Question

Propanoic acid is a weak acid used to inhibit mould formation in bread. A 0.10 mol/L solution of propanoic acid has a pH of 2.96. Calculate the Ka for the propanoic acid.

Answer 1

Answer to Question #58553, Chemistry / Other

Propanoic acid is a weak acid used to inhibit mould formation in bread. A 0.10 mol/L solution of propanoic acid has a pH of 2.96. Calculate the Ka for the propanoic acid.

Solution:

$$K_a = \frac{[H^+][A^-]}{[HA]}$$ $$[H^+] = [A^-]$$ $$K_a = \frac{[H^+]^2}{[HA]} = \frac{(10^{-pH})^2}{c - 10^{-pH}} = \frac{0.0011^2}{0.1 - 0.0011} = 1.2 \times 10^{-5}$$

Answer:

$$1.2 \times 10^{-5}$$

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