Question

Assertion :The volume of 0.1M ${KMnO}_4$ required to oxidise 20 ml of 0.1 M oxalic acid in acidic medium is 20 ml. Reason: 2 moles of ${KMnO}_4$ = 5 moles of oxalic acid in acidic medium reaction.

• A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
• B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
• C. Assertion is correct but Reason is incorrect
• D. Assertion is incorrect but Reason is correct

Answer 1

The correct option is D Assertion is incorrect but Reason is correct

$2{{MnO}_4}^{-}+16H^{+}+5{C_2{O}_4}^{2-}\to 2{Mn}^{+2}+8H_{2}O+10C{O}_2$.

Assertion: $N_1{V}_1=N_2{V}_2$

$V_1=\frac{N_2{V}_2}{N_1}=\frac{0.1\times 20}{(0.1\times 5)}=4mL$

Hence, an assertion is wrong. the volume requires is 4 mL and not 20 mL. Please note, valency factor of oxalic acid is +1 (as the oxidation number of carbon changes from +3 to +4) and the valency factor of potassium permanganate is 5 (as oxidation number of $Mn$ changes from +7 to +2).

Reason: From the above-balanced chemical reaction, it gets clear that 2 moles of ${KMnO}_4$ react with 5 moles of oxalic acid. Hence, the reason is true.

Hence, D is the correct answer.