Cu2S (Cu=63.5, S=32) is oxidised by acidified KMnO4 to Cu^2+ and SO2. Calculate the mass of KMnO4 (molar mass 158 g mol^-1) required to oxidise 0.795 g of Cu2S, in grams (two decimals).

JEE Advanced levelNumerical answerDifficulty 3 of 3eq032

$Cu X_{2} S$ ( $Cu = 63.5$ , $S = 32$ ) is oxidised by acidified $KMnO X_{4}$ to $Cu X^{2 +}$ and $SO X_{2}$ . Calculate the mass of $KMnO X_{4}$ (molar mass $158 g mo l^{- 1}$ ) required to oxidise $0.795 g$ of $Cu X_{2} S$ , in grams (two decimals).

Numerical answer type, answer in g, tolerance 0.01.

Per

Cu X_{2} S

2 Cu X^{+} \to 2 Cu X^{2 +}

loses

2

^{-}

and

S X^{2 -} \to S X^{4 +}

(in

SO X_{2}

) loses

6

^{-}

, so

n = 8

. Molar mass

= 159

, equivalent mass

= 19.875

, equivalents

= 0.795/19.875 = 0.040

. Equivalent mass of

KMnO X_{4} = 31.6

, so mass

= 0.040 \times 31.6 = 1.264 g