1. - gives numbers of moles reacting
C Equations
and calculations
H O H2O 2 2
2 moles H2
2 x (1x2)
= 4 g
1 mole O2
(16 x2)
= 32 g
2 mole H2O
2x ( )
= 36 g
Q. How many grams of Hydrogen
and oxygen are needed to
make 72g water ? H =1 O = 16
1. Balance the equation
- gives numbers of moles reacting
2. Calculate masses reacting
- from the RAMs
3. Divide by molar quantity and x by 72g

2. 3. Divide by molar quantity and x by 72g
C Equations
and calculations
H O H2O 2 2
2 moles H2
2 x (1x2)
= 4 g
1 mole O2
(16 x2)
= 32 g
2 mole H2O
2x ( )
= 36 g
4 x 72g = 8 g 36
Hydrogen
32 x 72g = 64 g 36
Oxygen
36 x 72g = 72g 36
Water
3. Divide by molar quantity and x by 72g

3. C2 3.4 Equations Ca CO3 CaO + CO2 heat and calculations limestone lime
1 mole CaCO3
(16x3)
= 100 g
1 mole CaO
= 56 g
1 mole CO2
12 + (16x2)
= 44 g
Q. How many tonnes of lime could be obtained
from 250 tonnes of limestone?
H =1 O = 16 Ca 40 C= tonne = 1,000,000g
1. Balance the equation
- gives numbers of moles reacting
2. Calculate masses reacting
- from the RAMs
3. Divide by molar quantity
and x by 250 tonnes

4. C2 3.4 Equations and calculations Ca CO3 CaO + CO2 limestone lime heat
1 mole CO2
12 + (16x2)
= 44 g
1 mole CaO
= 56 g
1 mole CaCO3
(16x3)
= 100 g
44 x 250 = 110
100
tonnes of CO2
100 x 250 = 250
100
tonnes of Limestone
56 x 250 = 140
100
tonnes of lime
Q. How many tonnes of lime could be obtained
from 250 tonnes of limestone?
H =1 O = 16 Ca 40 C= tonne = 1,000,000g
3. Divide by molar quantity
and x by 250 tonnes

5. e b mo ma p
H2O H2O O2 2 2
Calculate masses reacting from the RAMs
Then divide each term by 80 then multiply each term by 60
2x 40g (16x2)g gives (40 +16)g
So 60g calcium reacts with 24 g oxygen