Chem - amount of sub

• Mole


  A way of measuring the amount of substance in chemistry, sometimes shortened to 'mol'
• Avogadro's number


  6.02 x 10^23, the number of atoms or molecules in one mole of any substance
• Calculating number of particles

  Avogadro's number x number of moles
• Mass and Mr/Ar


  The number of moles is the mass in grams divided by the Mr (molecular mass) or Ar (atomic mass)
• Calculating number of moles from mass

  Mass / Mr or Ar
• Solutions


  The number of moles in a substance in a solution can be calculated from its concentration and volume
• Calculating number of moles in a solution

  Concentration (mol/dm^3) x Volume (dm^3)
• Ideal gas equation


  PV = nRT, where P is pressure, V is volume, n is number of moles, R is the gas constant, and T is temperature in Kelvin
• Calculating volume of a gas

  V = nRT/P
• Unit conversions


  Multiply by powers of 10 to convert between meters, decimeters, and centimeters
• Converting units


  1. Multiply by 100 to go from meters to decimeters

  2. Multiply by 100 to go from decimeters to centimeters

  3. Multiply by 100 to go from meters to centimeters

  4. Multiply by 100 to go from square meters to square decimeters

  5. Multiply by 100 to go from square decimeters to square centimeters

  6. Multiply by 1000 to go from cubic meters to cubic decimeters

  7. Multiply by 1000 to go from cubic decimeters to cubic centimeters
• General rule for converting units

  For every dimension added, multiply by 100
• Ionic equation


  Shows the ions formed in solution and the particles reacting
• Ionic equations show the important ions involved in the reaction, with spectator ions cancelled out
• State symbols


  S = solid, L = liquid, G = gas, Aq = aqueous
• Calculating theoretical mass from a balanced equation

  1. Write balanced equation

  2. Calculate molar masses

  3. Divide mass of reactant by molar mass to find moles

  4. Use mole ratio to calculate moles of product

  5. Multiply moles of product by molar mass to get theoretical mass
• Calculating volume of gas from a balanced equation

  1. Write balanced equation

  2. Calculate moles of reactant

  3. Use mole ratio to calculate moles of gas product

  4. Use PV=nRT to calculate volume of gas
• Titration


  Used to determine the concentration of an acid or alkali by neutralization reaction
• Titration procedure


  • Add titrant to analyte until indicator changes colour (end point)
  • Read volume from burette meniscus at eye level
  • Repeat until two concordant results within 0.1 cm3
• Indicators


  • Phenolphthalein - colourless in acid, pink in alkali
  • Methyl orange - yellow in acid, red in alkali
• Calculating concentration from titration data

  1. Calculate moles of titrant from volume and concentration

  2. Use mole ratio from balanced equation to calculate moles of analyte

  3. Divide moles of analyte by volume to get concentration
• Reaction between HCl and potassium hydroxide

  1. Write balanced equation

  2. Calculate moles of HCl using concentration and volume

  3. Moles of potassium hydroxide is same as moles of HCl

  4. Calculate concentration of potassium hydroxide using moles and volume
• Calculating volume of sodium hydroxide being neutralized

  1. Write balanced equation

  2. Calculate moles of sulfuric acid using concentration and volume

  3. Use 1:2 ratio to calculate moles of sodium hydroxide

  4. Calculate volume of sodium hydroxide using moles and concentration
• Empirical formula


  Simplest whole number ratio of elements in a compound
• Determining empirical formula from composition data

  1. Write elements and their percentages

  2. Convert percentages to moles using relative atomic masses

  3. Divide moles by smallest to get whole number ratio
• Molecular formula


  Actual formula of a compound, can be different from empirical formula
• Percentage yield


  Actual yield divided by theoretical yield, times 100
• Atom economy


  Molecular mass of desired product divided by sum of molecular masses of all reactants, times 100
• Higher atom economy means more efficient use of raw materials, less waste, more sustainable