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. What is the weight (in $\mathrm{kg}$ ) of $\mathrm{Pb}$ produced per $\mathrm{kg}$ of $\mathrm{O}_{2}$ consumed? (Atomic weights in $\mathrm{g} \mathrm{mol}^{-1}: \mathrm{O}=16, \mathrm{~S}=32, \mathrm{~Pb}=207$ )

JEE · Chemistry · previous-year question