New
New
Year 10
Edexcel
Higher

Moles and masses

I can calculate mass of a substance or the number of moles it contains from data.

New
New
Year 10
Edexcel
Higher

Moles and masses

I can calculate mass of a substance or the number of moles it contains from data.

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Lesson details

Key learning points

  1. The number of particles (atoms, ions, molecules etc.) in one mole of a substance is always the same.
  2. The mass of one mole of a substance is equal to the relative mass of the substance measured in grams.
  3. Mathematical relationships are manipulated to process practical results, calculating the number of moles in a substance.

Common misconception

Pupils struggle to link a mole to number of particles.

Use real world examples of converting volumes / masses into number of particles so pupils become more comfortable converting between moles, number of particles particles and masses.

Keywords

  • Mole - A mole of something is 6.02 × 10²³ of it. The mass of a mole of a substance is its relative mass expressed in grams.

  • Avogadro's constant - Avogadro's constant is the number of particles in one mole of a substance (6.02 × 10²³ mol⁻¹).

  • Relative formula mass - The relative formula mass (RFM) of a substance is the sum of the relative atomic masses of all the atoms in a formula.

Equipment

Balances, pennys, small beakers, water, dropping pipettes, paper towels, calculators

Content guidance

  • Equipment requiring safe usage.

Supervision

Adult supervision recommended.

Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

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6 Questions

Q1.
Which of the following is the correct chemical formula for calcium carbonate?
CACO3
CaCo₃
CaCO
Correct answer: CaCO₃
CaC
Q2.
Match each keyword to the correct definition.
Correct Answer:chemical equation,describes a reaction, indicating the reactants and products

describes a reaction, indicating the reactants and products

Correct Answer:chemical formula,shows the number of atoms of each element in a substance

shows the number of atoms of each element in a substance

Correct Answer:coefficient,number placed in front of a chemical formula to balance an equation

number placed in front of a chemical formula to balance an equation

Correct Answer:subscript,written slightly below and to the side of another character

written slightly below and to the side of another character

Correct Answer:state symbol,indicates the physical state of substances in a reaction

indicates the physical state of substances in a reaction

Q3.
Which chemical equation is correctly balanced?
Mg + Cl → MgCl
Mg + Cl₂ → MgCl
Correct answer: Mg + Cl₂ → MgCl₂
Mg + 2Cl → MgCl₂
Q4.
Match each element to its correct relative atomic mass.
Correct Answer:He,4

4

Correct Answer:Be,9

9

Correct Answer:F,19

19

Correct Answer:Ne,20

20

Correct Answer:B,11

11

Correct Answer:Na,23

23

Q5.
The relative formula mass of sodium sulfide, Na₂S is .
Correct Answer: 78, 23 + 23 + 32, (23 × 2) + 32
Q6.
The relative formula mass of Al(OH)₃ is .
Correct Answer: 78, 27 + 16 + 16 + 16 + 1 + 1 + 1, 27 + (17 × 3), 27 + 3(16 + 1), 27 + 3×(16 + 1)

6 Questions

Q1.
Which equation best matches this description of a chemical reaction? "Four moles of aluminium atoms reacts with three moles of oxygen molecules to form two moles of aluminium oxide formula units".
2Al₂O₃ → 4Al + 3O₂
4Al → 2Al₂O₃ + 3O₂
3O₂ → 2Al₂O₃ + 4Al
Correct answer: 4Al + 3O₂ → 2Al₂O₃
Q2.
Which of the following shows a correct mathematical relationship between moles, mass (g), and a substance's relative formula mass (RFM)?
moles = mass (g) × relative formula mass
mass (g) = moles ÷ relative formula mass
Correct answer: mass (g) = moles × relative formula mass
Correct answer: moles = mass (g) ÷ relative formula mass
Q3.
The standard unit for mass is .
Correct Answer: grams, gram
Q4.
Place these samples in order from lowest mass to highest mass.
1 - 1 mol hydrogen
2 - 1 mol sodium
3 - 1 mol HCl
4 - 1 mol sodium chloride
5 - 1 mol Na₂O
6 - 1 mol Cl₂
Q5.
How does the number of particles in 10 g of nitric acid, HNO₃, compare to the number of particles in 10 g of nitrogen?
Correct answer: There are fewer nitric acid particles in 10 g
There are the same number of particles of nitrogen and nitric acid in 10 g
There are more nitric acid particles in 10 g
Q6.
Match the mass (g) to the correct number of particles (moles).
Correct Answer:6 g carbon ,0.5 mol

0.5 mol

Correct Answer:31 g phosphorus,1.0 mol

1.0 mol

Correct Answer:70 g MgS,1.25 mol

1.25 mol

Correct Answer:39 g LiF,1.5 mol

1.5 mol

Correct Answer:280 g Br₂,1.75 mol

1.75 mol

Correct Answer:80 g oxygen,2.5 mol

2.5 mol