How did the concentration of Cl2 change compared to the first equilibrium?

Question

2HCl(g) + I₂(s) ⇌ 2HI(g) + Cl₂(g)

When the reaction is at equilibrium, some amount of HI is added. The system reaches a new equilibrium state.

how did the concentration of Cl₂ change compared to the first equilibrium? 

Answer 1

LeChatelier’s Principle

After addition of HI, the concentration of Cl₂ will be less as the equilibrium shifts to to the left to alleviate the stress put on the system.