Enter the balanced equation for the ionization of butanoic acid, a carboxylic acid, in water.
The correct answer and explanation is:
Okay, here is the balanced equation for the ionization of butanoic acid in water, followed by an explanation.
Balanced Equation:
CH₃CH₂CH₂COOH (aq) + H₂O (l) ⇌ CH₃CH₂CH₂COO⁻ (aq) + H₃O⁺ (aq)
Explanation:
Butanoic acid (CH₃CH₂CH₂COOH) is a weak carboxylic acid. When it is dissolved in water, it undergoes a process called ionization, which is an acid-base reaction where the acid donates a proton (H⁺) to a water molecule. This reaction does not go to completion, which is characteristic of weak acids, and therefore an equilibrium is established between the reactants and products.
In the balanced equation, butanoic acid (CH₃CH₂CH₂COOH), shown in the aqueous state (aq), reacts with water (H₂O), shown as a liquid (l). Butanoic acid acts as a Brønsted-Lowry acid, donating its acidic proton, which is the hydrogen atom attached to the oxygen in the carboxyl (-COOH) group.
Water acts as a Brønsted-Lowry base in this reaction, accepting the proton from butanoic acid. When water accepts a proton, it forms the hydronium ion (H₃O⁺), which is also in the aqueous state (aq). The presence of hydronium ions is what makes the solution acidic.
When butanoic acid loses its proton, it forms its conjugate base, the butanoate ion (CH₃CH₂CH₂COO⁻). This ion carries a negative charge and is also dissolved in water (aq).
The double arrow (⇌) in the equation signifies that the reaction is reversible and exists in equilibrium. This means that while some butanoic acid molecules ionize to form butanoate ions and hydronium ions, the reverse reaction (butanoate ions reacting with hydronium ions to reform butanoic acid and water) also occurs simultaneously. At equilibrium, the rates of the forward and reverse reactions are equal, resulting in constant concentrations of all species involved. For a weak acid like butanoic acid, the equilibrium lies primarily to the left, indicating that only a small fraction of the butanoic acid molecules are ionized at any given time.