BRAINCAKEQuantitative chemistry
Revision notes for Quantitative chemistry in AQA Chemistry (8462). Every lesson in BrainCake comes with R.E.C.I.P.E. recall steps, a quick check and spaced reviews.
- Conservation of mass and balanced chemical equationsThe law of conservation of mass says that no atoms are lost or made during a chemical reaction.
- Relative formula massThe relative formula mass (Mr) of a compound is the sum of the relative atomic masses (Ar) of all the atoms in the numbers shown in the formula.
- Mass changes when a reactant or product is a gasSome reactions appear to gain or lose mass, but no atoms are lost or made.
- Chemical measurementsWhenever a measurement is made there is always some uncertainty about the result.
- Moles (HT only)Chemical amounts are measured in a unit called the mole, which has the symbol mol.
- Amounts of substances in equations (HT only)A balanced symbol equation can be read in terms of moles.
- Using moles to balance equations (HT only)The balancing numbers in an equation can be worked out from the masses of the reactants and products.
- Limiting reactants (HT only)In many reactions one reactant is used in excess.
- Concentration of solutionsMany reactions happen in solutions.
- Percentage yieldIn a chemical reaction no atoms are gained or lost, but you rarely collect all the product the equation predicts.
- Atom economyThe atom economy (also called atom utilisation) is a measure of how much of the starting materials end up as useful products.