By adding 20 ml 0.1 N HCl to 20 ml 0.1 N KOH the $ P^H $ of obtained solution will be :
When equal volumes and concentrations of a strong acid (HCl) and a strong base (KOH) are mixed, they neutralize each other completely. The reaction is: $$ HCl + KOH ightarrow KCl + H_2O $$ Since they neutralize each other, the resulting solution is neutral, meaning the pH will be 7 at 25°C. Hence, the correct answer is 7.