Which of the following factors would affect the equilibrium constant?

Step 1: Analyze the question The question asks which factor changes the value of the equilibrium constant (K). Don't confuse this with factors that merely shift the position of equilibrium.

Step 2: The concept The equilibrium constant K is the ratio of product concentrations to reactant concentrations at equilibrium, for example:

For aA + bB ⇌ cC + dD, K = [C]^c[D]^d / [A]^a[B]^b

Using Le Chatelier's principle:

• Concentration: Changing a concentration shifts the equilibrium position, but the system readjusts until the ratio gives the same K.
• Pressure: Changing pressure shifts the position for gaseous reactions where the number of moles differs on each side, but K stays the same.
• Volume: This works the same way as pressure, so it shifts the position but K is unchanged.
• Temperature: Changing temperature changes K. Heat is effectively a reactant or product, and the energy change (ΔH) of the forward and reverse reactions differs. • Exothermic reactions: raising the temperature lowers K. • Endothermic reactions: raising the temperature raises K.

Step 3: Solve Only temperature changes the numerical value of K, so the answer is B. Temperature.

Tip: Remember "K depends on T only" (and not on concentration, pressure, volume, or the presence of a catalyst). A catalyst speeds up how fast equilibrium is reached, but it does not change K either. This is a favorite in WASSCE, JAMB, and NECO.