Chemistry Solutions Overview

Study Notes

Introduction

The term "solution" in chemistry refers to a homogeneous mixture of two or more substances.
Homogeneity means the composition of the solution is uniform throughout.
Solutions are characterized by their solute and solvent components.

Solute and Solvent

The solute is the substance being dissolved.
The solvent is the substance doing the dissolving.
Typically, the solvent is present in a larger amount than the solute.
Solute and solvent can be solids, liquids, or gases.

Types of Solutions

Solid solutions: A solid dissolved in another solid (e.g., alloys).
Liquid solutions: A liquid dissolved in another liquid (e.g., salt water).
Gaseous solutions: A gas dissolved in another gas (e.g., air).
- Air is a gaseous solution containing nitrogen, oxygen, and other trace gases.
Solid in liquid: A solid dissolved in a liquid (e.g., sugar dissolved in water).
Gas in liquid: A gas dissolved in a liquid (e.g., carbon dioxide in soda).

Solubility

Solubility is the ability of a substance to dissolve in a solvent.
Solubility is often expressed as the mass of solute that can dissolve in a given amount of solvent at a particular temperature and pressure.
Solubility depends on several factors, including temperature and pressure.
- Generally, solubility increases with temperature for solid solutes in liquids.
- But not always, in some cases, solubility decreases with temperature.
- Solubility of gases in liquids decreases with increasing temperature.
- Increasing pressure increases the solubility of gases in liquids.

Factors Affecting Solution Formation

Nature of solute and solvent: "Like dissolves like" is a general guideline. Polar solvents dissolve polar solutes, and nonpolar solvents dissolve nonpolar solutes.
Temperature: As mentioned above, temperature affects solubility.
Pressure: As mentioned above, pressure significantly affects the solubility of gases in liquids.
Surface area: Increasing the surface area of the solute increases the rate of dissolution.
Agitation: Stirring or shaking a solution increases the rate of dissolution.
Presence of other solutes: Other solutes can sometimes affect the solubility of a given solute.

Concentration

Concentration describes the amount of solute dissolved in a given amount of solvent or solution.
Common units include molarity, molality, and percent by mass.
Molarity (M) is moles of solute per liter of solution.
Molality (m) is moles of solute per kilogram of solvent.
Percent by mass (% w/w) is the mass of solute divided by the mass of solution, multiplied by 100.

Solution Properties

Solutions exhibit properties different from those of the pure solvent.
These are called colligative properties, depending on the number of solute particles rather than the identity of the solute.
These include:
- Vapor pressure lowering
- Boiling point elevation
- Freezing point depression
- Osmotic pressure

Unsaturated Solution

A solution that has less solute dissolved than its maximum solubility. More solute can be dissolved into the solvent

Saturated Solution

A solution that has the maximum amount of solute dissolved at a given temperature and pressure. No more solute can be dissolved in the solution at this temperature and pressure.

Supersaturated Solution

A solution that has more solute dissolved than its maximum solubility. This is a non-equilibrium state, and the excess solute is unstable.

Miscible and Immiscible Liquids

Miscible liquids completely dissolve into each other in any proportion (e.g., ethanol and water).
Immiscible liquids do not dissolve in each other, and separate into distinct layers (e.g., oil and water).

Description

This quiz explores the concept of solutions in chemistry, focusing on the definitions of solute and solvent, and the various types of solutions. Understand the differences between solid, liquid, and gaseous solutions, and learn how these components interact within mixtures.