Calculate the pH of a 0.1 M solution of acetic acid — JEE Chemistry
Calculate the pH of a $0.1$ M solution of acetic acid. ($K_a = 1.8 \times 10^{-5}$)
1 Answer
VAVidaara Admin
✓ Vidaara Team
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· 14d ago
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$$CH_3COOH \rightleftharpoons CH_3COO^- + H^+$$
$$K_a = \frac{x^2}{0.1 - x} \approx \frac{x^2}{0.1}$$
$$x^2 = 1.8\times10^{-5} \times 0.1 = 1.8\times10^{-6}$$
$$x = [H^+] = 1.342\times10^{-3} M$$
$$pH = -\log(1.342\times10^{-3}) = 2.87$$
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Discussion (3)
MT
For revision — the key formula used here comes up almost every year.
PI
How do we know the approximation is valid here?
C
Brilliant explanation, the substitution step is what I kept missing.