1. On the back, write down everything this tells you

2. Calculate the mass of 1 mole of the following atoms:
Mg, Li, Cl, Au
Calculate the Concentration
50g of sodium chloride in 2.5dm3 of water.
1.8g of sodium carbonate in 862 cm3 of water.
A student had a solution of sodium chloride with a concentration of 93.6g/dm3. Calculate the mass of sodium chloride dissolved in 25cm3 of the solution.
What is the definition of concentration and what are the units?
How do you convert cm3 into dm3?
How do you convert m3 into dm3?

3. Calculate the mass of 1 mole of the following atoms:
Mg, Li, Cl, Au

4. The mass of a mole of an atom
Easy – it’s just the relative atomic mass in grams.
For example, carbon has a relative atomic mass of 12, so the mass of a mole would be 12g.

5. Moles Mg Li Cl Au Calculate the mass of 1 mole of the following atoms:24 7
35.5
16 (there would be the same number of atoms0

6. Relative Formula Mass
You can use the relative atomic mass of different elements to work out the relative formula mass of compounds.
For example, NaCl:
Na = 23
Cl = 35.5
So NaCl = 58.5

7. Relative Formula Mass LiF H2O H2SO4 C6H12O6 Ca(OH)2
Calculate the relative formula mass for these examples:
LiF
H2O
H2SO4
C6H12O6
Ca(OH)2
LiF = 26
H2O = (1x2) + 16 = 18
H2SO4 = (1x2) (16 x 4) = 98
C6H12O6 = = 180
Ca(OH)2 = 74

8. Boardworks GCSE Additional Science: Formulae and Equations
Percentage by Mass
The percentage by mass of an element in a compound is sometimes known as the percentage composition.
Percentage by mass is calculated using the relative atomic mass and relative atomic mass
× 100
% element =
RAM of element × number of atoms
r.f.m of compound

9. Calculating percentage by mass – example 1
Boardworks GCSE Additional Science:
Formulae and Equations
What percentage by mass of nitrogen is in ammonia (NH3)? (RAM: H = 1, N = 14)
Step 1: Work out the relative formula mass (RFM) of NH3.
RFM of NH3
= 1 nitrogen atom + 3 hydrogen atoms
= (1 × 14) + (3 × 1)
= 17
Step 2: Work out the percentage by mass of nitrogen.
RAM × number of atoms
RFM of compound
× 100 =
% of nitrogen in NH3 17
× 100 =
(14 × 1)
= 82%

10. Calculating percentage by mass – example 2
Boardworks GCSE Additional Science:
Formulae and Equations
What percentage by mass of hydrogen is in ammonia (NH3)? (RAM: H = 1, N = 14)
Step 1: Work out the relative formula mass (RFM) of NH3.
RFM of NH3
= 1 nitrogen atom + 3 hydrogen atoms
= (1 × 14) + (3 × 1)
= 17
Step 2: Work out the percentage by mass of hydrogen.
RAM × number of atoms
RFM of compound
× 100 =
% of hydrogen in NH3 17
× 100 =
(1 x 3)
= 18%

11. Percentage by Mass What is the percentage by mass of oxygen in: MgO
K2O
NaOH
SO2
MgO = 40%
K2O = 17%
NaOH = 40%
SO2 = 50%

12. Percentage Yield
The percentage yield tells us about the amount of product that a chemical reaction produces.
Very few chemical reactions have a yield of 100%.
percentage yield = ×
actual yield
theoretical yield
100

13. Calculating Percentage Yield
I reacted copper sulphate solution with some iron. I worked out that the theoretical yield of the reaction was 50g of copper.
I lost some copper when I filtered the solution and ended up with 40g.
What is the percentage yield of the reaction?
40 g
50 g
percentage yield = × 100 = 80%

14. Calculating Percentage Yield
A chemical factory was planning to make 500 tonnes of calcium oxide by heating calcium carbonate. They produced 450 tonnes. What was the percentage yield?
A drug company carried out a test reaction, aiming to make 1g of a new cancer drug. The reaction only produced 0.7g of the drug. What was the percentage yield?
Walter White tried out a new method to make 20 kg of crystal meth. However, he only produced 17.5 kg. What was his percentage yield?
90%
70%
87.5%

15. Question Race
Who will win?

16. To finish In the back of your book:
What are you better at now compared to the start of the lesson?