Question

Calculate the concentration of S^2- in an aqueous solution of 0.0196 M hydrosulfuric acid, H₂S (aq).

Calculate the concentration of HS^- in an aqueous solution of 7.73×10^-2 M hydrosulfuric acid, H₂S (aq).

Answer 1

Answer-

consider the diassociation reaction of H₂S

H₂S + H₂O -------> S^2- + 2H⁺

H₂S + H₂O -------> HS^- + H⁺

Since one mole of H₂S gives out 2 mole of H+ and one moles of HS^-

0.0196 M H₂S (aq) gives out upon complete which is same concetration as S^2-

[S^2-] =0.0196 M

7.73×10^-2 M hydrosulfuric acid, H2S(aq).

so, [HS^- ] =  7.73×10^-2 M

Note -I assumed that dissociation  reaction dissociate completely otherwise we need equlibrium constant in both thge cases.