Determine the pH of a Na_2HPO_4 solution in which the formal concentration of NaHPO_4 is F= 0.00183 M
H_3PO_4(aq) + H_2O <--> H_2PO4^- (aq) + H_3O^+(aq) Ka1= 7.11x 10^-3
H_2PO_4^-(aq) + H_2O <--> HPO4^-2 (aq) + H_3O^+(aq) Ka2= 6.34 x 10^-8
HPO_4^-2(aq) + H_2O <--> PO4^-3 (aq) + H_3O^+(aq) Ka3= 4.22 x 10^-13