Question

For the reaction: \( \text{N}_2(g) + 3\text{H}_2(g) \rightarrow 2\text{NH}_3(g) \), the enthalpy change (\( \Delta H \)) is –92.4 kJ/mol. What type of reaction is it?

• A. Endothermic
• B. Exothermic
• C. Isothermal
• D. Photochemical

Hint:

Key Concept: \( \Delta H < 0 \) → Exothermic, \( \Delta H > 0 \) → Endothermic.

Answer 1

The Correct Option is B

To determine the type of reaction, we need to analyze the enthalpy change (\( \Delta H \)) provided: –92.4 kJ/mol. Here's how to interpret this:

1. Understand Enthalpy Change: The enthalpy change (\( \Delta H \)) indicates the amount of heat absorbed or released during a reaction. It is expressed in kilojoules per mole (kJ/mol).
2. Negative Enthalpy Change: A negative \(\Delta H\) value signifies that the reaction releases heat to the surroundings.
3. Exothermic Reaction: When a reaction releases heat (negative \(\Delta H\)), it is classified as exothermic.

Given that the enthalpy change is –92.4 kJ/mol, this reaction releases heat, classifying it as Exothermic.

Answer 2

The given chemical reaction is: 2N(g)+3H(g)→2NH3(g) with an enthalpy change (\(\Delta H\)) of –92.4 kJ/mol.

To determine the type of reaction, we analyze the sign of the enthalpy change (\(\Delta H\)):

• In an exothermic reaction, energy is released to the surroundings and \(\Delta H\) is negative.
• In an endothermic reaction, energy is absorbed and \(\Delta H\) is positive.
• An isothermal process is typically a physical process where temperature remains constant, not defined by \(\Delta H\).
• A photochemical reaction is driven by the absorption of light, not by \(\Delta H\).

Given that \(\Delta H = -92.4\) kJ/mol, it indicates the system releases energy. 
Thus, the reaction is exothermic.