If it is known that `H_2S` is a weak acid that ionizes to form `2H^+` and `S^(2-)` , lowering the pH of a solution of `H_2S` by adding HCl would

Options

A. lower the `S^(2-)` concentration
B. have no effect on `S^(2-)` concentration
C. raise the `S^(2-)` concentration
D. not be possible.

Answer

A

Explanation

`H_2S undersetlarrto 2H^+ + S^(2-)` By the common ion effect, lowering the pH (increasing the `H^+` concentration) will lower the `S^(-2)` concentration by displacing the reaction to the left `K_i=((H^(+2))(S^(2-)))/((H_2S))` If `H^+` increases, `S^(-2)` must decrease