Starter quiz
- Given the relative atomic masses (Ar): C (12), O (16) Calculate the relative molecular mass (Mr) of carbon dioxide (CO₂).
- 44 ✓
- 28
- 192
- 0.75
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- What does the conservation of mass in a chemical reaction imply?
- Mass of products is always more than the mass of reactants.
- Mass of reactants is converted into energy.
- Mass of reactants equals mass of products. ✓
- Atoms are destroyed to conserve mass.
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- If 20g of sodium reacts fully with 15g of chlorine, how much sodium chloride is produced?
- '35 g' ✓
- For the equation __ N₂ + __ H₂ → __ NH₃, select the correct coefficients to balance it.
- 1, 3, 2 ✓
- 1, 2, 3
- 1, 3, 3
- 2, 3, 2
-
- What does the equation 2H₂ + O₂ → 2H₂O tell us?
- Two molecules of hydrogen react with two molecules of oxygen.
- Two molecules of hydrogen react with one molecule of oxygen. ✓
- One molecule of hydrogen reacts with one molecule of oxygen.
- Two molecules of water are decomposed into hydrogen and oxygen.
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- Given the relative atomic mass values (Ar): H (1), S (32), O (16) Calculate the relative formula mass (Mr) of sulfuric acid.
- '98' ✓
Exit quiz
- Match the following terms with their correct definitions:
- balanced symbol equation⇔describes the numbers of atoms taking part in a reaction ✓
- conservation of mass⇔in a chemical reaction mass is neither created nor destroyed ✓
- relative formula mass (RFM)⇔the sum of the relative atomic masses of all atoms in a formula ✓
- coefficient⇔the number placed in front of a formula in an equation ✓
- True or false? In a chemical reaction, the total mass of all the products can be different to the total mass of all the reactants
- True
- False ✓
- Balance the following equation: __ H₂ + __ O₂ → __ H₂O.
- H₂ + O₂ → H₂O
- H₂ + O → H₂O
- 2H₂ + O₂ → 2H₂O ✓
- 2H₂ + 2O₂ → 2H₂O
- 2H + O → H₂O
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- 2Mg + O₂ → 2MgO. Relative atomic mass (Ar): Mg (24), O (16). 48 g of magnesium reacts with excess oxygen. Calculate the mass of MgO produced.
- 40 g
- 80 g ✓
- 64 g
- 48 g
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- 2Na + Cl₂ → 2NaCl. Relative atomic mass (Ar): Na (23), Cl (35.5). 46 g of Na reacts with excess chlorine. Calculate the mass (g) of NaCl produced (3 s.f.).
- '117 g' ✓
- H₂ + SO₃ → H₂SO₄. Relative atomic mass (Ar): H (1), S (32), O (16). 8.0 g of SO₃ reacts with excess hydrogen. Calculate the mass (g) of H₂SO₄ produced (2 s.f.).
- '9.8 g' ✓
Worksheet
Presentation
Video
Lesson Details
Key learning points
- In a chemical reaction, the atoms in reactants are rearranged and are the same atoms that are in the products.
- The mass of products in a chemical reaction is equal to the mass of the reactants.
- The sum of the RFM of the reactants equals the sum of the RFM of the products, taking account of balancing coefficients.
Common misconception
Pupils struggle to recall the order of steps required to mathematically process the available information in order to answer the question.
Colour-coding the steps can help pupils remember how many steps are involved. Much practice and perseverance is needed to create and maintain the memory pathway of the mathematical processing.
Keywords
Balanced symbol equation - A balanced symbol equation represents a chemical reaction using symbols and coefficients to ensure that the number of atoms of each element is equal on both sides of the equation.
Conservation of mass - Conservation of mass means the total mass of the starting reactants equals the total mass of the products formed.
Relative formula mass - The relative formula mass (RFM or Mᵣ) of a substance is the sum of the relative atomic masses of all the atoms in its formula.
Coefficient - A coefficient is the number placed in front of a chemical formula to balance an equation; it multiplies all the atoms in the formula and shows the ratio of substances in a reaction.