Fe3O4 (molar mass 232 g mol^-1) is (i) oxidised completely to Fe2O3 by KMnO4 and (ii) reduced completely to Fe by hydrogen. The equivalent masses of Fe3O4 in (i) and (ii) are respectively:

JEE Advanced levelSingle correct optionDifficulty 3 of 3eq036

$Fe X_{3} O X_{4}$ (molar mass $232 g mo l^{- 1}$ ) is (i) oxidised completely to $Fe X_{2} O X_{3}$ by $KMnO X_{4}$ and (ii) reduced completely to $Fe$ by hydrogen. The equivalent masses of $Fe X_{3} O X_{4}$ in (i) and (ii) are respectively:

(i)

Fe X_{3} O X_{4}

FeO \cdot Fe X_{2} O X_{3}

, containing one

Fe X^{2 +}

which loses

1

^{-}

to become

Fe X^{3 +}

, so

n = 1

and equivalent mass

232

. (ii) Reduction to

3 Fe

: one

Fe X^{2 +}

gains

2

and two

Fe X^{3 +}

gain

6

, so

n = 8

and equivalent mass

232/8 = 29