12.4.1 Expression for Ka

• The Ka value for a weak acid with equilibrium concentrations [H+] = [A-] = 0.01 M and [HA] = 0.09 M is 0.0011
• Weak acids dissociate completely in solution.

  False
• Steps in the dissociation of a weak acid in water:

  1️⃣ HA partially dissociates

  2️⃣ Forms H+ and A-

  3️⃣ Forward and reverse reactions reach equilibrium
• The general dissociation equation for a weak acid HA in water is HA(aq) ⇌ H⁺(aq) + A⁻(aq)
• An example of a strong acid is hydrochloric acid.
• What type of dissociation do weak acids undergo in solution?

  Partial dissociation
• An example of a weak acid is acetic acid.
• The dissociation of a weak acid in water results in equilibrium.
• The dissociation equation for a weak acid HA in water is HA(aq) ⇌ H⁺(aq) + A⁻(aq).
• Write the dissociation equation for acetic acid (CH₃COOH) in water.

  CH₃COOH(aq) ⇌ H⁺(aq) + CH₃COO⁻(aq)
• Weak acids partially dissociate to form hydrogen ions and their conjugate base.
• The expression for Ka is Ka = [H⁺][A⁻]/[HA].
• A higher Ka value indicates a stronger weak acid.
• Match the term with its definition:

  [H⁺] ↔️ Concentration of hydrogen ions

  [A⁻] ↔️ Concentration of conjugate base

  [HA] ↔️ Concentration of undissociated acid
• What does a higher Ka value indicate about a weak acid?

  Stronger weak acid
• The acid dissociation constant is denoted as Ka
• A higher Ka value means the acid dissociates more readily in water.
• What are the two key steps to calculate Ka?

  Determine equilibrium concentrations and plug into the Ka expression
• The Ka quantifies the ratio of products to reactants at equilibrium
• The acid dissociation constant (Ka) measures the extent to which a weak acid dissociates in solution
• A higher Ka value indicates a stronger weak acid.
• What is the expression for Ka in terms of equilibrium concentrations?

  Ka = \frac{[H^+][A^-]}{[HA]}</latex>
• [H+] refers to the concentration of hydrogen ions
• Match the term with its definition:

  [H+] ↔️ Concentration of hydrogen ions

  [A-] ↔️ Concentration of conjugate base

  [HA] ↔️ Concentration of undissociated weak acid
• What is the Ka value if [H+] = 0.01 M, [A-] = 0.01 M, and [HA] = 0.09 M?

  0.0011
• The acid dissociation constant is denoted as Ka
• What does the term Ka quantify in the context of acid dissociation?

  Ratio of products to reactants
• A higher Ka value indicates that the weak acid dissociates more readily in water.
• Steps to calculate the acid dissociation constant (Ka) for a weak acid:

  1️⃣ Determine the equilibrium concentrations of H+, A-, and HA.

  2️⃣ Plug these values into the Ka expression.

  3️⃣ Solve for Ka.
• What is the Ka value if [H+] = 0.01 M, [A-] = 0.01 M, and [HA] = 0.09 M?

  0.0011