x^2 = H+ ^2 = 0.6*1.3*10^-5 hence H+ = 0.00134 M now OH- = 0.07 M total OH- = 0.07 * 20 - 0.00134*50 /(70) = 0.0194 hence total H+ = 5.15*10(-13) hence pH = - logH+ = -log 5.15*10(-13) = 12.28 Solution x^2 = H+ ^2 = 0.6*1.3*10^-5 hence H+ = 0.00134 M now OH- = 0.07 M total OH- = 0.07 * 20 - 0.00134*50 /(70) = 0.0194 hence total H+ = 5.15*10(-13) hence pH = - logH+ = -log 5.15*10(-13) = 12.28.