Question

Which of the following changes alone would cause increase in the value of the equilibrium constant of the reaction? 
\(PCl_5(g) \rightarrow PCl_3(g) + Cl_2(g); \Delta H>0\)

• A. Increasing the volume of the reaction vessel
• B. Decreasing the volume of the reaction vessel
• C. ddition of catalyst to equilibrium mixture
• D. Addition of \(PCl_5(g)\) to the equilibrium mixture
• E. Increasing the temperature

Hint:

Always consider the sign of \(\Delta H\) when predicting the effects of temperature changes on equilibrium.

Answer 1

Answer: (E)

Step 1: The reaction \(PCl_5(g) \rightarrow PCl_3(g) + Cl_2(g)\) is endothermic (\(\Delta H>0\)). 
Step 2: According to Le Chatelier’s Principle, increasing the temperature of an endothermic reaction shifts the equilibrium to the right, favoring the formation of products. 
Step 3: This shift increases the equilibrium constant \(K\), as \(K\) is a measure of product favorability at equilibrium. 
Step 4: Therefore, increasing the temperature is the only option listed that will increase the equilibrium constant for this reaction.