The correct option is A 3.13
Given, Kh=4×10−10,[NH4Cl]=0.1 M
NH4Cl is a mixture of strong acid and weak base
we know the relation
Kh=KwKb
4×10−10=10−14Kb
Kb=2.5×10−5
pKb=−log Kb
=−log 2.5×10−5
=6−2×0.7
=4.6
Also, pH=12×(pKw−pKb−log c)
pH=12×(14−4.6−log 0.1)
pH=5.2