When 0.050 mol of NaOH is added to 0.100 mol of an unknown weak acid, the pH was found to be 4.2 . Which of the following can be the acid?
A) Chlorous acid Ka =1×10⁻²
(B) Nitrous acid Ka =4×10⁻⁴
(C) Benzoic acid Ka =6×10⁻⁵
(D) Hypochlorous acid Ka=4×10⁻⁸