A 3.4 g sample of H2O2 solution containing x% by mass requires x ml of a KMnO4 solution for complete oxidation under acidic medium. The molarity of KMnO4 solution is:
A
1.0 M
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B
0.5 M
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C
0.4 M
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D
0.2 M
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Solution
The correct option is C 0.4 M Reaction of H2O2 with KMnO4 is as 5H2O2+2KMnO4+6H+→2K++2Mn2++8H2O+5O2 Now 100 gm of H2O2 soln. contains x gm H2O2 So 3.4 gm of soln. will have (x100)∗3.4 mass of H2O2 wiil be (x100)∗3.4 gm The number of moles of H2O2 will be n1=givenmassmolecularmass ` = 0.001x` Similarly moles of KMnO4 will be: n2 =Normality∗volume (in litres) =M×x1000 Now H2O2 and KMnO4 react in the ratio of 5:2 so n15=n22 0.001x5=0.001Mx2 giving Molarity = 0.4 M