amount of substance

• Mole


  The amount of substance in grams that has the same number of particles as there are atoms in 12 grams of carbon-12
• Relative atomic mass


  The average mass of one atom compared to one twelfth of the mass of one atom of carbon-12
• Molar mass


  The mass in grams of 1 mole of a substance and is given the unit of g mol-1
• Molar gas volume


  The volume of 1 mole of a gas at a given temperature and pressure. At room pressure (1atm) and room temperature 25oC the molar gas volume is 24 dm3 mol–1
• For pure solids, liquids and gases, the unit of mass is grams and the unit of amount is mol
• Avogadro's constant


  There are 6.02 x 1023 atoms in 12 grams of carbon-12. Therefore, one mole of any specified entity contains 6.02 x 1023 of that entity
• Significant Figures


  Give your answers to the same number of significant figures as the number of significant figures for the data you given in a question
• Empirical formula


  The simplest ratio of atoms of each element in the compound
• Molecular formula


  The actual number of atoms of each element in the compound
• Heating in a crucible

  1. Weigh an empty clean dry crucible and lid

  2. Add 2g of hydrated calcium sulfate to the crucible and weigh again

  3. Heat strongly with a Bunsen for a couple of minutes

  4. Allow to cool

  5. Weigh the crucible and contents again

  6. Heat crucible again and reweigh until you reach a constant mass
• Hydrated salt


  A salt that contains water of crystallisation
• Concentration of solutions


  • Concentration = amount/volume
  • Unit of concentration: mol dm-3 or M
  • Unit of Volume: dm3
• Converting volumes


  • cm3 to dm3: divide by 1000
  • cm3 to m3: divide by 1000 000
  • dm3 to m3: divide by 1000
• Mass Concentration


  • Concentration measured in g dm-3
  • conc in g dm-3 = conc in mol dm-3 x Mr
• Ions dissociating


  When soluble ionic solids dissolve in water they will dissociate into separate ions
• Flammable - keep away from open flames
• Oxidising - keep away from flammable/easily oxidised materials
• Ideal gas equation

  PV = nRT, P = pressure in Pa, V = Volume in m3, n = moles, T = Temperature in K, R = 8.314
• Temperature conversion

  °C in K: +273
• Molar Gas volume at rtp

  v = n x 24dm3/24000cm3
• We can do this as the moles of gas do not change
• Equation for relating pressure, volume and temperature

  1. P1V1/T1 = P2V2/T2

  2. If Temperature is the same can make the above equation P1V1 = P2V2
• P2 = (P1V1)/V2
• P2 = (100000 x 1x 10-4) / (5x10-4) = 20 000Pa
• Calculating volume of 50.0 g of carbon dioxide gas at room temperature and pressure

  1. amount = mass/Mr

  2. Gas volume (dm3) = amount x 24
• Molar Gas Volume


  The volume occupied by one mole of any gas at standard temperature and pressure (STP)
• Avogadro's Constant


  There are 6.02 x 10^23 atoms/molecules/ions in one mole of any substance
• Avogadro's constant can be used for atoms, molecules and ions
• Calculating number of atoms in a sample

  1. amount = mass/Ar

  2. Number atoms = amount x 6.02 x 10^23
• Calculating number of ions in a solution

  1. amount = concentration x Volume

  2. Number ions = amount x 6.02 x 10^23
• Density


  Mass per unit volume, usually given in g cm-3
• Calculating number of molecules in a liquid volume

  1. Mass = density x volume

  2. amount = mass/Mr

  3. Number of molecules = amount x 6.022 x 10^23
• Calculating density from mass and volume

  density = mass/volume
• Balanced equation


  Mole ratios between reactants and products
• Converting quantities between substances using a balanced equation

  1. Step 1: Convert given quantity to amount in mol

  2. Step 2: Use balanced equation to convert amount of one substance to amount of another

  3. Step 3: Convert amount in mol to desired quantity
• Limiting reactant


  The reactant that is completely used up, limiting the amount of product formed
• Percentage yield


  Actual yield / Theoretical yield x 100
• Percentage atom economy


  Mass of useful products / Mass of all reactants x 100