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Calculating the pH of a Weak Acid

Weak acids only partially dissociate in aqueous solution.CH3COOH(aq) ⇌ H+(aq) + CH3COO-(aq).In general for a weak acid HAHA(aq) ⇌ H+ + A-(A stands for anion). This means that the acid dissociation constant at equilibrium is equal to[H+] = [A-] as they both originated from the same moleculeGiven that pH = -log10[H+], the pH of a weak acid is given by

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Specification: OCR Chemistry A (H432), A-level, 5.1.3 Acids, bases and buffers. Topic: Acids, Bases and Buffers.

Key terms in this lesson

pH
A measure of the hydrogen ion concentration of a solution, defined as pH = -log10[H+].
weak acid
An acid that only partially dissociates into its ions in aqueous solution.
acid dissociation constant Ka
The equilibrium constant for the dissociation of a weak acid in aqueous solution.

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