Topic 1 · 8.1–8.3 · Free
Topic Notes · Easy summaries with diagrams
Chapter 8 — chapter 8
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📘Easy summary
Macroscopic properties are those we can observe or measure (colour, pressure, concentration, temperature). Microscopic events are what particles are doing (molecules reacting, dissolving, evaporating). A reversible reaction proceeds in both directions: reactants form products (forward) and products re-form reactants (backward), shown by ⇌, e.g. H₂ + I₂ ⇌ 2HI, N₂ + 3H₂ ⇌ 2NH₃. Irreversible reactions go only one way (burning). At the start the forward rate is maximum; as reactants are used up their concentration falls so the forward rate slows down, while the backward rate increases as products build up. When both rates become equal, macroscopic properties stay constant even though microscopic changes continue — chemical equilibrium.
⭐Key points
- Reversible: ⇌.
- Forward rate falls, backward rate rises.
- Equilibrium: rates equal.
🔬Diagram
🌿Real-life example
In a sealed bottle of soda, CO₂ dissolves and escapes at equal rates.
💡Exam tip
- Use rates, not amounts, to define equilibrium.
✅Quick check
1. At equilibrium:
2. Forward rate slows near equilibrium because:
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