Question

The following reaction is exothermic. Which change will shift the equilibrium to the left? 2 SO₂(g) + O₂(g) ⇌ 2 SO₃(g)

1) Decreasing the temperature
2) Increasing the pressure
3) Adding a catalyst
4) Removing some SO₃(g)

Answer 1

Decreasing volume shifts equilibrium to the right; Increasing temperature shifts equilibrium to the right.

Step-by-step explanation:

Decreasing the volume leads to an increase in pressure which will cause the equilibrium to shift towards the side with fewer moles. In this reaciton, there are three moles on the reactant side and two moles on the product side, so the new equilibrium will shift towards the products (to the right).

Raising the temperature of the system is akin to increasing the amount of a reactant, and so the equilibrium will shift to the right. Lowering the system temperature will likewise cause the equilibrium to shift left. For exothermic processes, heat is viewed as a product of the reaction and so the opposite temperature dependence is observed.