Question

Determine pH of 0.165 M NH4Cl

Answer 1

ammonium chloride is a weak acid, so you'd use: for weak acids use
pH = 1/2(pKa - log(c_acid) )
\[pH = \frac{ 1 }{ 2 }(pKa-\log(C_{acid}))\]
where C = conjugate acid.