17. Acid and Base Equilibrium

Which of the following diprotic acid would produce the most acidic solution when dissolved?

Determine the pH of 0.115 M Na₂S. Hydrosulfuric acid, H₂S, possesses K_a1 = 1.0 × 10⁻⁷ and K_a2 = 9.1 × 10⁻⁸.