Chapter 14: Solutions
14.1: The Dissolving Process
- Heterogeneous Mixture
- A mixture with two or more distinct regions, giving it a nonuniform appearance.
- Homogeneous Mixture
- A mixture with only one phase, giving it a uniform appearance.
- Solution
- A homogeneous mixture of variable composition in a single phase.
- Solvent
- The most abundant substance in a solution, which dissolves the solute.
- Solute
- The substance dissolved by the solvent; typically in lower abundance.
Properties of Solutions
- Solutes cannot be filtered out.
- Solutes do not settle out over time.
- Solutions are uniform throughout.
- Components are not chemically combined.
- Solutions can have variable concentrations.
Types of Solutions
- Liquid Solutions
- Solvent: Liquid. Can dissolve solids, liquids, and gases. Includes miscibility (two liquids dissolve) and immiscibility (two liquids do not dissolve).
- Solid Solutions
- Solvent: Solid. Example: Metal alloys (e.g., steel).
- Gaseous Solutions
- Solvent: Gas. Example: Air (gaseous solutes dissolved in gaseous solvent).
The Dissolving Process (Liquid Solutions)
- Solvation
- The process by which solvent particles surround and separate solute particles.
- Hydration
- Solvation when the solvent is water.
- Dissociation
- Ionic compounds form ions when dissolved.
- Ionization
- Covalent compounds form ions when dissolved.
Steps of Solvation
- Endothermic Step
- Solvent absorbs thermal energy to overcome intermolecular forces.
- Exothermic Step
- Solvent and solute mix, releasing energy to form a stable arrangement.
- Enthalpy of Solution (ΔH)
- The net energy change during the dissolving process (measured in kJ/mol).
Factors Affecting the Dissolving Rate
- Temperature
- Stirring or agitation
- Surface area of the solute exposed to the solvent
Questions for Students
- Define heterogeneous mixture and homogeneous mixture. Provide examples.
- What are the key properties of solutions?
- Differentiate between miscibility and immiscibility.
- What are the steps involved in solvation? Explain using examples.
- How does temperature affect the rate of dissolving?