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Chapter 19: Problem 78

Indicate whether \(\Delta G\) increases, decreases, or does not change when the partial pressure of \(\mathrm{H}_{2}\) is increased in each of the following reactions: (a) \(\mathrm{N}_{2}(g)+3 \mathrm{H}_{2}(g) \longrightarrow 2 \mathrm{NH}_{3}(g)\) (b) \(2 \mathrm{HBr}(g) \longrightarrow \mathrm{H}_{2}(g)+\mathrm{Br}_{2}(g)\) (c) \(2 \mathrm{H}_{2}(g)+\mathrm{C}_{2} \mathrm{H}_{2}(g) \longrightarrow \mathrm{C}_{2} \mathrm{H}_{6}(g)\)

Short Answer

Expert verified
For the given reactions upon increasing the partial pressure of H₂: (a) ΔG decreases. (b) ΔG increases. (c) ΔG decreases.

Step by step solution

01

(a) Analyzing the increase in H₂ partial pressure in the first reaction

For reaction (a), N₂(g) + 3 H₂(g) → 2 NH₃(g), it is important to check how the reaction will shift when the partial pressure of H₂, one of the reactants, is increased. According to Le Chatelier's principle, when we increase the pressure (or concentration) of a reactant, the system will try to counteract the change by shifting towards the products. In this case, the reaction will shift to the right to produce more NH₃. Because the reaction shifts towards the products, this signifies ΔG for the reaction will decrease in value.
02

(b) Analyzing the increase in H₂ partial pressure in the second reaction

For reaction (b), 2 HBr(g) → H₂(g) + Br₂(g), when the partial pressure of H₂, one of the products, is increased, we'll evaluate how the reaction shifts according to Le Chatelier's principle. With the increase in the partial pressure of H₂, the system will attempt to counteract the change by shifting towards the reactants to consume the excess H₂. In this case, the reaction will shift to the left to produce more HBr. As the reaction shifts towards the reactants, this implies that ΔG for the reaction will increase in value.
03

(c) Analyzing the increase in H₂ partial pressure in the third reaction

For reaction (c), 2 H₂(g) + C₂H₂(g) → C₂H₆(g), we have to determine how a change in the partial pressure of H₂, one of the reactants, will influence the reaction's shift. As per Le Chatelier's principle, increasing the pressure (or concentration) of a reactant will drive the system to counteract the change by shifting towards the products. In this case, the reaction will shift to the right, forming more C₂H₆. The shift of the reaction toward the products suggests that ΔG for the reaction will decrease in value.
04

Summary

For the given reactions upon increasing the partial pressure of H₂: (a) ΔG decreases. (b) ΔG increases. (c) ΔG decreases.

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Most popular questions from this chapter

Consider a system consisting of an ice cube. (a) Under what conditions can the ice cube melt reversibly? (b) If the ice cube melts reversibly, is \(\Delta E\) zero for the process? Explain.

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