JEE Main 2022 — Chemistry Physical Chemistry

2022integerhard

$20\mathrm{mL}$ of $0.02M$ hypo solution is used for the titration of $10\mathrm{mL}$ of copper sulphate solution, in the presence of excess of $\mathrm{KI}$ using starch as an indicator. The molarity of ${\mathrm{Cu}}^{2+}$ is found to be $_____\times {10}^{-2}M$ (nearest integer)

Given : $2{\mathrm{Cu}}^{2+}+4{I}^{-}\rightarrow {\mathrm{Cu}}_{2}{I}_{2}+{I}_{2} {I}_{2}+2{S}_{2}{O}_{3}^{-2}\rightarrow 2{I}^{—}+{S}_{4}{O}_{6}^{-2}$

Official previous-year question

Held on 26 Jul 2022 · Verified 6 Jul 2026.

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Solution

${n}_{\mathrm{eq}.}$ of ${I}_{2}={n}_{\mathrm{eq}}$ of ${\mathrm{Na}}_{2}{S}_{2}{O}_{3}=20\times 0.02\times {10}^{-3}$

$2\times {n}_{\mathrm{mol}}$ of ${I}_{2}=0.4\times {10}^{-3}$

${n}_{\mathrm{mol}}$ of ${I}_{2}=0.2m\mathrm{mol}$

${n}_{\mathrm{mol}}$ of ${\mathrm{Cu}}^{+2}=0.2\times 2\times {10}^{-3}$

$[{\mathrm{Cu}}^{+2}]=\frac{0.4\times {10}^{-3}}{10\times {10}^{-3}}=0.04=4\times {10}^{-2}$

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JEE Main 2022 — Chemistry Physical Chemistry

2022integerhard

Given : $2{\mathrm{Cu}}^{2+}+4{I}^{-}\rightarrow {\mathrm{Cu}}_{2}{I}_{2}+{I}_{2} {I}_{2}+2{S}_{2}{O}_{3}^{-2}\rightarrow 2{I}^{—}+{S}_{4}{O}_{6}^{-2}$

Official previous-year question

Held on 26 Jul 2022 · Verified 6 Jul 2026.

Did you get this right?

Solution

${n}_{\mathrm{eq}.}$ of ${I}_{2}={n}_{\mathrm{eq}}$ of ${\mathrm{Na}}_{2}{S}_{2}{O}_{3}=20\times 0.02\times {10}^{-3}$

$2\times {n}_{\mathrm{mol}}$ of ${I}_{2}=0.4\times {10}^{-3}$

${n}_{\mathrm{mol}}$ of ${I}_{2}=0.2m\mathrm{mol}$

${n}_{\mathrm{mol}}$ of ${\mathrm{Cu}}^{+2}=0.2\times 2\times {10}^{-3}$

$[{\mathrm{Cu}}^{+2}]=\frac{0.4\times {10}^{-3}}{10\times {10}^{-3}}=0.04=4\times {10}^{-2}$

JEE Main 2022 — Chemistry Physical Chemistry

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JEE Main 2022 — Chemistry Physical Chemistry

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Solution

Your note

JEE Main Physical Chemistry in other years

More JEE Main Physical Chemistry questions

Other Chemistry topics for JEE Main

Organic Chemistry

Inorganic Chemistry

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