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In a closed system, aqueous iron (III) chloride reacts withhydrogen sulphide gas as shown in the equation below.
#2FeCl_3(aq)+H_2S(g)overset(rightarrow)(leftarrow)2FeCl_2(aq)+2HCl(aq)+S(s)#
State and explain the observation that would be made if dilute hydrochloric acid is added the system at equilibrium.

Answer Text:
- The brown colour of the mixture intensifies and the green colour of the mixture fades. This is because addition of hydrochloric acid increases the concentration of HCl hence making the equilibrium shift to the left.