Question

A solution of acetic acid has a pH of 3.45. What is the concentration of acetic acid in this solution? Ka for CH3COOH is 1.8×10-5.

Answer 1

Answer:

0.007 M

Explanation:

pH is defined as the negative logarithm of the concentration of hydrogen ions.

Thus,  

pH = - log [H⁺]

The expression of the pH of the calculation of weak acid is:-

$pH=-log(\sqrt{k_a\times C})$

Where, C is the concentration = ?

Given, pH = 3.45

So, for $CH_3COOH$, $K_a=1.8\times 10^{-5}$

$3.45=-log(\sqrt{1.8\times 10^{-5}\times C})$

$\log _{10}\left(\sqrt{1.8\cdot \:10^{-5}C}\right)=-3.45$

C = 0.007 M