How to Sheet:
Calculate masses using equations:
Example question: 8g of Hydrogen is reacted with Oxygen how much water will it produce?
Method
1) Write out equation and balance e.g.
H2 + O2  H2O 
2H2 + O2  2H2O
2) Put in the masses given :
2H2 + O2  2H2O
Chemicals
Masses
RFM
Moles
Ratio
8g
H2
8g
1+1 = 2
?
?
H2O
?
?
?
?
3) Use the mass to work out the number of moles eg
Moles = Mass /RFM, so Moles of H2 = 8g/2 = 4moles of H2O put this in to the equation grid
Chemicals
Masses
RFM
Moles
Ratio
H2
8g
1+1 = 2
4 moles
H2O
?
4) Use equation to work out ratio, then use this to work out the number of moles of H2O.
As it is 1 to 1, if we have 4 moles of H2 then we get 4 moles of H2O
Chemicals
Masses
RFM
Moles
Ratio
H2
H2O
8g
?
1+1 =2
4 moles
4moles
2:2 so 1:1 (1 mole of H2 = 1 mole of H2O)
5) Finally use the mole equation to work out the mass of the H2O produced.
Moles = mass/RFM use the triangle to rearrange to get mass = moles x RFM
RFM of H2O = H+H+O = 1+1+16 = 18 so
Mass = moles x RFM = 4moles x18 = 72g
How to Sheet:
Calculate masses using equations:
Example question: 8g of Hydrogen is reacted with Oxygen how much water will it produce?
Method
1) Write out equation and balance e.g.
H2 + O2  H2O 
2H2 + O2  2H2O
2) Put in the masses given :
2H2 + O2  2H2O
Chemicals
Masses
RFM
Moles
Ratio
8g
H2
8g
1+1 = 2
?
?
H2O
?
?
?
?
3) Use the mass to work out the number of moles eg
Moles = Mass /RFM, so Moles of H2 = 8g/2 = 4moles of H2O put this in to the equation grid
Chemicals
Masses
RFM
Moles
Ratio
H2
8g
1+1 = 2
4 moles
H2O
?
4) Use equation to work out ratio, then use this to work out the number of moles of H2O.
As it is 1 to 1, if we have 4 moles of H2 then we get 4 moles of H2O
Chemicals
Masses
RFM
Moles
Ratio
H2
H2O
8g
?
1+1 =2
4 moles
4moles
2:2 so 1:1 (1 mole of H2 = 1 mole of H2O)
5) Finally use the mole equation to work out the mass of the H2O produced.
Moles = mass/RFM use the triangle to rearrange to get mass = moles x RFM
RFM of H2O = H+H+O = 1+1+16 = 18 so
Mass = moles x RFM = 4moles x18 = 72g