The correct option is B 9
Millimoles of H2SO4=20×0.1=2
Millimoles of NH4OH=30×0.2=6
H2SO4+2NH4OH→(NH4)2SO4+2H2O
Initial 2 6 0
Equilibrium 0 6−4=2 2
Total volume=30+20=50 mL
[(NH4)2SO4]=250 M∴ [NH+4]=250×2=450 M[NH4OH]=250 M
pOH=pKb+log[NH+4][NH4OH] =4.7+log450250pOH=4.7+log2≈5.0∴ pH=14−pOHpH=14−5=9.0