Ch 5.

• Homogeneous mixture


  A mixture of substances composed of at least one solute and one solvent
• Solute


  Substance that is dissolved
• Solvent


  Substance that the solute is dissolved in
• Solutions


  • Homogeneous mixture
  • Clear (transparent) solutions
  • Can be coloured or colourless
  • Uniform mixture of entities (atoms, ions, and/or molecules)
• Heterogeneous mixture


  • Opaque or translucent (cloudy) mixture
• Why is milk a heterogeneous mixture?
• Possible combinations of solutes and solvents


  • Gas in gas
  • Gas in liquid
  • Gas in solid
  • Liquid in liquid
  • Solid in liquid
  • Solid in solid
• Possible combinations of solutes and solvents


  • Oxygen in nitrogen (air)
  • Oxygen in water
  • Oxygen in solid water (ice)
  • Methanol in water (antifreeze)
  • Sugar in water (syrup)
  • Tin in copper (Bronze alloy)
• Aqueous solutions


  Solute(s) dissolved in water = (aq) [state!]
• Solutes in aqueous solutions


  • Electrolytes: conduct electricity in aqueous solution (ionic compounds, acids and bases)
  • Non-electrolytes: aqueous solutions that do not conduct electricity (molecular compounds)
• Litmus testing


  Use litmus paper to determine if a compound is an acid, base, or neutral substance
• Litmus test results


  • Acids form acidic solutions, litmus turns red
  • Bases form basic solutions, litmus turns blue
  • Ionic and molecular compounds form neutral substances, litmus stays the same colour
• pH testing


  Solutions can be classified as: acidic (pH < 7, litmus turns red), basic (pH > 7, litmus turns blue), or neutral (pH = 7, litmus stays the same colour)
• Solution types


  • Ionic: conductive, acidic/basic
  • Molecular: non-conductive, neutral
  • Acid
  • Base
• Water is the most important solvent on Earth
• More ionic compounds are soluble in water than any other known solvent
• Dissociation


  The separation of ions that occurs when an ionic compound or a base dissolves in water
• If a compound is not soluble in water it will not dissociate
• Bases


  Ionic compounds (or ionic hydroxides) containing hydroxide that dissociate into a cation and a hydroxide anion [OH-]
• Acids


  Electrolytes, most acids are molecular compounds before being mixed with water, require ionization instead of dissociation
• Water ionizes acids. After ionization, acids are considered ionic compounds and are electrolytes
• Dissociation


  Separation of ions that already exist before dissolving in water, for ionic compounds and bases
• Ionization


  Production of new ions, specifically hydrogen ions in the case of acids
• Endothermic reactions absorb energy, exothermic reactions release energy
• In solution formation, breaking bonds in reactants is endothermic, making bonds in products is exothermic
• Exothermic reactions have more energy released by bond formation than consumed by bond breakage, endothermic reactions have less energy released by bond formation than consumed by bond breakage
• Entities present when a substance/compound is mixed with water


  • Ionic
  • Bases
  • Molecular
  • Acids (strong and weak)
  • Elements
• Solubility of ionic compounds can be determined using the solubility table
• If an ionic compound is soluble, list the ions and water
• If an ionic compound is only slightly soluble, list the solid and water
• Polar molecular compounds dissolve in water and become aqueous, non-polar molecular compounds do not dissolve and stay as a solid, liquid or gas
• Strong acids ionize (list ions and water), weak acids only partially ionize (list major entities and water)
• Elements have low solubility in water and stay the same when dropped in water
• Dissociation is the breaking up of a compound into ions, dissolving is when a compound changes state to (aq) after being put in water
• Percent concentration units: %m/m (g/g), %v/v (mL/mL), %m/v (g/mL)
• When calculating for concentration of solute, need to divide by 100, when calculating for concentration of solution, need to multiply by 100
• Concentration


  Expressed in moles per litre of solution, percent by mass, and parts per million
• Calculate concentration of solutions


  1. From empirical data, in moles per litre of solution

  2. Determine mass or volume from such concentrations
• Use data and ionization/dissociation equations


  Calculate the concentration of ions in a solution
• Dilute vs. concentrated


  Know the difference