ORG CHEM POST DISCUSSION

• Solubility


  Substances with similar polarities tend to be soluble in one another ("like dissolves like")
• Nonpolar substances


  Generally more soluble in nonpolar solvents
• Polar and ionic substances


  Generally more soluble in polar solvents
• Solubility Test


  1. Compound added

  2. Observation

  3. Explanation
• Naphthalene with water

  • Insoluble, forms a suspension
  • Naphthalene is nonpolar and doesn't dissolve in polar water, forming a suspension
• Urea with water

  • Soluble, dissolves completely
  • Urea is polar and dissolves in polar water, forming a clear solution
• NaNO3 with water

  • Soluble, dissolves completely
  • NaNO3 is polar and dissolves in polar water, forming a clear solution
• Naphthalene with petroleum ether

  • Soluble, dissolves in petroleum ether
  • Naphthalene is nonpolar and dissolves in nonpolar solvents like petroleum ether
• Urea with petroleum ether

  • Insoluble, does not dissolve in petroleum ether
  • Urea is polar and generally does not dissolve well in nonpolar solvents
• Boiling Point


  The temperature at which the vapour pressure of the liquid is equal to the atmospheric pressure. At boiling point, liquid changes from its liquid state to the gaseous state.
• Normal Boiling Point


  The boiling point at one atmospheric pressure
• Factors Affecting Boiling Point

  • Pressure (directly proportional)
  • Adding impurities (increases boiling point)
  • Structure (increases with number of carbon atoms, decreases with branching)
• Melting Point


  The temperature at which materials changes from a solid to a liquid
• Melting


  The point at which both liquid and solid phase exists at equilibrium
• Enthalpy of fusion/Entropy of fusion

  The energy supplied to melt a system
• Factors Affecting Melting Point


  • Molecular Symmetry (straight-chain higher than branched)
  • Molecular Size (longer carbon chains higher)
  • Polarity/Intermolecular Forces (polar higher than nonpolar)
  • Impurities (can lower melting point)