20 mL of 0.1 M H2SO4 solution is added to 30 mL of 0.2 M NH4OH solution. The pH of the resultant mixture is [pKb of NH4OH = 4.7]

Given pKb of NH4OH = 4.720 mL of 0.1 M H2SO4 ⇒ nH+ = 430 ml 0.2 M NH4OH ⇒ nNH4OH = 6Solution is basic buffer.pOH = pKb + log [NH4+]/[NH4OH] = 4.7 + log (4/2)= 4.7 + log 2= 4.7+0.3= 5pH = 14-pOH= 14-5 = 9