Q40 / 125 · BITSAT 2014 · Chemistry

$3.92 \mathrm{~g}$ of ferrous ammonium sulphate react completely with $50 \mathrm{ml} \frac{\mathrm{N}}{10} \mathrm{KMnO}_{4}$ solution. The percentage purity of the sample is

  • Correct answer
    A
    50
  • B
    78.4
  • C
    80
  • D
    39.2

Solution

Eq of $\mathrm{KMnO}_{4}$ used $=\frac{50 \times 1}{1000 \times 10}=0.005$ $\therefore$ Eq of FAS reacted $=0.005$ $\therefore$ weight of FAS needed $$ =0.005 \times 392=1.96 \mathrm{~g} $$ Thus percentage purity of FAS is $50 \%$

Hence, the correct answer is option: 'A'.

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