Quantitative Chemistry

• law of conservation of mass

  no atoms are lost or made during a chemical reaction so the mass of the products equals the mass of the reactants
• define relative atomic mass and relative formula mass


  • RAM - average mass of atoms in an element taking into account masses and abundance of its isotopes
  • RFM - sum of all RAM’s of all atoms in the formula
• what is Avogadro’s constant?

  • number of atoms, molecules or ions in a mole of a given substance
  • 6.02x10^23
• formula linking mass, molecular mass and moles together

  mass = Mr x moles
• what is meant by a limiting reactant in a chemical reaction?

  • in a chemical reaction involving two reactants, common to use an excess of one of the reactants to ensure that all of the other reactant is used
  • reactant that is completely used up is called the limiting reactant because it limits the amount of products
• two formulae that links concentration, mass and volume together

  • concentration (g per dm3) = mass(g) / volume(dm3)
  • concentration (mol per dm3) = number of moles / volume (dm3)
• what is the molar volume of a gas at room temperature and pressure?

  1 mole of a gas at room temperature and pressure occupies 24dm3
• what is titration?

  technique for finding the concentration of a solution by reacting a known volume of this solution with a solution of known concentration
• why is it not always possible to obtain the theoretical amount of product in a chemical reaction?

  • reaction may not go to completion because it’s reversible
  • some of the product may be lost when it is separated from the reaction mixture
  • some of the reactants may react in ways different to the expected reaction (side reactions may occur)
• percentage yield equation

  percentage yield = (actual yield / theoretical yield) x100
• what is atom economy?

  • measure of the atom of starting materials that ends up as useful products
  • ratio of the relative formula mass of desired product to the sum of relative formula masses of reactants
• atom economy equation

  total Mr of desired product / total Mr of all reactants