In the important industrial process for producing ammonia (the Haber Process), the overall reaction is given by:

[tex]\[ N_2(g) + 3H_2(g) \rightarrow 2NH_3(g) + 100.4 \text{ kJ} \][/tex]

A yield of \(\text{NH}_3\) of approximately \(98\%\) can be obtained at \(200^{\circ}C\) and 1,000 atmospheres of pressure. What is the \(\Delta H\) in \(\text{kJ}\) of heat released per mole of \(\text{NH}_3(g)\) formed?

A. \(-100.4 \text{kJ}\)

B. \(-50.2 \text{kJ}\)

C. \(50.2 \text{kJ}\)

D. [tex]\(100.4 \text{kJ}\)[/tex]



Answer :

To solve the problem of finding the \(\Delta H\) in \( \text{kJ} \) of heat released per mole of \( \text{NH}_3 \) formed in the Haber Process, let's break it down step by step.

Given:
[tex]\[ N_2(g) + 3H_2(g) \rightarrow 2NH_3(g) + 100.4 \; \text{kJ} \][/tex]

This tells us that the reaction yields 100.4 kJ of energy when 2 moles of \( \text{NH}_3 \) are produced. We need to find the heat released per mole of \( \text{NH}_3 \).

Step-by-Step Solution:

1. Determine the total heat released for the reaction:
The overall reaction releases 100.4 kJ of energy.

2. Identify the amount of \( \text{NH}_3 \) produced:
According to the equation, 100.4 kJ is released when 2 moles of \( \text{NH}_3 \) are formed.

3. Calculate the heat released per mole of \( \text{NH}_3 \):
To find the heat released per mole, we divide the total heat by the number of moles of \( \text{NH}_3 \) produced.
[tex]\[ \Delta H_{\text{per mole of NH}_3} = \frac{100.4 \; \text{kJ}}{2 \; \text{moles of NH}_3} = 50.2 \; \text{kJ per mole of NH}_3 \][/tex]

4. Consider the direction of the heat flow:
The question specifies that the heat is released, meaning it is an exothermic reaction. Thus, the enthalpy change \(\Delta H\) should be negative when considering the perspective of the reaction.
[tex]\[ \Delta H_{\text{per mole of NH}_3} = -50.2 \; \text{kJ per mole of NH}_3 \][/tex]

Therefore, the \(\Delta H\) of heat released per mole of \( \text{NH}_3 \) formed is \(-50.2 \; \text{kJ}\). The correct answer is:
[tex]\[ \boxed{-50.2 \; \text{kJ}} \][/tex]