UPSC CDS 1 2018 GK Paper

Among the given options, option (b) will be the correct value of coefficients to balance the given chemical reaction.
2Fe2O3+6CO→4Fe+6CO2
When you divide by 2, we will have
Fe2O3+3CO→2Fe+3CO2
So, a=1, b=3, c=2, d=3
We need to make sure that the numbers are balanced on each side. We should start with the limiting element (in this case carbon). From there, we can work through the rest. The given reaction presents the case of reaction in the blast furnace. Here, it is so hot that carbon monoxide can be used, in place of carbon, to reduce the iron (III) oxide:
Iron (III) oxide + carbon monoxide→ iron + carbon dioxide