Consider the following chemical reaction in a closed container:

CO(g) + 3H2(g) ⇌ CH4(g) + H2O(g)
Δ
H°rxn = –206 kJ·mol–1; Kc = 4.8
×
10–2 M–2

Predict the result of decreasing the temperature?

Question

Consider the following chemical reaction in a closed container:

CO(g) + 3H2(g) ⇌ CH4(g) + H2O(g)        
Δ
H°rxn = –206 kJ·mol–1;  Kc = 4.8 
×
 10–2 M–2

Predict the result of decreasing the temperature?

BlackTom AI · Accepted Answer

The question describes the equilibrium CO(g) + 3H2(g) ⇌ CH4(g) + H2O(g) with an exothermic reaction (ΔH°rxn = –206 kJ·mol–1). In a closed container, the effect of lowering the temperature on an exothermic equilibrium is to shift the position of equilibrium toward the products to release heat.

Since the reaction releases heat (exothermic), decreasing temperature favors the forward reaction, increasing the amount of CH4(g) (and H2O(g)) formed and reducing the amount of reactants CO(g) and H2(g).

Additionally, for exothermic processes, the equilibrium constant Kc tends to increase as the temperature decreases, which corresponds to a greater proportion of products at equilibrium. The provided Kc value (4.8 × 10–2 M–2) is a constant at a given temperature and would be larger at the lower temperature, reinforcing the shift toward products.

Option analysis:
- More CH4(g) is produced: This aligns with Le Chatelier’s principle for an exothermic reaction when temperature decreases; the system shifts to the right to produce more CH4 and H2O.

There are no other answer choices to evaluate in this item, so the statement given correctly describes the expected outcome of decreasing temperature for this exothermic equilibrium.

Consider the following chemical reaction in a closed container: CO(g) + 3H2(g) ⇌ CH4(g) + H2O(g) Δ H°rxn = –206 kJ·mol–1; Kc = 4.8 × 10–2 M–2 Predict the result of decreasing the temperature?单项选择题

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