Solutions in Chemistry: A Brief Overview
Solutions are homogeneous mixtures of two or more substances. They consist of a solute (the substance present in a smaller amount) and a solvent (the substance present in a larger amount).
Types of Solutions
- Gaseous solutions: Examples include air (a mixture of gases) and helium in oxygen.
- Liquid solutions: Most common type. Examples include salt water, sugar water, and alcohol in water.
- Solid solutions: Examples include alloys (like brass or steel) and carbon in iron (steel).
Factors Affecting Solubility
- Temperature: Generally, solubility increases with temperature for solids and liquids in liquids. However, for gases in liquids, solubility decreases with increasing temperature.
- Pressure: For gases in liquids, solubility increases with increasing pressure (Henry's law).
- Nature of solute and solvent: Polar substances tend to dissolve in polar solvents, while nonpolar substances dissolve in nonpolar solvents (like dissolves like).
Concentration of Solutions
- Molarity (M): Moles of solute per liter of solution.
- Molality (m): Moles of solute per kilogram of solvent.
- Mass percentage (%): Mass of solute divided by mass of solution, multiplied by 100.
- Volume percentage (%v/v): Volume of solute divided by volume of solution, multiplied by 100.
- Parts per million (ppm): Mass of solute per million parts of solution.
- Parts per billion (ppb): Mass of solute per billion parts of solution.
Properties of Solutions
- Colligative properties: Depend on the number of solute particles, not the nature of the solute. Examples include boiling point elevation, freezing point depression, osmotic pressure, and vapor pressure lowering.
- Ideal solutions: Solutions that obey Raoult's law (the vapor pressure of a component in a solution is proportional to its mole fraction).
