Calculate the pH and the concentrations of the other species...

Calculate the $\mathrm{pH}$ and the concentrations of the other species in a $0.10-\mathrm{M}$ aqueous solution of chloroacetic acid, $\mathrm{ClCH}_{2} \mathrm{COOH}(a q)$, given that $K_{\mathrm{a}}=$ $1.4 \times 10^{-5} \mathrm{M}$ at $25^{\circ} \mathrm{C}$

Key Concepts

pH Calculation

pH calculation involves determining the hydrogen ion concentration in a solution and then using the definition of pH, which is the negative logarithm (base 10) of the hydrogen ion concentration. In the context of weak acid solutions, once the equilibrium concentration of hydrogen ions is estimated, the pH can be directly calculated, providing an important measure of the solution's acidity.

ICE Table Method

The ICE table (Initial, Change, Equilibrium) is a systematic tool used to organize and solve equilibrium problems for reactions, including those involving weak acids and bases. It helps in visualizing the initial concentrations, the changes that occur as the reaction proceeds, and the final equilibrium concentrations of all species involved. This method is particularly useful when dealing with the small extent of dissociation in weak acids.

Weak Acid Equilibrium

Weak acid equilibrium refers to the reversible reaction where a weak acid dissociates partially in water to produce hydrogen ions and its conjugate base. Unlike strong acids, which dissociate completely, weak acids establish an equilibrium between the undissociated molecules, the hydrogen ions, and the conjugate base. Understanding this equilibrium is crucial for calculating pH and the concentrations of all species present in the solution.

Acid Dissociation Constant (Ka)

The acid dissociation constant, Ka, is a quantitative measure of the strength of a weak acid in solution. It indicates the extent to which an acid dissociates into its conjugate base and hydrogen ions. A higher Ka value corresponds to a stronger acid, while a lower Ka value indicates a weaker acid. In the context of weak acid equilibria, Ka is essential for setting up the equilibrium expression that governs the concentrations of all species in solution.

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