Many compounds are only partially dissociated into ions in aqueous solution. Trichloroacetic acid (CCl₃CO₂H), for instance, is partially dissociated in water according to the equationCCl₃CO₂H (aq) → H⁺ (aq) + CCl₃CO₂⁻ (aq)For a solution prepared by dissolving 1.00 mol of trichloroacetic acid in 1.00 kg of water, 36.0% of the trichloroacetic acid dissociates to form H⁺ and CCl₃CO₂⁻ ions.What is the total concentration of dissolved ions and molecules in 1 kg of water?

Verified step by step guidance

1. Identify the initial amount of trichloroacetic acid: 1.00 mol.
2. Calculate the amount of trichloroacetic acid that dissociates: 36.0% of 1.00 mol.
3. Determine the moles of H⁺ and CCl₃CO₂⁻ ions formed, which is equal to the moles of dissociated trichloroacetic acid.
4. Calculate the moles of undissociated trichloroacetic acid remaining: 1.00 mol - moles dissociated.
5. Add the moles of undissociated trichloroacetic acid and the moles of ions to find the total concentration of dissolved species.

Key Concepts

Dissociation of Acids

Dissociation refers to the process by which an acid separates into its constituent ions in solution. For weak acids like trichloroacetic acid, this process is not complete, meaning only a fraction of the acid molecules release protons (H⁺) and form anions. Understanding the degree of dissociation is crucial for calculating the concentrations of ions in solution.

Concentration Calculations

Concentration is a measure of the amount of a substance in a given volume of solution, typically expressed in moles per liter (M). To find the total concentration of dissolved species, one must account for both the undissociated acid and the ions produced from dissociation. This involves using the initial amount of acid and the percentage that dissociates to determine the final concentrations.

Molarity and Solution Composition

Molarity (M) is defined as the number of moles of solute per liter of solution. In this context, the total concentration of dissolved ions and molecules includes both the dissociated ions and the undissociated acid. To calculate this, one must convert the mass of water into liters and then sum the contributions from all species present in the solution.