What stress will shift the following equilibrium system to the right? 2SO2 (g) + O2 (g) ⇌ 2SO3 (g); ΔH = - 98.8 kJ/mol Decreasing concentration of SO2 Decreasing temperature Increasing concentration of SO3 Increasing volume

Decreasing temperature.

Explanation:

Le Châtelier's principle states that when there is an dynamic equilibrium, and this equilibrium is disturbed by an external factor, the equilibrium will be shifted in the direction that can cancel the effect of the external factor to reattain the equilibrium. The choices here:

1) Decreasing concentration of SO₂,

The concentration of SO₂ decreases, so the reaction will be shifted to the left direction to suppress the decrease in SO₂ concentration.

2) Decreasing temperature,

ΔH = - 98.8 kJ/mol, the negative sign means that the reaction is exothermic and release the heat.

If the temperature decreased, this means that the products decrease, so the reaction will shift to the right to suppress the decrease in temperature.

It is the right choice.

3) Increasing concentration of SO₃:

Increasing concentration of SO₃ will shift the reaction to the left to suppress the effect of increasing the concentration of SO₃.

4) Increasing volume:

Increasing the volume will decrease the pressure.

Decreasing the pressure will shift the reaction of gases to the side of higher no. of moles (left side).

So, the right choice is: Decreasing temperature.