Q1. [2] medium thorough-understanding
In a chemical equation, conditions such as heat or a catalyst are written above or below the arrow rather than on the reactant or product side. What does the arrow in a chemical equation represent, and why is it more appropriate to show reaction conditions on the arrow?
Generated by claude-sonnet-4-6 · 2026-06-26 00:53 · grounding rag
Model Answer
The arrow in a chemical equation represents the direction of the reaction, showing that reactants (LHS) are converted into products (RHS).
Reaction conditions like heat or a catalyst are written above or below the arrow because they are not reactants or products — they only influence how the reaction proceeds. Placing them on the arrow keeps the equation accurate and uncluttered.
Source: Chapter 1, Section 1.1.2 Writing a Chemical Equation
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Explanation
- 1 mark for stating what the arrow represents (direction of reaction / conversion of reactants to products).
- 1 mark for explaining why conditions go on the arrow — they are neither reactants nor products, only facilitating factors.
- Use examples from the textbook (e.g., sunlight/chlorophyll written above/below the arrow in Eq. 1.12) to support if needed, but keep it brief for 2 marks.
- Avoid writing a long paragraph; examiners look for these two specific points clearly stated.