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Question

0.3g of an oxalate was dissolved in 100 mL solution. The solution required 90 mL of N20 KMnO4 for complete oxidation. The % of oxalate ion in salt is:

A
33%
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B
66%
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C
70%
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D
40%
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Solution

The correct option is D 66%
The reaction taking place between manganate and oxalate is as follows:

2MnO4+5C2O24+16H+2Mn2++5CO2+8H2O

Mn changes from +7 to +2 after oxidizing oxalate. Net change in oxidation state =5

C in oxalate changes from +3 to +4 after being oxidized. Net change in oxidation state =2×1=2

Hence, 1 equivalent of KMnO4 oxidizes 2.5 equivalences of oxalate.

According to the given data,
Moles of KMnO4=0.05×0.095=9×104

Moles of oxalate that KMnO4 oxidizes =9×104×2.5==2.25×103

Molecular weight of oxalate (C2O4): 2×12+4×16=88

Oxalate ion amount =2.25×103×88==0.198

Percentage of oxalate ion =0.198×1000.3=66%

Hence, the correct option is B

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