of intermediate stock solution of NBA with 24 ml 1M acetic acid buffer
h) Mix 'x' ml of intermediate stock solution of any of the 4 compounds with (25-x) ml 1M acetic acid buffer
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