Assertion : Amount of H_2O_2 in a sample can | vedclass

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Question

(B) The Assertion is true because $H_2O_2$ reacts with $KI$ in acidic medium to liberate $I_2$: $H_2O_2 + 2KI + 2H^+ \rightarrow 2K^+ + 2H_2O + I_2$.

Vedclass · Accepted Answer

Assertion and Reason both are correct but Reason is not the correct explanation of Assertion.

Vedclass · Answer

(B) The Assertion is true because $H_2O_2$ reacts with $KI$ in acidic medium to liberate $I_2$: $H_2O_2 + 2KI + 2H^+ \rightarrow 2K^+ + 2H_2O + I_2$. The liberated $I_2$ is then titrated against sodium thiosulphate $(Na_2S_2O_3)$: $I_2 + 2Na_2S_2O_3 \rightarrow 2NaI + Na_2S_4O_6$. The Reason is also true because starch is used as an indicator in this iodometric titration. Starch forms an intense blue-black complex with $I_2$,which disappears when all $I_2$ is consumed by thiosulphate at the end point. However,the appearance of the blue colour is a property of the indicator used,not the reason why the amount of $H_2O_2$ can be determined. Therefore,the Reason is not the correct explanation of the Assertion.

Assertion $:$ Amount of $H_2O_2$ in a sample can be determined by treating $H_2O_2$ solution with $KI$ and followed by titration of liberated $I_2$ with sodium thiosulphate.
Reason $:$ In this titration,an intense blue colour appears which disappears at the end point.

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Assertion $:$ Amount of $H_2O_2$ in a sample can be determined by treating $H_2O_2$ solution with $KI$ and followed by titration of liberated $I_2$ with sodium thiosulphate. Reason $:$ In this titration,an intense blue colour appears which disappears at the end point.