A student mixes citric acid solution with sodium hydrogencarbonate solution.
The student repeats the reaction using the same volumes and concentrations. The solutions start at 20.0 ∘C20.0\ ^{\circ}\text{C}20.0 ∘C each time.
| Container | Lowest temperature in ∘C^{\circ}\text{C}∘C |
|---|---|
| Open glass beaker | 17.0 |
| Polystyrene cup with a lid | 15.0 |
Why does the mixture reach a lower temperature in the polystyrene cup with a lid?
The cup and lid make the temperature the same throughout the mixture.
The cup and lid reduce the amount of citric acid that reacts.
The cup and lid transfer energy from the cooling mixture to the room.
The cup and lid reduce energy transfer from the room to the cooling mixture.
106 exam-style questions on OCR GCSE Chemistry 3.2 Energetics, covering 3.2.1 Exothermic and endothermic reactions and reaction profiles and 3.2.2 Calculating energy change from bond energies. Each one has a worked solution and a mark scheme showing where the marks go.