A sample containing only Na2C2O4 and KHC2O4 required three times the volume of 0.1NKMnO4 for titration as compared to that of 0.1N base (same size sample in each case). Percentage of KHC2O4 in the mixture is:
A
65.64%
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B
34.36%
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C
30.28%
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D
69.72%
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Solution
The correct option is A65.64% The dissociation equations are as shown below: Na2C2O4→2Na++C2O42− KHC2O4→K++H+C2O42− Let x moles of Na2C2O4 and y moles of KHC2O4 be present. Therefore, (x+y) moles of C2O42− ions are present. This corresponds to 2(x+y) equivalents. y moles of hydrogen ions are present. This corresponds to y equivalents. Let V ml be the volume of 0.1N base required. 0.1×V1000=y
V=10000y
The volume of 0.1NKMnO4 is 3V.
∴0.1×3V1000=2(x+y)
0.1×3×10000y1000=2(x+y)
3y=2x+2y
y=2x
The amount of Na2C2O4=134x g The amount of KHC2O4=y mol =2x mol =2×128x g =256x g The percentage of KHC2O4 in the mixture is 256x256x+134x×100=65.64%