Question

\Lambdaqucous solution of acctic acid contains (1) \(\mathrm{CII}_{3} \mathrm{COOII}, \mathrm{II}^{+}\) (2) \(\mathrm{CII}_{3} \mathrm{COO}^{-}, \mathrm{II}_{3} \mathrm{O}^{-}, \mathrm{CH}_{3} \mathrm{COOH}\) (3) \(\mathrm{CII}_{3} \mathrm{COO}^{-}, \mathrm{II}_{3} \mathrm{O}^{-}, \mathrm{II}^{+}\) (4) \(\mathrm{CII}_{3} \mathrm{COOII}, \mathrm{CII}_{3} \mathrm{COO}^{-}, \mathrm{II}^{+}\)

Short answer

Option 4 is correct: \(\text{CH}_3 \text{COOH}, \text{CH}_3 \text{COO}^-, \text{H}^+\).

Step-by-step solution

Understand the Question

Determine which species are present in an aqueous solution of acetic acid.

Write the Chemical Dissociation Equation

The dissociation of acetic acid \(\text{CH}_3 \text{COOH}\) in water can be described by the equilibrium equation: \(\text{CH}_3 \text{COOH} \rightleftharpoons \text{CH}_3 \text{COO}^- + \text{H}^+\).

Identify the Species in Solution

From the dissociation equation, the species present in solution are acetic acid (\(\text{CH}_3 \text{COOH}\)), acetate ion (\(\text{CH}_3 \text{COO}^-\)), and proton (\(\text{H}^+\)). Water (\(\text{H}_2 \text{O}\)) is also present because the solution is aqueous.

Evaluate the Given Options

Compare the identified species with the given options: 1. \(\text{CH}_3 \text{COOH}, \text{H}^+\) – missing acetate ion. 2. \(\text{CH}_3 \text{COO}^-, \text{H}_2 \text{O}^-, \text{CH}_3 \text{COOH}\) – has incorrect \text{H}_2 \text{O}^{-}\ ion. 3. \(\text{CH}_3 \text{COO}^-, \text{H}_2 \text{O}, \text{H}^+\) – includes water incorrectly as hydroxide ion. 4. \(\text{CH}_3 \text{COOH}, \text{CH}_3 \text{COO}^-, \text{H}^+\) – all correct.

Key concepts

Chemical Equilibrium

In chemistry, equilibrium refers to the state where the concentrations of reactants and products remain constant over time because the forward and reverse reactions occur at the same rate. In the dissociation of acetic acid, this concept is crucial. When \text{CH}_3 \text{COOH} (acetic acid) dissolves in water, it establishes an equilibrium with its ions (\text{CH}_3 \text{COO}^- and \text{H}^+).
The chemical equation representing this process is:
\( \text{CH}_3 \text{COOH} \rightleftharpoons \text{CH}_3 \text{COO}^- + \text{H}^+ \)
This equation highlights that at equilibrium, the concentration of \text{CH}_3 \text{COOH}, \text{CH}_3 \text{COO}^-, and \text{H}^+ remains constant.

Key points to remember about chemical equilibrium in this context include:

• Reaction rates: Forward and backward reactions occur at the same rate.
• Constant concentrations: The amount of each species stays unchanged at equilibrium.

Aqueous Solutions

Aqueous solutions are solutions where water is the solvent. In these solutions, substances (solutes) dissolve in water to form a uniform mixture. Acetic acid is an example of a substance that can dissolve in water to form an aqueous solution.
When acetic acid, \text{CH}_3 \text{COOH}, dissolves in water, it dissociates into acetate ions (\text{CH}_3 \text{COO}^-) and hydrogen ions (\text{H}^+). This process can be represented by the equation:
\( \text{CH}_3 \text{COOH} + \text{H}_2 \text{O} \rightarrow \text{CH}_3 \text{COO}^- + \text{H}^+ \)
In the context of aqueous solutions, it’s important to remember:

• Water molecules interact with solutes, stabilizing the ions in the solution.
• Aqueous solutions support various chemical reactions due to the solvent properties of water.

Acid-Base Chemistry

Acid-base chemistry studies the behavior of acids and bases in solutions and their reactions with each other. According to the Brønsted-Lowry theory, an acid is a proton donor, and a base is a proton acceptor. Acetic acid (\text{CH}_3 \text{COOH}) is a weak acid that partially ionizes in water:
\( \text{CH}_3 \text{COOH} \rightleftharpoons \text{CH}_3 \text{COO}^- + \text{H}^+ \)
In this reaction:

• Acetic acid (\text{CH}_3 \text{COOH}) donates a proton (\text{H}^+).
• The acetate ion (\text{CH}_3 \text{COO}^-) is the conjugate base.
• The hydrogen ion (\text{H}^+) is released into the solution.

Understanding acid-base reactions involves concepts such as dissociation, pH, and equilibrium. Remember that the strength of an acid depends on its ability to donate protons and that weak acids like acetic acid do not completely dissociate in water.