Chemistry · Metallurgy

JEE Advanced 2018 — Paper 2 — Question 22

Galena (an ore) is partially oxidized by passing air through it at high temperature. After some time, the passage of

air is stopped, but the heating is continued in a closed furnace such that the contents undergo self-reduction.

The weight (in kg ) of Pb produced per kg of $\mathrm{O}_{2}$ consumed is $\_\_\_\_$ .

(Atomic weights in $\mathrm{g} \mathrm{mol}^{-1}: \mathrm{O}=16, \mathrm{~S}=32, \mathrm{~Pb}=207$ )

Answer: 6.47

Numerical answer — enter this value.

Given: 3 PbS + 3 O2 → 3 Pb + 3 SO2

From the reaction: 3 moles of O2 (96 g) produce 3 moles of Pb (3 × 207 = 621 g)

Now, for 1000 g (1 kg) of O2: Pb produced = (621 / 96) × 1000 = 6468.75 g = 6.47 kg

Correct answer: 6.47 kg

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