Question

What is the pH of a 1 M $C{H}_{3}COOH$ solution?

[$K_a$ of acetic acid$=1.8\times {10}^{-5},K_w={10}^{-14}mo{l}^{2}litr{e}^{-2}$]

• A. 9.4
• B. 4.8
• C. 3.6
• D. 2.4

Answer 1

The correct option is D 2.4

$C{H}_{3}COOH\leftrightarrows C{H}_{3}CO{O}^{-}+H^{+}$

For weak acid $C{H}_{3}COOH$, by applying ostwald's dilution law equation,
$\left[H^{+}\right]=\sqrt{(C\times K_a)}$

By substituting values in the above equation, we get,
$\left[H^{+}\right]=\sqrt{(1\times 1.8\times {10}^{-5})}=0.004243M$

The pH is negative logarithm of hydrogen ion concentration.
$pH=-log\left[H^{+}\right]=-log\left(0.004243\right)=2.4$.

Option D is correct.