Question

In $\text{NH}_3$ synthesis by Haber’s process, what is the effect on the rate of the reaction with the addition of Mo and CO, respectively?

• A. Increases and decreases
• B. Decreases and decreases
• C. Decreases and increases
• D. Both Mo and CO increases the rate
• E. Both Mo and CO does not affect the rate

Hint:

Always ensure your feed gases (N\(_2\) and H\(_2\)) are pure in industrial settings; even trace amounts of CO or H\(_2\)S can permanently damage the expensive iron catalyst.

Answer 1

The Correct Option is A

Concept: The Haber Process utilizes a catalyst to lower the activation energy of the reaction between nitrogen and hydrogen. External substances can either assist or hinder this catalytic activity.

Step 1: Role of Molybdenum (Mo).
In the synthesis of ammonia, iron (Fe) serves as the primary catalyst. Molybdenum (Mo) acts as a promoter. Promoters are substances that are not catalysts themselves but increase the efficiency and rate of the catalyst. Thus, Mo increases the rate.

Step 2: Role of Carbon Monoxide (CO).
Carbon monoxide (CO) behaves as a catalytic poison. It bonds strongly to the iron surface, blocking the sites where \( N_2 \) and \( H_2 \) would otherwise react. This effectively "kills" the catalyst's activity, thereby decreasing the rate of reaction.

Step 3: Final Conclusion.
Adding Mo increases the rate, while adding CO decreases it. This corresponds to option (A).