Question

Calculate the pH at the equivalence point during the titration of `0.1M, 25 mL CH_(3)COOH` with `0.05M NaOH` solution. `[K_(a)(CH_(3)COOH) = 1.8 xx 10^(-5)]`
A. `9.63`
B. `8.63`
C. `10.63`
D. `11.63`

Answer 1

Correct Answer - B
Since, at equivalence point
`N_(1)V_(1) = N_(2)V_(2)`
(for acid) (for base)
`:.` Volume of `NaOH` required to reach equivalence point
`= (0.1 xx 25)/(0.05) = 50mL`
`:.` Concentration of salt formed `=("Millimolars of acid")/("Total volume in mL")`
`= (25 xx 0.1)/(75) = (0.1)/(3)`
Since, `[H^(+)] = sqrt((K_(w)xx K_(a))/(C)) = sqrt((10^(-14) xx 1.8 xx 10^(-5)xx 3)/(0.1))`
`:. pH = 8.63`