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In the thermite (aluminothermic) process, chromium is obtained from chromic oxide because
A$Cr_2O_3$ is more stable than $Al_2O_3$ and stays intact
Baluminium has a much higher melting point than chromium
C$Al_2O_3$ is more stable than $Cr_2O_3$, so Al reduces it
Dchromium is far more electropositive than aluminium metal
Answer & Solution
Correct answer: C. $Al_2O_3$ is more stable than $Cr_2O_3$, so Al reduces it
1. A metal can reduce the oxide of another metal whose oxide is **less stable** (lies above it in the Ellingham diagram).
2. $Al_2O_3$ is more stable (more negative $\Delta G_f$) than $Cr_2O_3$, so the reaction $Cr_2O_3 + 2Al \rightarrow 2Cr + Al_2O_3$ is favourable.
3. The large heat released keeps the chromium molten.
_Source: Samacheer Kalvi Class 12 Chemistry Vol.1, Unit 1 'Metallurgy', §1.3.2 (Reduction by metal)_
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