A 0.4676 g sample of pewter, containing tin, lead, copper, and zinc, was dissolv
ID: 957909 • Letter: A
Question
A 0.4676 g sample of pewter, containing tin, lead, copper, and zinc, was dissolved in acid. Tin was precipitated as.SnO_2 4H_2O and removed by filtration. The resulting filtrate and washings were diluted to a total volume of 300.0 mL, A 20.00 mL aliquot of this solution was buffered, and titration of the lead, copper, and zinc in solution required 34 68 mL of 0.001468 M EDTA. Thiosulfate was used to mask the copper in a second 25 00 mL aliquot. Titration of the lead and zinc in this ahquot required 33.97 mL of the EDTA solution. Finally, cyandlde was use to mask the copper and the zinc in a third 30.00 mL aliquot. Titration of the lead in this aliquol required 25.79 mL of the EDTA solution. Determine the percent composition by mass of each metal in the poewner sample.Explanation / Answer
Data.
0.4676 g sample of (Pb, Cu, Zn, Sn)
Total Volume = 300 ml = 0.3 L
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Start with lead titration:
Total moles of EDTA used for Pb, Cu, Zn = 0.001468 M x 34.68 ml = 0.0509 mmol in 20 ml aliquot
moles of Pb,Cu, Zn in 300 ml solution = 0.7636 mmol
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Total EDTA used for Pb, Zn = 0.001468 M x 33.97 ml = 0.049 mmol in 25 ml aliquot
moles of Pb, Zn in 300 ml solution = 0.5984 mmol
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Total EDTA used for Pb = 0.001468 M x 25.79 ml = 0.0378 mmol in 30ml aliquot
moles of Pb present in 300 ml solution = 0.3786 mmol
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moles of Cu present = 0.7636 mmol(Pb,Cu,Zn) - 0.5984 mmol(Pb,Zn) = 0.1652 mmol (Cu)
mass of Cu present = 0.1652 mmol (Cu) x (63.55 g/mol)/1000 = 0.0105 g (Cu)
mass% Cu in sample = (0.0105g/0.4676g) x 100 = 2.25 %
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mass of Pb present in sample = 0.3786 mmol (Pb) x (207.2 g/mol)/1000 = 0.078 g (Pb)
mass% of Pb in sample = (0.078g/0.4676g) x 100 = 16.77%
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moles of Zn present in sample = 0.5984 mmol (Pb, Zn) - 0.3786 mmol (Pb) = 0.2198 mmol (Zn)
mass of Zn present in sample = 0.2198 mmol (Zn) x (65.39 g/mol)/1000 = 0.0144 g (Zn)
mass% of Zn in sample = (0.0144g/0.4676g) x 100 = 3.07%
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mass of Sn in sample = 0.4676g sample - [0.0105 g (Cu) + 0.078 g (Pb) + 0.0144 g (Zn)] = 0.3647 g (Sn)
mass% of Sn in sample = (0.3647g/0.4676g) x 100 = 77.91%
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Table.
% Pb = 16.77%
% Cu = 2.25%
% Zn = 3.07%
% Sn = 77.91%
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Total: 100%
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