Question

why CO Is a better reducing agent than carbon at high temperature

Answer 1

Both thermodynamic and kinetic factors make carbon monoxide (CO) a better reducing agent than carbon.

When coke or coal is used to reduce a metal oxide, it gets oxidized to CO. And, when CO itself is the reducing agent, it is oxidized to CO2 .

MO + C = M + CO ; MO + CO = M + CO2

Thermodynamically, CO2 is much more stable than CO, as evident from the vast difference in their standard heats of formation. So, the second reaction with CO as the reducing agent is more favourable than the first one.

Metal oxides are solids at normal conditions, and so their reduction with carbon (having a high melting point) is a solid-solid interaction. But, when CO is the reducing agent, the process becomes a solid-gas interaction that is more vibrant and effective at a high temperature. Thus, kinetic factors also favour CO as a better reducing agent in metallurgy.

Answer 2

Explanation:

You can find this answer by simply looking at the Ellingham diagram. Which says that ∆G◦ of CO is much more negative than ∆G◦ of carbon. Thus the net reaction while reducing becomes negative and hence spontaneous and easily feasible.