Chapter 7. Solutions and Concentration

A solution has a solvent and one or more solutes. “Like dissolves like”: polar solvents dissolve polar and ionic solutes.

Concentration units

Molarity (M) = mol solute / L solution

Molality (m) = mol solute / kg solvent

Mass percent = (mass solute / mass solution) × 100

Mole fraction χ = nᵢ / n_total

Dilution: M₁V₁ = M₂V₂.

Colligative properties depend on the number of dissolved particles: vapor-pressure lowering (Raoult’s law), boiling-point elevation (ΔT_b = iK_b m), freezing-point depression (ΔT_f = iK_f m) and osmotic pressure (Π = iMRT) [2][3].

Solubility rules (common): nitrates and Group 1 salts are soluble; most carbonates and hydroxides are insoluble except those of Group 1.

Review: Prepare 250 mL of 0.100 M NaCl. What mass of NaCl is needed? (1.46 g.)