JEE Main levelSingle correct optionDifficulty 2 of 3mt136
In an Ellingham diagram the line for 2C+OX22CO slopes downwards while the lines for most metal oxides slope upwards. The reason is that
Acarbon has a lower melting point than most metals
Bthe formation of CO is endothermic while that of metal oxides is exothermic
Cthe carbon reaction increases the number of moles of gas, whereas oxide formation from a metal consumes gaseous oxygen
DCO is more stable than any metal oxide at all temperatures
Answer: C
The slope equals −ΔS∘. For 2C+OX22CO, ΔS∘>0 (one mole of gas gives two), so the line falls. For 2M+OX22MO the gas is lost, ΔS∘<0, and the line rises.