The molar mass of the water insoluble product formed from the fusion of chromite ore $\left(\mathrm{FeCr}_{2} \mathrm{O}_{4}\right)$ with $\mathrm{Na}_{2} \mathrm{CO}_{3}$ in presence of $\mathrm{O}_{2}$ is ______ $\mathrm{g} \mathrm{mol}^{-1}$.

JEE Main · 2025 · 29 Jan 2025 · Shift 1 · General Principles and Processes of Isolation of Metals

The molar mass of the water insoluble product formed from the fusion of chromite ore

(FeCr_{2} O_{4})

with

Na_{2} CO_{3}

in presence of

O_{2}

is ______

g mol^{- 1}

Answer: 160

Fusing chromite ore,

FeCr_{2} O_{4}

, with

Na_{2} CO_{3}

in the presence of

O_{2}

oxidises chromium(III) to chromium(VI) and converts the iron to ferric oxide:

4 FeCr_{2} O_{4} + 8 Na_{2} CO_{3} + 7 O_{2} \to 8 Na_{2} CrO_{4} + 2 Fe_{2} O_{3} + 8 CO_{2}

Sodium chromate is water soluble while ferric oxide is not. The molar mass of

Fe_{2} O_{3}

2 (56) + 3 (16) = 112 + 48 = 160 g mol^{- 1}

JEE Main · 2025 · 29 Jan 2025 · Shift 1 · Integer answer