20 cc of ‘x’ M HCl is exactly neutralised by 40 cc of 0.05 M NaOH. The pH of HCl solution is

Equivalents of HCl = Equivalents of NaOH

⇒ 20 x10^-3 x              = 40 x 10^-3 x0.05

⇒ x = 0.1

$$\begin{gathered} \left[{\mathrm{H}}^{+}\right]={10}^{-1} \\ \therefore {\mathrm{P}}^{\mathrm{H}}=1 \end{gathered}$$