A 2.0g sample containing MnO_2 is treated… - JEE Main 2022 Chemistry PYQ

JEE Main 2022 — Chemistry Physical Chemistry

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A $2.0g$ sample containing ${\mathrm{MnO}}_{2}$ is treated with $\mathrm{HCl}$ liberating ${\mathrm{Cl}}_{2}$ . The ${\mathrm{Cl}}_{2}$ gas is passed into a solution of $\mathrm{KI}$ and $60.0\mathrm{mL}$ of $0.1{\mathrm{MNaS}}_{2}{O}_{3}$ is required to titrate the liberated iodine. The percentage of ${\mathrm{MnO}}_{2}$ in the sample is____. Nearest integer)

[Atomic masses (in $u$ ) $\mathrm{Mn}=55;\mathrm{Cl}=35.5:O=16,I=127,\mathrm{Na}=23,K=39,S=32$ ]

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Held on 28 Jun 2022 · Verified 6 Jul 2026.

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Solution

${\mathrm{MnO}}_{2}+4\mathrm{HCl}\longrightarrow {\mathrm{MnCl}}_{2}+{\mathrm{Cl}}_{2}(g)+2{H}_{2}O$

${\mathrm{Cl}}_{2}+2\mathrm{Kl}\longrightarrow {I}_{2}+2\mathrm{KCl}$

${I}_{2}+2{\mathrm{Na}}_{2}{S}_{2}{O}_{3}\longrightarrow 2\mathrm{Nal}+{\mathrm{Na}}_{2}{S}_{4}{O}_{6}$

Mili eq. of ${\mathrm{MnO}}_{2}=$ Mili eq. of ${\mathrm{Cl}}_{2}=$ Mili eq. of ${I}_{2}=$ Mili eq. of Hypo.

$2(\frac{w}{87})=[0.1\times 60]$

$W=261$ miligram

$%\mathrm{of}{\mathrm{MnO}}_{2}=\frac{0.261}{2}\times 100=13.05%\approx 13$

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