Starter quiz
- Match the following terms to the correct definition.
- Oxidation⇔Reaction in which oxygen atoms bond to the elements of the reactants. ✓
- Limiting reactant⇔The reactant that completely reacts during a reaction. ✓
- In excess⇔A reactant that remains at the end of a reaction. ✓
- Molar ratio⇔How many moles of each chemical we need to react to make the products. ✓
- True of false? Combustion is an example of an oxidation reaction.
- True ✓
- False
- Which of the following equations describes an oxidation reaction?
- iron + sulfur → iron sulfide
- sulfur + oxygen → sulfur dioxide ✓
- copper carbonate → carbon dioxide + copper oxide
- sodium + bromine → sodium bromide
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- The formula for glucose is C₆H₁₂O₆. Which of the following statements about glucose are correct?
- The ratio of carbon to hydrogen is 2 : 1
- The ratio of oxygen to hydrogen is 1 : 2 ✓
- The ratio of carbon to oxygen is 1 : 1 ✓
- The ratio of hydrogen to carbon is 1 : 2
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- Which of the following are examples of oxidation reactions?
- CH₄ + 2O₂ → CO₂ + 2H₂O ✓
- CuO + H₂ → Cu + H₂O
- 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
- N₂ + 3H₂ → 2NH₃
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- What is the ratio of oxygen to carbon dioxide in the following equation? CH₄ + 2O₂ → CO₂ + 2H₂O
- 2 : 1 ✓
- 1 : 1
- 1 : 2
- 2 : 2
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Exit quiz
- Match the following terms to the correct definition.
- Stoichiometry⇔The molar ratio of the reactants and products in a chemical reaction. ✓
- Mole⇔The unit of substance. ✓
- Limiting reactant⇔Substance that completely reacts during a reaction. ✓
- Constant mass⇔The mass remains the same. ✓
- Which of the following is an example of a closed environment?
- Heating magnesium in a Bunsen burner flame.
- Heating magnesium in a beaker.
- Heating magnesium in a crucible with a lid. ✓
- Heating magnesium in an evaporating basin.
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- Which of the following are advantages of using a crucible and lid to heat magnesium?
- Potentially loses less product. ✓
- Is fast.
- Is easy to observe.
- Protects scientists from the bright light produced. ✓
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- 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
- 2.78 g ✓
- 4.78 g
- 9.56 g
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- When magnesium is heated in a crucible the lid is occasionally opened. This makes sure the oxygen ...
- is in excess. ✓
- is limiting.
- escapes the crucible.
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- Calculate the amount of magnesium oxide in 7.56 g. Relative atomic masses: Mg = 24; O = 16.
- 7.56 mol
- 40 mol
- 0.189 mol ✓
- 5.29 mol
- 0.2 mol
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Worksheet
Presentation
Video
Lesson Details
Key learning points
- Heating magnesium in a crucible will react it with oxygen.
- The crucible must be opened periodically to ensure enough oxygen enters the vessel to completely oxidise the magnesium.
- Opening the crucible too much will cause mass/product loss.
- Safety precautions should be taken when burning magnesium because of the bright light produced.
- 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