Answer : The concentration of benzoic acid in this solution was, 0.149 M
Explanation :
The balanced equilibrium reaction will be,
[tex]C_6H_5COOH\rightleftharpoons C_6H_5COO^-+H^+[/tex]
initially conc. c 0 0
At eqm. c(1-α) cα cα
The expression for dissociation constant is:
[tex]k_a=\frac{c\alpha\times c\alpha}{c(1-\alpha)}[/tex]
when α is very very small the, the expression will be,
[tex]k_a=\frac{c^2\alpha^2}{c}=c\alpha^2[/tex]
Given:
α = 2.05 % = 0.0205
[tex]K_a=6.3\times 10^{-5}[/tex]
Now put all the given values in this expression, we get:
[tex]6.3\times 10^{-5}=c\times (0.0205)^2[/tex]
c = 0.149 M
Therefore, the concentration of benzoic acid in this solution was, 0.149 M
