Quantitative chemistry

• The total mass of all substances is conserved in a chemical reaction
• The number of atoms, molecules or ions in a mole of a given substance is the Avogadro constant. The value of the Avogadro constant is 6.02 x 10^23 per mole.
• moles = mass/Mr or rearranged to mass = Mr x moles
• No of particles = number of moles X Avogadro's constant
• In a chemical reaction involving two reactants, it is common to use an excess of one of the reactants to ensure that all of the other reactant is used. The reactant that is completely used up is called the limiting reactant because it limits the amount of products.
• Concentration(in mol/dm3 ) = moles/volume (in dm3 ) Concentration(in g/dm3 ) = mass (in g) /volume (in dm3 )
• To convert cm3 into dm3 divide by 1000 and to convert a concentration in g/dm3 to mol/dm3 divide by Mr
• % Yield = (Mass of product actually made / maximum theoretical mass of product) x 100
• Theoretical yield = Mass of limiting reactant x % theoretical yield
• Percentage atom economy = (mass of desired product / mass of desired product + mass of all other products) x 100
• The volume of one mole of any gas at room temperature and pressure (20oC and 1 atmosphere pressure) is 24 dm3. Gas Volume (dm3 )= number of moles x 24