Mole Calculations

A mole is a fixed number (like a dozen or a grand). We don’t have to
know the number to do the calculations, just how many ‘moles’ there
are.

We can calculate the number of moles of a substance when given
the mass and the RFM (you can work it out!)
Mass
Moles
Ex.
X
RFM
Carbon is burned in oxygen to give carbon dioxide. What mass of
carbon dioxide can we make if we burn 24g of carbon in plenty
oxygen?
C
+
O2 
CO2
 Find the moles of carbon (use the triangle)
 Find the ratio of moles reacted (use the equation above)
 Find the mass of carbon dioxide (use the triangle)
Q1.
Calculate the mass of copper which would be formed if 320g of
copper (II) oxide was reacted with plenty of carbon according to
the equation,
2CuO +
Q2.
C
2Cu +
CO2
Calculate the mass of magnesium chloride produced in the reaction
of 12g of magnesium with plenty chlorine
Mg
+
Cl2

MgCl2
Q3.
Calculate the mass of sodium oxide produced in the reaction of 46g
of sodium with plenty of oxygen
4Na
Q.4
+
O2
2Na2O

a) Calculate the mass of hydrogen required to react with 56g of
nitrogen
N2
+
3H2

2NH3
b) Calculate the mass of ammonia (NH3) produced
Q5.
Calculate the mass of calcium sulphide produced when 80g of
calcium reacts with excess sulphur
Ca
Q6.
+
S

CaS
Calculate the mass of copper (II) oxide formed when 31g of copper
(II) carbonate is decomposed by heating
CuCO3

CuO
+
CO2
Q7.
Ammonia can be made by adding water to magnesium nitride.
Calculate the mass of ammonia produced when 30g of magnesium
nitride is added to excess water
Mg3N2
Q8.
+
6H2O
 3Mg(OH)2
+
2NH3
Nitrogen is used to fill the air bags which protect people in car
crashes. It is produced when sodium azide (NaN3) decomposes
rapidly
2NaN3

Na
+
N2
(a) The equation is not balanced. Balance the equation below
(b) A driver’s air bag contains 40g of sodium azide. What mass of
nitrogen can this produce?
(c) 28g of nitrogen has a volume of 24 litres. What volume of gas is
produced in the air bag?
*One mole of gas fills 24dm3
Q.9
The equation for the combustion of ethene (C2H4) is given below:
C2H4(g) + 3O2(g)  2CO2(g) + 2H2O(g)
(a) Calculate the volume of carbon dioxide produced when
200cm3 of ethene is burned
(b) Calculate the volume of oxygen required for this
Q10.
(a)
Write a balanced equation for nitrogen reacting with oxygen
to produce nitrogen dioxide (NO2). Remember your diatomics.
(b)
Calculate the volume of NO2 produced when 100cm3 of
nitrogen reacts with excess oxygen
(c)
Calculate the volume of nitrogen needed to fully react with
300cm3 of oxygen
Q11. In the Haber process, nitrogen and hydrogen react by the following
equation
N2 + 3H2  2NH3
(a)
What volume of ammonia (NH3) can be made from 10cm3
of nitrogen?
(b)
What volume of hydrogen would you need for this?
Q12. A gas mixture contains 100cm3 of methane and 100cm3 of hydrogen.
Calculate the minimum volume of oxygen required for the complete
combustion of this mixture (methane burns to give carbon dioxide
and water; you will have to write two equations)