upgrade

💏intro to chemistry review

Ion Product

Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025

Definition

The ion product, denoted as Q or Qc, is a quantitative measure of the extent of a chemical reaction or the degree of dissociation of a weak electrolyte in a solution. It represents the product of the concentrations of the ions involved in the reaction, raised to their respective stoichiometric coefficients. The ion product is a crucial concept in understanding the concepts of pH and pOH.

Pep mascot

5 Must Know Facts For Your Next Test

  1. The ion product is calculated by multiplying the concentrations of the ions involved in the reaction, raised to their respective stoichiometric coefficients.
  2. The ion product is compared to the equilibrium constant (K) or the solubility product constant (Ksp) to determine the direction of a reaction or the solubility of a compound.
  3. If the ion product (Q) is less than the equilibrium constant (K), the reaction will proceed in the forward direction to reach equilibrium.
  4. If the ion product (Q) is greater than the equilibrium constant (K), the reaction will proceed in the reverse direction to reach equilibrium.
  5. The ion product is a key concept in understanding the pH and pOH of a solution, as it is related to the concentration of hydrogen ions (H+) and hydroxide ions (OH-).

Review Questions

  • Explain the relationship between the ion product (Q) and the equilibrium constant (K) in determining the direction of a reaction.
    • The relationship between the ion product (Q) and the equilibrium constant (K) determines the direction a reaction will proceed to reach equilibrium. If the ion product (Q) is less than the equilibrium constant (K), the reaction will proceed in the forward direction to increase the concentrations of the products and reach equilibrium. Conversely, if the ion product (Q) is greater than the equilibrium constant (K), the reaction will proceed in the reverse direction to decrease the concentrations of the products and reach equilibrium.
  • Describe how the ion product (Q) is related to the pH and pOH of a solution.
    • The ion product (Q) is directly related to the concentrations of hydrogen ions (H+) and hydroxide ions (OH-) in a solution, which are used to calculate the pH and pOH, respectively. The pH is defined as the negative logarithm of the hydrogen ion concentration, while the pOH is the negative logarithm of the hydroxide ion concentration. The ion product (Q) represents the product of the concentrations of these ions, and its relationship to the equilibrium constant (K) or the solubility product constant (Ksp) determines the acidity or basicity of the solution, as reflected in the pH and pOH values.
  • Analyze the significance of the ion product (Q) in the context of solubility equilibria.
    • In the context of solubility equilibria, the ion product (Q) is compared to the solubility product constant (Ksp) to determine the solubility of a slightly soluble salt. If the ion product (Q) is less than the solubility product constant (Ksp), the solution is unsaturated, and the salt will continue to dissolve. If the ion product (Q) is greater than the solubility product constant (Ksp), the solution is supersaturated, and the salt will precipitate out of the solution. The ion product (Q) is a crucial factor in understanding the solubility of compounds and predicting the direction of precipitation or dissolution reactions.