UPSC Combined Geo-Scientist, Mains · 2017 · Mains Paper III

Q1(a). Copper oxide mixture

Question

A 10.50 g mixture of CuO and Cu₂O yields 8.66 g Cu on reduction. Find the original masses.

CuO = 7.456 g; Cu₂O = 3.044 g (using Cu 63.546 and O 15.999).

Let the CuO mass be x g and Cu₂O mass be (10.50-x) g.
Their copper mass fractions are 63.546/79.545 and 127.092/143.091. Thereforex63.546/79.545+(10.50-x)127.092/143.091=8.66.
Solving gives x=7.4562 g. The complementary mass is 3.0438 g.
The total oxygen removed is 10.50-8.66=1.84 g, consistent with the two oxide amounts. Slight changes arise from rounded atomic weights.

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