20ml of 0.1M H2SO4 solution is added to 30ml of 0.2M NH4OH solution. The pH of resultant mixture is ( pKb of NH4OH= 4.7 )

H2SO4 +  2NH4OH  →  NH42SO4+2H2O                 Given :                20ml of 0.2N +  30ml of 0.2Nno.of milliequivalents =            4                        6In an equation the  no.of milliequivalents should be samei.e    no.of milliequivalents of  acid =no.of milliequivalents of base = no.of milliequivalents of salt formed (VN)=4no.of milliequivalents of base remains = 6-4 =2Here , VANA < VBNBHence   POH=Pkb+logsaltbase                     =4.7+log42=4.7+0.3=5     PH = 14-5 =9