Amount of substances

Created by

Jeremiah

Cards (14)

Relative atomic mass
Relative atomic mass of an element is the average mass of one atom of an element compared to 1/12 mass of one atom of 12C (carbon)
Relative molecular mass
The relative molecular mass is the average mass of one molecule of an element compared to 1/12 of 12C
Particles/molecules equation
Particles = moles × Avogadro's constant
Atom economy is another measure of the efficiency of a chemical reaction. This is the mass reactants that ends up as desired products.
Gas equation
$PV =$ $nRT$ P is for pressure measured in Pa units are Nm^-2 V is for volume measure in m^3 n is the number of moles R is the gas constant T is temperature measured in Kelvin
Percentage yield
Percentage yield = Actual yield / theoretical yield * 100% using moles
Atom economy
Mr of desired products / total Mr of all products * 100%
To increase atom economy you find a use or sell the waste products that's the only way.
You convert °C to Kelvin by adding 273
1 mole of gas is 24dm^3 volume
So volume of a gas is moles × 24
Reason to yield isn't 100%
Product loss through evaporation
Product loss through transference
Incomplete reaction
Reversible reaction
A side reaction
Reactants loss when adding
To calculate percentage error you do error of equipment/ volume measured *100
Calculating empirical formula
E.g. A compound contains 85.7g of carbon and 14.3g of hydrogen. What is it's empirical formula?
First work out moles
Moles = mass/Mr
Carbon moles = 85.7/12 =7.141
Hydrogen moles = 14.3/1 = 14.3
Divide moles by lowest mole
So 7.141/7.141 and 14.3/7.141
Would give a 1:2 ratio
Final answer would be CH2
Using mass spectrum to calculate molecular formula
First use the last value in that mass spectrum e.g. in the diagram that would be 42
Then do that value / Mr of empirical formula e.g. empirical formula = CH2 so 42/14 = 3
And use that answer to times it by the empirical formula to get molecular formula e.g. 3× CH2 = 3CH2