Chemistry: Solubility and Intermolecular Forces

Study Notes

Definition: The ability of a substance to dissolve in a solvent to form a homogeneous mixture
Factors affecting solubility:
- Temperature: Increasing temperature generally increases solubility
- Pressure: Increasing pressure generally increases solubility
- Polarity: Polar solvents dissolve polar solutes, non-polar solvents dissolve non-polar solutes
- Molecular size and shape: Smaller molecules are more soluble than larger ones
Types of solubility:
- Miscible: Two liquids that can mix in any proportion (e.g., water and ethanol)
- Immiscible: Two liquids that cannot mix (e.g., oil and water)
- Partially miscible: Two liquids that can mix in limited proportions (e.g., phenol and water)

Definition: Weak forces between molecules that hold them together in a substance
Types of intermolecular forces:
- London dispersion forces: Weak forces between non-polar molecules (e.g., methane, CH₄)
- Dipole-dipole forces: Forces between polar molecules with permanent dipoles (e.g., water, H₂O)
- Hydrogen bonding: Strong forces between molecules with hydrogen bonded to a highly electronegative atom (e.g., water, ammonia)
- Ion-dipole forces: Forces between ions and polar molecules (e.g., sodium chloride, NaCl)
Strength of intermolecular forces:
- London dispersion forces < dipole-dipole forces < hydrogen bonding < ion-dipole forces
Effects of intermolecular forces:
- Boiling point: Higher boiling point indicates stronger intermolecular forces
- Melting point: Higher melting point indicates stronger intermolecular forces
- Viscosity: Thicker, more viscous liquids have stronger intermolecular forces