• The solvent is a gas, and the solute can be a gas, liquid, or solid.

• Examples:

• Gas in Gas: Air (oxygen and nitrogen).

• Liquid in Gas: Water vapor in air (humidity).

• Solid in Gas: Camphor vapor in air.

• The solvent is a liquid, and the solute can be a gas, liquid, or solid.

• Examples:

• Gas in Liquid: Carbonated drinks (CO₂ dissolved in water).

• Liquid in Liquid: Alcohol in water (ethanol-water solution).

• Solid in Liquid: Salt in water (NaCl solution).

• The solvent is a solid, and the solute can be a gas, liquid, or solid.

• Examples:

• Gas in Solid: Hydrogen in palladium (used for hydrogen storage).

• Liquid in Solid: Mercury in silver (dental amalgam).

• Solid in Solid: Alloys like brass (copper and zinc) or steel (iron and carbon).

Expression of Concentration of Solutions of Solids in Liquids

The concentration of a solution refers to the amount of solute present in a given quantity of solvent or solution. It can be expressed in various ways, depending on the requirements of a particular application.

Different Ways to Express Concentration

• Mass Percentage (% w/w):
  Mass % = (Mass of solute / Mass of solution) × 100

  It represents the mass of solute in 100 grams of solution.

• Volume Percentage (% v/v):
  Volume % = (Volume of solute / Volume of solution) × 100

  It is used when both solute and solvent are liquids.

• Mass by Volume Percentage (% w/v):
  Mass/Volume % = (Mass of solute in grams / Volume of solution in mL) × 100

  Commonly used in medical and pharmaceutical applications.

• Molarity (M):
  M = Moles of solute / Volume of solution in liters

  Expresses concentration in terms of moles of solute per liter of solution.

• Molality (m):
  m = Moles of solute / Mass of solvent in kg

  Used when temperature variations affect the solution volume.

• Normality (N):
  N = Number of gram equivalents of solute / Volume of solution in liters

  It depends on the type of reaction and is used in acid-base and redox reactions.

• Parts per Million (ppm):
  ppm = (Mass of solute / Mass of solution) × 10⁶

  Used for very dilute solutions, such as pollutants in air or water.

• Parts per Billion (ppb):
  ppb = (Mass of solute / Mass of solution) × 10⁹

  Used for extremely low concentrations, such as contaminants in drinking water.

• Mole Fraction (χ):
  χ_A = n_A / (n_A + n_B)

  Where n_A and n_B are the moles of solute and solvent, respectively.