At 25°C, the reaction: 2ICl(g) + heat ⇌ I2(g) + Cl2(g)

Question

has a K value of 6.2 × 10–6.
Which of the following would be true if the temperature were decreased to 10°C?

1. The value of K would be larger.
2. The concentration of ICl would increase.
3. The concentration of I2 would increase.
Question 4 options:

2 only

1 and 3 only

3 only

1 and 2 only

1 only

Answer 1

To analyze the effect of decreasing the temperature on the equilibrium of the reaction

\[ 2ICl(g) + \text{heat} \rightleftharpoons I_2(g) + Cl_2(g) \]

we can apply Le Chatelier's principle. In this reaction, heat is treated as a product since it is written on the right side of the equilibrium equation.

1. The value of K would be larger.
   When the temperature is decreased, the equilibrium will shift to the left to produce more heat (i.e., favor the exothermic direction). Therefore, the equilibrium constant \( K \) will decrease, not increase. This statement is incorrect.

2. The concentration of ICl would increase.
   As the equilibrium shifts to the left (to favor ICl), the concentration of ICl will indeed increase. This statement is correct.

3. The concentration of I2 would increase.
   As the equilibrium shifts to the left, the concentration of I2 will decrease. This statement is incorrect.

Given this analysis, the correct answer is:

2 only