What is the pH of a 25 ml sample of 0.2 M sulfuric acid? What is the pH after 5 ml of 0.25 M sodium hydroxide is added?

H₂SO₄ fully dissociates into ions (strong acid). It is diprotic therefore concentration of H⁺ ions is twice that of the acid = 0.4 M. pH = -log[H⁺] = -log[0.4] = 0.3979... = 0.40 to 2 d.pOH^- ions react with H⁺ ions to produce water. Therefore (moles of H⁺) - (moles of OH⁺) = (moles of H⁺ remaining in solution).= 5 x 10^-3 moles (of H⁺) - 1.25 x 10^-3 moles (of OH^-) = 3.75 x 10^-3 moles remaining.Conc. of H⁺ = n/V = 0.125 M. pH = -log[0.125] = 0.90 to 2 d.p