mole
the unit for the amount of substance. This is the amount of chemical species found in 12 g of C12
avogadro’s constant
the number of atoms in exactly 12 g of 12C (6.02 x 10^23/mol)
molar mass
mass of one mole of the substance expressed in g/mol.
empirical formula
smallest whole number ratio of atoms of each element in a compound
molecular formula
the actual number of atoms of each element in a compound
spectator ions
ions that do not take part in the reaction
hydrate
a compound that has molecules of water of crystallisation, e.g. MgSO . 7 H2O
solution
solute (is dissolved) + solvent (dissolves the solute). Standard solution is the one with accurately known concentration
mass concentration
mass of solute per volume of solution, g/dm^3
molar concentration
moles of solute per volume of solution, mol/dm^3
primary standard
a substance used for preparation of a standard solution by weighing
avogadro’s law
provided the conditions of temperature and pressure are the same, equal volume of gases contain the same number of molecules
molar volume
the volume of 1 mol of a gas
displacement reaction
more reactive element reacts to take place of less reactive element in a compound
precipitation reaction
reaction that produces an insoluble solid
error
a discrepancy between the value obtained in the experiment and an actual value
precision
refers to how close to each other are the values obtained in an experiment
accuracy
refers to how close these values are to the actual value
concordant results
results that lie close to each other. In titration, these are titres that usually lie within +/-0.20 cm^3
margin of error
the range in which the true value of a measurement could lie, e.g. for burettes +/-0.05 cm^3
random errors
they occur when conditions are varied in an unpredictable manner.
systematic errors
errors which are constant when you repeat an experiment. They usually are a result of the apparatus used.
atom economy
measure of the proportion of reaction atoms that become part of the desired product in the balanced chemical equation/. atom economy = (molar mass of desired product/ total molar mass of products) x 100
percentage uncertainty
(uncertainty/reading) x 100
