Question

For the reaction H₂(g) + Cl₂(g) ⇌ 2HCl(g) + heat, predict the direction of the reaction for the following scenarios:

(a) What happens if heat is removed?
(b) What happens if HCl is added?
(c) What happens if H₂ is added?
(d) What happens if pressure is decreased?

Answer 1

If heat is removed, the reaction shifts forward to produce more HCl. If HCl is added, the reaction shifts in reverse to consume some of the added HCl. If H₂ is added, the reaction shifts forward to consume some of the added H₂.

Step-by-step explanation:

(a) If heat is removed from the reaction H₂(g) + Cl₂(g) ⇌ 2HCl(g) + heat, the reaction will shift in the direction that produces heat to compensate for its removal. Therefore, the reaction will shift in the forward direction to produce more HCl(g).

(b) If HCl is added to the reaction, the reaction will shift in the direction that consumes HCl to restore equilibrium. Therefore, the reaction will shift in the reverse direction to consume some of the added HCl.

(c) If H₂ is added to the reaction, the reaction will shift in the direction that consumes H₂ to restore equilibrium. Therefore, the reaction will shift in the forward direction to consume some of the added H₂.

(d) If the pressure is decreased, the reaction will shift in the direction that reduces the number of moles of gas to restore equilibrium. In this case, that would be the reverse reaction where HCl(g) and Cl₂(g) react to produce H₂(g) and Cl₂(g), reducing the amount of gas in the system.