40 ml of \( CH _{3} COOH \) solution is mixed with V ml of \( 0.4 M - NaOH \) solution. If the pH of resulting solution at equivalence point is 9.0 , the initial concentration of \( CH _{3} COOH \) solution is [ \( K _{a} \) of \( CH _{3} COOH =2 \times 10^{-5} \), \( \log 2=0.30 \) ]
