JEE Main 2022 · 28 Jun · Shift 1 · Chemistry Q81

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ChemistryInteger+4 / -1Question 81 of 90

A 2.0 g sample containing $\mathrm{MnO_2}$ is treated with HCl liberating $\mathrm{Cl_2}$ . The $\mathrm{Cl_2}$ gas is passed into a solution of KI and 60.0 mL of 0.1 M $\mathrm{Na_2S_2O_3}$ is required to titrate the liberated iodine. The percentage of $\mathrm{MnO_2}$ in the sample is ______. (Nearest integer)

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

Your answer

Answer and worked solution

Official answer: 13

Chain. 1 $\mathrm{MnO_2}$ → 1 $\mathrm{Cl_2}$ → 1 $\mathrm{I_2}$ → 2 $\mathrm{S_2O_3^{2-}}$ .

Moles. Thiosulfate $6\times10^{-3}$ , so $\mathrm{MnO_2}$ $3\times10^{-3}$ mol $=0.261$ g.

Percentage. $\frac{0.261}2\times100\approx13$ .

Answer: 13

Topics:Redox titrations Stoichiometry

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JEE Main 2022 · 28 Jun · Shift 1, Chemistry question 81