nH+=nHCl=0.1x0.02=0.002mol，nOH-=2nBa(OH)2=2x0.05x0.03=0.003mol，H++OH-=H2O，反应后剩余nOH-=0.003-0.002=0.001mol，体积0.02+0.03=0.05升，cOH-=0.001/0.05=0.02molL-，POH=1.7，PH14-1.7=12.3
