Write the expression for the ion product constant for water, K_w.

Verified step by step guidance

1. Understand that the ion product constant for water, denoted as \( K_w \), is a special equilibrium constant for the self-ionization of water.
2. Recognize the self-ionization reaction of water: \( 2H_2O(l) \rightleftharpoons H_3O^+(aq) + OH^-(aq) \).
3. Simplify the reaction to: \( H_2O(l) \rightleftharpoons H^+(aq) + OH^-(aq) \), where \( H^+ \) is often used interchangeably with \( H_3O^+ \).
4. Write the expression for the equilibrium constant \( K_w \) as the product of the concentrations of the ions: \( K_w = [H^+][OH^-] \).
5. Note that \( K_w \) is temperature-dependent and at 25°C, \( K_w \) is typically \( 1.0 \times 10^{-14} \).

Key Concepts

Ion Product Constant for Water (Kw)

The ion product constant for water, denoted as Kw, is the equilibrium constant for the self-ionization of water. It is defined as the product of the concentrations of hydrogen ions [H+] and hydroxide ions [OH-] in pure water at a given temperature. At 25°C, Kw is equal to 1.0 x 10^-14, indicating that the concentrations of H+ and OH- are both 1.0 x 10^-7 M in neutral water.

Self-Ionization of Water

Self-ionization of water refers to the process where two water molecules react to form one hydronium ion (H3O+) and one hydroxide ion (OH-). This reaction is represented by the equation: 2 H2O ⇌ H3O+ + OH-. This equilibrium is crucial for understanding acid-base chemistry, as it establishes the basis for the pH scale and the behavior of acids and bases in aqueous solutions.

Acid-Base Equilibrium

Acid-base equilibrium involves the balance between acids and bases in a solution, which is influenced by the concentrations of H+ and OH- ions. The pH scale, which ranges from 0 to 14, is a logarithmic scale that measures the acidity or basicity of a solution based on the concentration of H+. Understanding this equilibrium is essential for predicting how substances will behave in solution and for calculating pH and pOH.