Use the Henderson eqn: pOH = pKb + log(base/acid) pOH = -log(1.88 x 10^-5) + log(.750/.250) pOH = 5.20 pH + pOH = 14 pH + 5.20 = 14 pH = 8.8 Solution Use the Henderson eqn: pOH = pKb + log(base/acid) pOH = -log(1.88 x 10^-5) + log(.750/.250) pOH = 5.20 pH + pOH = 14 pH + 5.20 = 14 pH = 8.8.