Carbon monoxide is more effective reducing agent than carbon below 984 K but above this temperature the reverse is ture. How would you explain this?

Explanation

The two reactions are as:
`C_((s)) +O_(2) rarr CO_(2)` ....(i)
`2C_((s)) +O_(2) rarr 2CO` ...(ii)
`2CO +O_(2) rarr 2CO_(2)` ....(iii)

Below `983K` reaction `2CO +O_(2) rarr 2CO_(2)` is more favoured due to more negative `DeltaG` value thus `CO` is better reducing agent than carbon.
Above `983K`, reaction `2C_((s)) +O_(2) rarr 2CO` has more negative `DeltaG` than oxidation of `CO` to `CO_(2)`, so carbon will be better reducing agent.