Acidified KMnO4 (36.0 mL of 0.0500 M) just oxidises a sample of Cu2S to Cu^2+ and SO2. Using Cu=63.5 and S=32, find the mass of Cu2S in the sample, in mg to the nearest integer.

JEE Advanced levelNumerical answerDifficulty 3 of 3eq182

Acidified $KMnO X_{4}$ ( $36.0 mL$ of $0.0500 M$ ) just oxidises a sample of $Cu X_{2} S$ to $Cu X^{2 +}$ and $SO X_{2}$ . Using $Cu = 63.5$ and $S = 32$ , find the mass of $Cu X_{2} S$ in the sample, in $mg$ to the nearest integer.

Numerical answer type, answer in mg, tolerance 2.

n-factor of

Cu X_{2} S

: Cu gives 2 electrons and S (

- 2 \to + 4

) gives 6, so n

= 8

. Electrons taken by permanganate

= 36.0 \times 0.0500 \times 5 = 9.00

mmol. Moles of

Cu X_{2} S

= 9.00/8 = 1.125

mmol; mass

= 1.125 \times 159 = 178.9 mg