AQA A LEVEL CHEMISTRY
✔✔Molecular Formula - ✔✔The actual number of atoms of each element in a
compound
✔✔Empirical Formula to Molecular Formula - ✔✔1 ) Find the Mr of the empirical formula
2 ) Divide the given Mr of the molecular formula by the Mr of the empirical formula
3 ) Multiply the number of each atoms in the empirical formula by this value
✔✔Molecular Formula to Empirical Formula - ✔✔Find the simplest whole number ratio
by dividing the number of each value by the lowest number in the compound
✔✔Determining the Formulae of Simple Compounds Using Percentages - ✔✔-Assume
that there is 100g of the compound being asked about, therefore calculate the moles of
each part of the compound and work out the ratio of these molar values by dividing
them each by the smallest amount of moles (the ratio value for one part of the
compound will therefore be 1) and use this to work out the formula
✔✔Determining the Formula of Simple Compounds Using Masses - ✔✔Calculate the
amount in moles of each part of the compound and then use this to find the ratio by
dividing each molar value by the lowest value calculated and then use these values to
deduce the formula of the compound
✔✔Determining the Degree of Hydration - ✔✔1 ) Use the mass of the anhydrous to
compound to find the mass of the water
2 ) Use the Mr's of the anhydrous compound and the water to calculate the moles of
each aspect and the use these to find the ratio between them which will give you the
value of x or n
✔✔Calculating Atom Economy - ✔✔Divide the molecular mass of the desired product
(its Mr) by the sum of the of the molecular masses of the reactants (their combined Mr's)
the multiply by 100
✔✔Understanding Percentage Yield - ✔✔The higher the percentage yield, the more
efficient the reaction is
✔✔Understanding Atom Economy - ✔✔The lower the atom economy, the more waste
the reaction produces
✔✔Finding the Limiting Reagent - ✔✔1 ) If necessary, calculate the mass of one of the
reactants being asked about
2 ) Convert the masses into moles
3 ) Calculate the actual ratio by dividing the molar values by the lowest molar values
calculated (the ratio value should therefore be 1 for one of the reactants)
, 4 ) Compare this to the ratio given by the balanced equation and use this to deduce the
limiting reagent
✔✔ Relative Atomic Mass - ✔✔The average mass of an atom of an element, compared
to that of the mass of 1/12th of the average mass of an atom of carbon-12
✔✔Relative Molecular Mass - ✔✔The average mass of one molecule compared to
1/12th of the mass of one atom of carbon-12
✔✔Avogadro Constant - ✔✔The number of particles in one mole of an atom: 6.022 x
10^23
✔✔Solvent - ✔✔A liquid that can have a substance dissolved into it
✔✔Solute - ✔✔A solid that can be dissolved
✔✔Solution - ✔✔A solute dissolved in a solvent
✔✔Ideal Gas Equation - ✔✔pV = nRT
✔✔Concentration - ✔✔Moles / Volume
Amount of substance in moles dissolved in 1dm3 of solution
Mol dm-3
✔✔Moles (mass) - ✔✔Mass / Mr
✔✔Atom Economy - ✔✔Mr of producta/ sum of Mr of all reactants x 100
✔✔Percentage Yield - ✔✔(actual output / predicted output) x 100
✔✔Calculating empirical formula - ✔✔1. % by mass
2. Divided by Ar
3. Divide by smallest
✔✔Calculate molecular formula - ✔✔Relative molecular mass divided by relative mass
of empirical formula
✔✔equation for amount of moles (Avogadro constant) - ✔✔amount of moles = number
of particles / Avogadro constant
✔✔4 reasons for lack of 100% percentage yield? - ✔✔loss by mechanical transfer, loss
during separating technique, unwanted side reactions, reaction not complete
✔✔units - ✔✔1cm3 - 1ml
✔✔Molecular Formula - ✔✔The actual number of atoms of each element in a
compound
✔✔Empirical Formula to Molecular Formula - ✔✔1 ) Find the Mr of the empirical formula
2 ) Divide the given Mr of the molecular formula by the Mr of the empirical formula
3 ) Multiply the number of each atoms in the empirical formula by this value
✔✔Molecular Formula to Empirical Formula - ✔✔Find the simplest whole number ratio
by dividing the number of each value by the lowest number in the compound
✔✔Determining the Formulae of Simple Compounds Using Percentages - ✔✔-Assume
that there is 100g of the compound being asked about, therefore calculate the moles of
each part of the compound and work out the ratio of these molar values by dividing
them each by the smallest amount of moles (the ratio value for one part of the
compound will therefore be 1) and use this to work out the formula
✔✔Determining the Formula of Simple Compounds Using Masses - ✔✔Calculate the
amount in moles of each part of the compound and then use this to find the ratio by
dividing each molar value by the lowest value calculated and then use these values to
deduce the formula of the compound
✔✔Determining the Degree of Hydration - ✔✔1 ) Use the mass of the anhydrous to
compound to find the mass of the water
2 ) Use the Mr's of the anhydrous compound and the water to calculate the moles of
each aspect and the use these to find the ratio between them which will give you the
value of x or n
✔✔Calculating Atom Economy - ✔✔Divide the molecular mass of the desired product
(its Mr) by the sum of the of the molecular masses of the reactants (their combined Mr's)
the multiply by 100
✔✔Understanding Percentage Yield - ✔✔The higher the percentage yield, the more
efficient the reaction is
✔✔Understanding Atom Economy - ✔✔The lower the atom economy, the more waste
the reaction produces
✔✔Finding the Limiting Reagent - ✔✔1 ) If necessary, calculate the mass of one of the
reactants being asked about
2 ) Convert the masses into moles
3 ) Calculate the actual ratio by dividing the molar values by the lowest molar values
calculated (the ratio value should therefore be 1 for one of the reactants)
, 4 ) Compare this to the ratio given by the balanced equation and use this to deduce the
limiting reagent
✔✔ Relative Atomic Mass - ✔✔The average mass of an atom of an element, compared
to that of the mass of 1/12th of the average mass of an atom of carbon-12
✔✔Relative Molecular Mass - ✔✔The average mass of one molecule compared to
1/12th of the mass of one atom of carbon-12
✔✔Avogadro Constant - ✔✔The number of particles in one mole of an atom: 6.022 x
10^23
✔✔Solvent - ✔✔A liquid that can have a substance dissolved into it
✔✔Solute - ✔✔A solid that can be dissolved
✔✔Solution - ✔✔A solute dissolved in a solvent
✔✔Ideal Gas Equation - ✔✔pV = nRT
✔✔Concentration - ✔✔Moles / Volume
Amount of substance in moles dissolved in 1dm3 of solution
Mol dm-3
✔✔Moles (mass) - ✔✔Mass / Mr
✔✔Atom Economy - ✔✔Mr of producta/ sum of Mr of all reactants x 100
✔✔Percentage Yield - ✔✔(actual output / predicted output) x 100
✔✔Calculating empirical formula - ✔✔1. % by mass
2. Divided by Ar
3. Divide by smallest
✔✔Calculate molecular formula - ✔✔Relative molecular mass divided by relative mass
of empirical formula
✔✔equation for amount of moles (Avogadro constant) - ✔✔amount of moles = number
of particles / Avogadro constant
✔✔4 reasons for lack of 100% percentage yield? - ✔✔loss by mechanical transfer, loss
during separating technique, unwanted side reactions, reaction not complete
✔✔units - ✔✔1cm3 - 1ml
