Acidity of diprotic acids in aqueous solutions increases in the order:

For group 16 hydrides, acidic strength increases down the group. This is because as the size of the central atom ($S,Se,Te$) increases, the bond length with hydrogen increases and the bond dissociation energy decreases, making it easier to release $H^{+}$ ions.Order: ${\text{H}}_2\text{S}<{\text{H}}_2\text{Se}<{\text{H}}_2\text{Te}$.