Consider each of the following systems at equilibrium. The temperature is kept constant, and in each case the reactants are in a cylinder fitted with a movable piston. For which system (s) will a decrease in pressure favor the formation of products? Check all that apply. (a) A (s) ⇌2B (s) (b) 2A (l) ⇌B (l) (c) A (g) ⇌B (s) (d) 2A (g) ⇌B (g) (e) A (g) ⇌2B (g)

The correct option is: (e) A (g) ⇌2B (g)

Explanation:

According to the Le Chatelier's principle, for a gaseous system at equilibrium, the change in the pressure of the system causes the equilibrium to change in the direction that reduces or counteracts the change in the pressure.

According to the ideal gas equation: PV = nRT

⇒ pressure (P) ∝ (n) number of moles of gas

Therefore, when the pressure of the system decreases, the equilibrium of the system shifts to the reaction side that increases the number of moles of gas. Thus increasing the pressure.

A (g) ⇌2B (g)

In the given reaction, the number of moles of gaseous products is greater than reactants. Therefore, when the pressure decreases, the direction of the equilibrium shifts towards the products side that has more number of moles of gas.

Therefore, for this system, decrease in the pressure, favors the product formation.