Chemistry: Quantitative Chemistry: Key terms

• Conservation of mass


  the total mass of the products of a chemical reaction is always equal to the total mass of the reactants
• Half equation


  used to show what happens to one of the reactants in a chemical reaction
• Ionic equation

  a simplified version of a chemical equation, which just shows the species that are involved in the reaction
• Species


  the different atoms, molecules or ions that are involved in a reaction
• Relative formula mass (Mr)


  the sum of the relative atomic masses of all the atoms shown in the formula
• Relative atomic mass (Ar)

  the ratio of the average mass per atom of the element to one-twelfth the mass of an atom of carbon-12
• Mole (mol)


  the unit for measuring the amount of substance; one mole of any substance contains the same number of particles; the mass of one mole of a substance is equal to the relative formula mass in grams
• Avogadro constant


  the number of particles in one mole of any substance, i.e. six hundred thousand billion billion or 6.02 ×1023
• Limiting reactant

  the reactant that is completely used up in a reaction; it stops the reaction from going any further and any further products being produced
• Concentration


  the amount of substance in a given volume, normally measured in units of mol/dm3
• Solute


  a substance that dissolves in a solvent to form a mixture called a solution
• Titration

  an accurate technique that can be used to find out how much of an acid is needed to neutralise an alkali
• Indicator


  a chemical that is one colour in an acid and another colour in an alkali
• Percentage yield


  a calculation used to compare the actual yield of a product obtained from a reaction with the maximum theoretical yield
• Atom economy


  a measure of the amount of reactant converted to a useful product, i.e. relative formula mass of the desired product / sum of the relative formula mass of all the products/reactants; it can be stated as a number or a percentage
• Sustainable development


  development that meets the needs of the current generation without compromising the ability of future generations to meet their own needs
• Hydration

  a reaction in which H2 O is added to a substance
• Fermentation


  a chemical reaction in which alcohol and carbon dioxide are produced from glucose
• Addition reaction


  a reaction in which the reactants join together to form one product