For the reaction H2(g) + I2(g) ⇌ 2HI(g), if the temperature is increased and Kc

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Question: For the reaction H2(g) + I2(g) ⇌ 2HI(g), if the temperature is increased and Kc decreases, what does this indicate about the reaction?

Options:

Correct Answer: Exothermic

Solution:

A decrease in Kc with an increase in temperature indicates that the reaction is exothermic.

For the reaction H2(g) + I2(g) ⇌ 2HI(g), if the temperature is increased and Kc decreases, what does this indicate about the reaction?

For the reaction H2(g) + I2(g) ⇌ 2HI(g), if the temperature is increased and Kc decreases, what does this indicate about the reaction?

Step 1: Understand what Kc means. Kc is the equilibrium constant for a reaction, which tells us the ratio of products to reactants at equilibrium.
Step 2: Recognize that the reaction given is H2(g) + I2(g) ⇌ 2HI(g). Here, H2 and I2 are reactants, and HI is the product.
Step 3: Note that increasing the temperature can affect the position of equilibrium and the value of Kc.
Step 4: When the temperature increases and Kc decreases, it means that the concentration of products (HI) is lower compared to the reactants (H2 and I2) at the new temperature.
Step 5: Understand that if Kc decreases with an increase in temperature, it suggests that the forward reaction (producing HI) is less favored at higher temperatures.
Step 6: Recall that in exothermic reactions, heat is released when products are formed. Therefore, increasing the temperature shifts the equilibrium to favor the reactants.
Step 7: Conclude that a decrease in Kc with an increase in temperature indicates that the reaction is exothermic.

Le Chatelier's Principle – This principle states that if a dynamic equilibrium is disturbed by changing the conditions, the position of equilibrium shifts to counteract the change.
Equilibrium Constant (Kc) – Kc is a measure of the ratio of the concentrations of products to reactants at equilibrium, and its value is affected by temperature.
Exothermic Reactions – Exothermic reactions release heat, and an increase in temperature typically shifts the equilibrium position to favor the reactants, resulting in a decrease in Kc.