Write chemical equations and corresponding equilibrium expressions for each of the two ionization steps of carbonic acid.

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Identify the chemical formula for carbonic acid, which is \( \text{H}_2\text{CO}_3 \).

Write the chemical equation for the first ionization step: \( \text{H}_2\text{CO}_3 (aq) \rightleftharpoons \text{H}^+ (aq) + \text{HCO}_3^- (aq) \).

Write the equilibrium expression for the first ionization step: \( K_{a1} = \frac{[\text{H}^+][\text{HCO}_3^-]}{[\text{H}_2\text{CO}_3]} \).

Write the chemical equation for the second ionization step: \( \text{HCO}_3^- (aq) \rightleftharpoons \text{H}^+ (aq) + \text{CO}_3^{2-} (aq) \).

Write the equilibrium expression for the second ionization step: \( K_{a2} = \frac{[\text{H}^+][\text{CO}_3^{2-}]}{[\text{HCO}_3^-]} \).

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Ionization of Acids

Ionization refers to the process by which an acid donates protons (H⁺ ions) to water, forming hydronium ions (H₃O⁺). Carbonic acid (H₂CO₃) undergoes two ionization steps, first losing one proton to form bicarbonate (HCO₃⁻), and then losing a second proton to form carbonate (CO₃²⁻). Understanding this process is crucial for writing the correct chemical equations.

Chemical Equilibrium

Chemical equilibrium occurs when the rates of the forward and reverse reactions are equal, resulting in constant concentrations of reactants and products. For the ionization of carbonic acid, the equilibrium expressions can be derived from the concentrations of the species involved in each step, reflecting the balance between the acid and its ions.

Equilibrium Expressions

Equilibrium expressions are mathematical representations of the concentrations of products and reactants at equilibrium, typically written in the form K = [products]/[reactants]. For carbonic acid, the equilibrium constants for its two ionization steps can be expressed as K₁ for the first ionization to bicarbonate and K₂ for the second ionization to carbonate, highlighting the relationship between the concentrations of the species involved.

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