Copper(II) oxide reacts with dilute sulfuric acid to form copper(II) sulfate and water. The word equation for this reaction is: copper(II) oxide + sulfuric acid → copper(II) sulfate + water. The balanced symbol equation for this reaction is: CuO + H₂SO₄ → CuSO₄ + H₂O. Explain what the balanced symbol equation tells us about this reaction that the word equation does not.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
The symbol equation shows the exact chemical formulae of the species involved, revealing the atoms and ions present (CuO, H₂SO₄, CuSO₄, H₂O). It also displays the stoichiometric ratio of the reactants and products – 1 : 1 : 1 : 1 – so we know how many moles of each combine. Furthermore, the equation is balanced, meaning the number of atoms of each element on the left equals that on the right, demonstrating conservation of mass. Finally, the symbols indicate the composition of each compound, showing which atoms are bonded together.
Examiner tips
- Use the symbol equation to point out the exact formulae and stoichiometry; mention the 1:1:1:1 ratio and that the equation is balanced. Highlight conservation of atoms and compound composition. Keep the answer concise and to the point.
Common mistakes
- Confusing the word equation with the symbol equation; forgetting to mention the 1:1:1:1 ratio; not noting that the equation is balanced and therefore conserves atoms.
Mark scheme (4 marks)
- The symbol equation shows the chemical formulae / actual atoms or ions present (whereas the word equation only gives names)
- The symbol equation shows the ratio in which reactants combine and products are formed (1 : 1 : 1 : 1 molar ratio here)
- The symbol equation shows the number of atoms of each element on both sides are equal / the equation is balanced, demonstrating conservation of atoms
- The symbol equation shows the number of atoms of each element within each compound / the composition of each compound
Key terms in this question
Related
- All Pearson Edexcel International GCSE Chemistry (4CH1) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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