Consider the reaction below.

[tex]\[ 2 NH_{3(s)} \leftrightarrow N_{2(s)} + 3 H_{2(s)} \][/tex]

Which is most likely the effect on the forward reaction if there is an increase in pressure of the system?

A. The reactant surface area increases.
B. The reaction rate decreases.
C. The reaction is not affected at all.
D. The reaction stops completely.



Answer :

Let's analyze the chemical reaction:

[tex]\[ 2 \text{NH}_3(s) \leftrightarrow \text{N}_2(s) + 3 \text{H}_2(s) \][/tex]

Here, both the reactants and the products are in the solid state.

To determine how an increase in pressure affects this reaction, we must consider the nature of solids and pressure changes:

1. Pressure and Solids: Changes in pressure significantly affect gases due to their compressible nature, but solids are virtually incompressible. Thus, changes in pressure have very little effect on systems that involve only solids.

2. Effect of Increased Pressure:

- Surface Area: The surface area of a solid reactant is not directly influenced by changes in external pressure. Increasing pressure does not inherently change the surface area of the solid particles.

- Reaction Rate: Typically, the rate of a reaction involving only solids and their interactions does not decrease due to increased pressure. Pressure changes minimally impact the kinetics of reactions involving exclusively solid phases.

- Equilibrium Position: For reactions involving gases, increasing pressure would generally shift the equilibrium according to Le Chatelier's principle. However, for solid-solid equilibria, the system's response to pressure changes is negligible because solids are incompressible.

- Reaction Halting: An increase in pressure typically does not cause a reaction to stop completely unless the conditions are so extreme that the reactants or products undergo physical or chemical changes preventing the reaction.

Given the scenarios and the minimal impact of pressure changes on solid reactions, we can conclude:

The reaction is not affected at all.

Thus, the most likely effect on the forward reaction with an increase in pressure in this system is minimal or negligible. Therefore, the correct answer is:

The reaction is not affected at all.