The molar mass of the water insoluble product formed from the fusion of chromite ore (FeCr₂O₄) with Na₂CO₃ in presence of O₂ is \underline\hspace2cm g mol⁻¹.

D and F Block Elements PYQ — JEE Main 2025 · 29 Jan · Shift 1 · Q21 with Solution

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Correct answer: 160

Identify the reaction during fusion of chromite ore

Chromite ore is $\mathrm{FeCr_2O_4}$ . On fusion with $\mathrm{Na_2CO_3}$ in presence of $\mathrm{O_2}$ , chromium is oxidized to chromate and iron is converted to ferric oxide.

A commonly written balanced reaction is:

4\mathrm{FeCr_2O_4} + 8\mathrm{Na_2CO_3} + 7\mathrm{O_2} \rightarrow 8\mathrm{Na_2CrO_4} + 2\mathrm{Fe_2O_3} + 8\mathrm{CO_2}

Find the water-insoluble product

In this reaction:

$\mathrm{Na_2CrO_4}$ is water soluble.
$\mathrm{Fe_2O_3}$ is water insoluble.

So the required water-insoluble product is ferric oxide, $\mathrm{Fe_2O_3}$ .

Calculate its molar mass

Using atomic masses:

$\mathrm{Fe} = 56$
$\mathrm{O} = 16$

Therefore,

M(\mathrm{Fe_2O_3}) = 2(56) + 3(16)

= 112 + 48 = 160\ \text{g mol}^{-1}

Final answer

The molar mass of the water-insoluble product is:

\boxed{160}

Comparison with stored answer

Stored correct answer = $160$

Our derived answer also = $160$ , so they agree.

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