The table gives energy values read from the reaction profiles of four reactions.
| Reaction | Energy of reactants / kJ mol−1\mathrm{kJ\,mol^{-1}}kJmol−1 | Energy at top of barrier / kJ mol−1\mathrm{kJ\,mol^{-1}}kJmol−1 | Energy of products / kJ mol−1\mathrm{kJ\,mol^{-1}}kJmol−1 |
|---|---|---|---|
| W | 110 | 160 | 40 |
| X | 50 | 170 | 130 |
| Y | 90 | 150 | 30 |
| Z | 120 | 210 | 150 |
Which of the endothermic reactions in the table has the smallest activation energy?
W
X
Y
Z
94 exam-style questions on Edexcel GCSE Chemistry 8.2 Heat energy changes in chemical reactions, covering 8.2.1 Exothermic and endothermic changes, 8.2.2 Bond breaking, bond making and overall energy change, 8.2.3 Calculating energy change from bond energies, and 8.2.4 Activation energy and reaction profiles. Each one has a worked solution and a mark scheme showing where the marks go.