What can be said about the reaction [tex]2 NH_3(g) \rightarrow N_2(g) + 3 H_2(g), \Delta H = 92.4 \, kJ/mol[/tex]?

A. The reaction is exothermic.
B. The reaction is endothermic.
C. The forward direction is favored.
D. The reaction produces heat.



Answer :

To determine the nature of the reaction

[tex]\[2 \text{NH}_3(g) \rightarrow \text{N}_2(g) + 3 \text{H}_2(g), \Delta H = 92.4 \, \text{kJ}/\text{mol}\][/tex]

we need to consider the value and sign of [tex]\(\Delta H\)[/tex].

### Step-by-Step Solution:

1. Understanding [tex]\(\Delta H\)[/tex]:

- [tex]\(\Delta H\)[/tex] represents the enthalpy change of the reaction. It indicates the amount of heat absorbed or released during a chemical reaction at constant pressure.

2. Significance of [tex]\(\Delta H = 92.4 \, \text{kJ}/\text{mol}\)[/tex]:

- The given value of [tex]\(\Delta H\)[/tex] is [tex]\(92.4 \, \text{kJ}/\text{mol}\)[/tex].
- The sign of [tex]\(\Delta H\)[/tex] is positive.

3. Interpreting the Positive [tex]\(\Delta H\)[/tex]:

- When [tex]\(\Delta H\)[/tex] is positive, it means that the system absorbs heat from the surroundings. This is characteristic of an endothermic reaction.

- An endothermic reaction requires energy input to proceed, as it consumes heat.

4. Conclusions Based on [tex]\(\Delta H\)[/tex]:

- Since [tex]\(\Delta H = 92.4 \, \text{kJ}/\text{mol}\)[/tex] and is positive, we can conclude that:

B. The reaction is endothermic.

### Final Answer:

[tex]\[ \boxed{B. \text{The reaction is endothermic.}} \][/tex]

The positive value of [tex]\(\Delta H\)[/tex] confirms that the reaction absorbs heat, fitting the description of an endothermic process.