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• Conservation of mass


  No atoms are lost or made during a chemical reaction
• Balanced chemical equation


  Mass of products = mass of reactants
• Relative formula mass (Mr)


  Sum of the relative atomic masses of the atoms in the numbers shown in the formula
• Calculating % by mass

  Mass of element/mass of RFM x 100
• Reactant or product is a gas


  Mass changes observed in non-enclosed systems during a chemical reaction
• Uncertainty


  Represents the distribution of results and makes estimations of uncertainty
• Uncertainty


  Range about the mean as a measure of uncertainty
• Mole


  Chemical amounts are measured in moles (mol)
• Mole


  Mass of one mole of a substance in grams is numerically equal to its relative formula mass
• Mole


  One mole of a substance contains the same number of the stated particles, atoms, molecules or ions as one mole of any other substance
• Avogadro constant


  6.02 x 10^23 per mole
• Calculating number of moles

  Mass (g)/ RFM
• Balancing chemical equations


  Converting the numbers of moles to ratios
• Limiting reactant


  Reactant that is completely used up, limits the amount of products
• Concentration of solution


  Mass/volume (g/dm3) or mol/dm3
• Calculating mass of solute in a given volume of solution

  Given concentration in terms of mass per given volume of solution
• Percentage yield


  Amount of product obtained compared to maximum theoretical amount
• Atom economy


  Amount of starting materials that end up as useful products
• Calculating volume of gases

  Equal amounts in moles of gases occupy the same volume under the same conditions of temperature and pressure
• Volume of one mole of any gas at room temperature and pressure = 24 dm^3