Answer :
Answer:
The pH at 25°C of 0.33M solution is 5.36.
Explanation:
Let us calculate -:
[tex]NaC_6H_5CO_2$\rightarrow$ salt of weak acid + sodium benzoate[/tex]
pH of salt of weak acid and sodium benzoate is given by-
pH =[tex]7+\frac{1}{2}pk_a+\frac{1}{2}log (concentration of salt)[/tex]
concentration of salt = 0.33M
[tex]pK_a=4.2[/tex]
[tex]pH = 7 +\frac{4.2}{2} +\frac{1}{2}log (0.33)[/tex]
[tex]pH=7 +\frac{4.2}{2} + \frac{(-0.4815)}{2}[/tex]
pH = 5.36
Hence , the answer is 5.36