Question

An aqueous solution of hydrogen sulphide shows the equilibrium: `H_(2) S hArr H^(o+)+HS^(ɵ)`
If dilute hydrochloric acid is added to an aqueous solution of `H_(2)S`, without any change in temperature, the
a. The equilibrium constant will change.
b. The concentration `HS^(ɵ)` will increase.
c. The concentration of un-dissociated hydogen sulphide will decrease.
d. The concentration of `HS^(ɵ)` will decrease.

Answer 1

`H_(2)S(aq) hArr H^(o+)+(aq)+HS^(ɵ)(aq)`
Addition of dilute `HCl(aq)` will increase the concentration of `H^(o+)` ions in the solution leading to a backward shift in the reaction to re-establish the equilibrium state. This means the concentration of `HS^(ɵ)(aq)` will decrease.