New
New
Year 10
AQA
Higher

Determining an equation experimentally: magnesium oxide

I can describe a safe experiment to calculate the reacting molar ratios for the oxidation of magnesium.

New
New
Year 10
AQA
Higher

Determining an equation experimentally: magnesium oxide

I can describe a safe experiment to calculate the reacting molar ratios for the oxidation of magnesium.

Lesson details

Key learning points

  1. Heating magnesium in a crucible will react it with oxygen.
  2. The crucible must be opened periodically to ensure enough oxygen enters the vessel to completely oxidise the magnesium.
  3. Opening the crucible too much will cause mass/product loss.
  4. Safety precautions should be taken when burning magnesium because of the bright light produced.
  5. The stoichiometry for a reaction can be calculated given experimental data.

Common misconception

Pupils sometimes struggle to understand that 'heating to constant mass' takes time and multiple measurements.

Link the idea that atoms rearrange during a reaction and that for all atoms of a substance to be oxidised, enough oxygen must be present. If the product measurements show a 'constant mass' we can be confident that complete oxidation has occurred.

Keywords

  • Limiting reactant - the reactant that completely reacts, thereby determining the maximum amount of product that can be formed in a chemical reaction. All other reactants will be present in excess

  • Ratio - used to determine the size of one quantity in relation to another

  • Stoichiometry - the molar ratio of the reactants and products in a chemical reaction

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

  • Balanced symbol equation - describes a reaction using a symbol equation with coefficients which ensure there are equal numbers of atoms of each element on both sides of the equation

This lesson presents a fantastic opportunity to bring together multiple aspects of the topic; types of reactions, conservation of mass, moles, limiting reactants, practical skills, equipment choice, etc. Opportunities to adapt it to the needs of the class/provide extension activities is extensive!
Teacher tip

Equipment

Mg strip, crucible + lid, clay triangle, tripod, Bunsen burner, heatproof mat, tongs, balance.

Content guidance

  • Risk assessment required - equipment

Supervision

Adult supervision required

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.
Match the following terms to the correct definition.
Correct Answer:Oxidation,Reaction in which oxygen atoms bond to the elements of the reactants.

Reaction in which oxygen atoms bond to the elements of the reactants.

Correct Answer:Limiting reactant,The reactant that completely reacts during a reaction.

The reactant that completely reacts during a reaction.

Correct Answer:In excess,A reactant that remains at the end of a reaction.

A reactant that remains at the end of a reaction.

Correct Answer:Molar ratio,How many moles of each chemical we need to react to make the products.

How many moles of each chemical we need to react to make the products.

Q2.
True of false? Combustion is an example of an oxidation reaction.
Correct answer: True
False
Q3.
Which of the following equations describes an oxidation reaction?
iron + sulfur → iron sulfide
Correct answer: sulfur + oxygen → sulfur dioxide
copper carbonate → carbon dioxide + copper oxide
sodium + bromine → sodium bromide
Q4.
The formula for glucose is C₆H₁₂O₆. Which of the following statements about glucose are correct?
The ratio of carbon to hydrogen is 2 : 1
Correct answer: The ratio of oxygen to hydrogen is 1 : 2
Correct answer: The ratio of carbon to oxygen is 1 : 1
The ratio of hydrogen to carbon is 1 : 2
Q5.
Which of the following are examples of oxidation reactions?
Correct answer: CH₄ + 2O₂ → CO₂ + 2H₂O
CuO + H₂ → Cu + H₂O
6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
N₂ + 3H₂ → 2NH₃
Q6.
What is the ratio of oxygen to carbon dioxide in the following equation? CH₄ + 2O₂ → CO₂ + 2H₂O
Correct answer: 2 : 1
1 : 1
1 : 2
2 : 2

6 Questions

Q1.
Match the following terms to the correct definition.
Correct Answer:Stoichiometry,The molar ratio of the reactants and products in a chemical reaction.

The molar ratio of the reactants and products in a chemical reaction.

Correct Answer:Mole,The unit of substance.

The unit of substance.

Correct Answer:Limiting reactant,Substance that completely reacts during a reaction.

Substance that completely reacts during a reaction.

Correct Answer:Constant mass,The mass remains the same.

The mass remains the same.

Q2.
Which of the following is an example of a closed environment?
Heating magnesium in a Bunsen burner flame.
Heating magnesium in a beaker.
Correct answer: Heating magnesium in a crucible with a lid.
Heating magnesium in an evaporating basin.
Q3.
Which of the following are advantages of using a crucible and lid to heat magnesium?
Correct answer: Potentially loses less product.
Is fast.
Is easy to observe.
Correct answer: Protects scientists from the bright light produced.
Q4.
Use the following information to calculate the mass of oxygen that reacted with the magnesium to form magnesium oxide. Mass of magnesium = 4.78 g; mass of magnesium oxide = 7.56 g. 2Mg + O₂ → 2MgO
0.00 g
Correct answer: 2.78 g
4.78 g
9.56 g
Q5.
When magnesium is heated in a crucible the lid is occasionally opened. This makes sure the oxygen ...
Correct answer: is in excess.
is limiting.
escapes the crucible.
Q6.
Calculate the amount of magnesium oxide in 7.56 g. Relative atomic masses: Mg = 24; O = 16.
7.56 mol
40 mol
Correct answer: 0.189 mol
5.29 mol
0.2 mol