The pH of the mixture of 25ml of 0.01M of $C{H}_{3}COOH$ ($K_a$ of $C{H}_{3}COOH$ = $5\times {10}^{-5}$ and 25ml of 0.01M of NaOH solution is ______.

pH = 7 + $\frac{1}{2}[p{K}_a+logc]$

$C{H}_{3}COOH+NaOH\rightleftharpoons :$$C{H}_{3}COONa$ + $H_{2}O$

Total volume of $C{H}_{3}COONa$ = 25+25 = 50ml

Concentration of $C{H}_{3}COONa$ (c) = $\frac{0.01\times 25}{50}$ = $5\times {10}^{-3}$

pH = 7 + $\frac{1}{2}$[$p{K}_a$ + log c]

= 7 + $\frac{1}{2}$[$-log{K}_a$ + log c]

= 7 + 0.5($-log5\times {10}^{-5})$ + $log5\times {10}^{-3}$)

= 7 + 1 = 8.

Hence, the answer is 8.