Sherbet sweets contain citric acid and sodium hydrogencarbonate. When sherbet dissolves on the tongue, these substances react and the mouth feels cold and fizzy.
Name the gas that causes the fizzing.
The reaction is endothermic. State what happens to the temperature of the tongue.
A reaction profile is drawn for this reaction. Compare the energy of the products with the energy of the reactants.
The table gives energy values from the reaction profile.
| Point on the reaction profile | Energy / kJ |
|---|---|
| reactants | 50 |
| highest point of the curve | 120 |
| products | 80 |
Calculate the activation energy for the reaction.
Calculate the overall energy change. State whether this energy is taken in or given out.
A student says, "Only endothermic reactions have an activation energy."
Explain why the student is wrong.
53 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.