a) Explain in bullet points how to prepare the dilution series. c) Calculate the
ID: 913672 • Letter: A
Question
a) Explain in bullet points how to prepare the dilution series.
c) Calculate the mass % of copper in the alloy.
d) If the cuvette used to measure the dissolved sample had finger smudges, how would the calculated mass % of copper be affected? Explain
f) Describe another lab technique that could be used to determine the mass % of Ag in the sample.
g) H+ + Ag(s) + HNO3 --> Ag+1 + NO2 + H2O ;
2H+ + Cu(s) + 2HNO3 --> Cu+2 + 2NO2 + 2H2O
The 2 equations are for the dissolution of Ag and Cu. What assumption could the student make about the sample to insure that excess 16 M HNO3 is used to dissolve the alloy sample?
Explanation / Answer
a) To prepare dilution series starting with 0.1 M Cu(NO3)2
For 100 ml of 0.02 M solution,
M1V1 = M2V2
0.1 x V1 = 0.02 x 100
volume of 0.1 M solution taken V1 = 20 ml and diluted to 100 ml
For 100 ml of 0.04 M solution,
M1V1 = M2V2
0.1 x V1 = 0.04 x 100
volume of 0.1 M solution taken V1 = 40 ml and diluted to 100 ml
For 100 ml of 0.06 M solution,
M1V1 = M2V2
0.1 x V1 = 0.06 x 100
volume of 0.1 M solution taken V1 = 60 ml and diluted to 100 ml
For 100 ml of 0.08 M solution,
M1V1 = M2V2
0.1 x V1 = 0.08 x 100
volume of 0.1 M solution taken V1 = 80 ml and diluted to 100 ml
c) mass% of Cu in the alloy
A1/A2 = C1/C2
0.16/0.23 = 0.02/x
x = 0.029
mass % of Cu in sample = 2.87 %
d) If the cuvetter had finger smudges, the mass % of copper would be lower than actual values.
f) Ag in the sample can be determines by precipitation as AgCl.
AgNO3 + Cl- ---> AgCl + NO3-
The assumptions a student has to mkae is that the alloy only consists of Ag and Cu and all of it reacts with HNO3.
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.