Question

The chemical reaction of a gas phase is given below. \[ 2A(g) + B(g) \rightleftharpoons C(g) + D(g) \] Which one of the following changes will affect the value of \(K_c\)?

• A. Addition of inert gas
• B. Increasing in temperature
• C. Addition of reactants
• D. Addition of catalyst

Hint:

\(K_c\) is constant for a given reaction at a given temperature. Only temperature can change its value.

Answer 1

The Correct Option is B

The given chemical reaction in gas phase is:

\(2A(g) + B(g) \rightleftharpoons C(g) + D(g)\)

We need to determine which of the following changes will affect the equilibrium constant \(K_c\). Let's go through each option:

1. Addition of inert gas:
   • Adding an inert gas at constant volume does not alter the concentrations of reactants or products in the reaction mixture. Therefore, the equilibrium constant \(K_c\), which is dependent on concentration, remains unchanged.
2. Increasing in temperature:
   • The equilibrium constant \(K_c\) is temperature-dependent. A change in temperature alters the equilibrium position, which is reflected by a change in the value of \(K_c\). The direction of shift depends on the reaction's enthalpy (exothermic or endothermic).
3. Addition of reactants:
   • While adding reactants will shift the position of equilibrium (principle of Le Chatelier), it does not change the value of the equilibrium constant \(K_c\), as \(K_c\) is only a function of temperature.
4. Addition of catalyst:
   • A catalyst speeds up the rate of both the forward and reverse reactions equally without affecting the equilibrium position or the equilibrium constant \(K_c\).

Based on the explanations above, the only factor that affects the value of \(K_c\) is a change in temperature.

Correct Answer: Increasing in temperature