Question

Which of the following statements is/are correct regarding the following diagram of reduction of haematite?

• A. Below 1073 K, $C$ is a better reducing agent.
• B. Below 1073 K, $CO$ is a better reducing agent.
• C. Above 1073 K, $C$ is a better reducing agent.
• D. Haematite can’t be reduced by $C$ or $CO$.

Answer 1

Answer: (B), (C)

Above 1073 K, $C$ is a better reducing agent.

Below 1073 K, the Gibbs energy of formation of $F{e}_2{O}_3$ is -500 which is more than Gibbs energy of formation of $C{O}_2$. Thus $C{O}_2$ is more stable below 1073 K. As a result $F{e}_2{O}_3$ is reduced by $CO$.

Above 1073 K, the Gibbs energy of formation of $CO$ is more negative (or lesser) than that of $C{O}_2$ and $F{e}_2{O}_3$ i.e. the curve of formation of $CO$ is below the two other curves, means $C$ is able to reduce $F{e}_2{O}_3$ above 1073 K.

Therefor options $\left(b\right)$ and $\left(c\right)$ are correct.