H3PO4+NaOH==NaH2PO4+H2O反应后有0.0025mol H3PO4和0.0025mol NaH2PO4H3PO4的存在抑制了H2PO4-的电离[H+]*[H2PO4-]=6.9*10^(-3)[H2PO4-]=[H+]+0.0025/0.075得[H+]=0.068mol/LpH=1.17
磷酸是中强酸不能完全电离，不好算呀兄弟
