2.1.3 Amount Of Substances Flashcards
How many particles are in a mole?
6.02 x 10 23
What is the mass of one mole of carbon?
12g
How many atoms in 12g of carbon?
6.02 x 10 23 atoms
What is molar mass Mr measured in
gmol-1 or g/mol
Moles (mol) =
Mass (g)
————
RFM/Mr (g mol-1)
How to work out empirical formula with a given mass or percentage composition by mass
Find the moles by mass / RFM and divide the other moles by the smallest moles to find ratio
How many centimetres/millilitres/litres in 1 dm3?
1000cm3 or 1000ml or 1L
Concentration (mol dm-3) =
Moles(mol)
——————
Volume(dm3)
How to calculate volume (cm3) from moles and concentration
Vol = mol/mol dm-3 = dm3 x 1000 = cm3
How to calculate mass from concentration and volume
Find the moles and fill into moles = mass/rfm
What is the volume of one mole of a gas molecule at room temperature and pressure
24dm3 / 24000cm3
Percentage yield =
Actual yield/ theoretical yield
Atom economy =
Sum of Mr of desired products/ sum of Mr of all products
pV =
pa x m3
nRT
Mol x x k
K =
C + 273
How to convert from cm3 to m3 and dm3 to m3
Divide by 1 million
Divide by 1000
Gas volume =
Moles x 24dm3 or 24000cm3
Concentration of mass gdm-3 =
Concentration mol dm-3 x RFM g mol-1
Why isn’t percentage yield 100%?
- Lost due to mechanical transfer
- Loss whilst separating e.g. filtration funnel
- Side reactions(reactants or products react with something unexpected)
- incomplete reactions
Why are products with higher atom economies better?
They produce a larger proportion of desired products and less unwanted waste products and are important for sustainability as they make the best use of natural resources
When calculating atom economy, do we include number of moles in the calculation?
Yes
How many grams in a ton?
1000000
What is weighted mean mass
Average mass of an atom or molecule taking into account the abundance of isotopes
What does (.xH2O) represent
Water of crystallisation
why is C12 used to compare atomic masses
It is the agreed standard
Explain clearly the difference between atom economy and percentage yield
% yield compares the amount produced compared to the amount you should get, atom economy is the proportion
of the mass of all the products that is the desired product
How to find the number of atoms in a molecule
Find the number of moles and X by 6.02× 10 23
What is the apparatus used to measure gas volume produced?
A gas syringe or a conical flask and measuring cylinder
How to calculate atom economy
RFM of design products divided by sum of RFM of all products X100
What is the equation for complete combustion?
Fuel + O2 = CO2 + H2O
