Brainlag PlusEnergy level diagrams, activation energy, the sign of ΔH and what a catalyst changes.
Up the hill, then down
A reaction profile shows the energy of the reactants, the products, and the hump in between.
- Activation energy: the minimum energy colliding particles need to react. It is the height of the hump above the reactants.
- ΔH (overall energy change) = energy of products − energy of reactants. Negative for exothermic (products lower), positive for endothermic.
- reactants 200 kJ/mol, peak 320 kJ/mol, products 120 kJ/mol
- activation energy = 320 − 200 = 120 kJ/mol
- ΔH = 120 − 200 = −80 kJ/mol: exothermic
The rest of this lesson and its 10 practice questions are in Plus.
Screen 1 of 2, free to read.
- 10 exam-style questions, marked as you go, each with a worked solution
- Anything you get wrong is saved to your flashcards