A student investigated the temperature change during the endothermic reaction between citric acid solution and solid sodium hydrogencarbonate (NaHCO3\text{NaHCO}_3NaHCO3) in a glass beaker.
The student added portions of 3.0 g3.0\text{ g}3.0 g of sodium hydrogencarbonate to 25 cm325\text{ cm}^325 cm3 of citric acid solution and recorded the temperature after each addition. The results are shown in the table below:
| Mass of NaHCO3\text{NaHCO}_3NaHCO3 added (g\text{g}g) | Temperature (∘C^\circ\text{C}∘C) |
|---|---|
| 3.0 | 18.2 |
| 6.0 | 16.8 |
| 9.0 | 15.4 |
| 12.0 | 14.0 |
| 15.0 | 12.6 |
| 18.0 | 11.2 |
The recorded temperatures follow a linear relationship.
Name a container the student could use instead of a glass beaker to minimize heat transfer with the surroundings and improve the accuracy of the results.
The starting temperature of the citric acid solution corresponds to the yyy-intercept of the line of best fit (where the mass of sodium hydrogencarbonate added is 0 g0\text{ g}0 g). Determine this starting temperature in ∘C^\circ\text{C}∘C.
13 exam-style questions on AQA GCSE Chemistry 5.1 Exothermic and endothermic reactions, covering 5.1.1 Energy transfer during exothermic and endothermic reactions, 5.1.2 Reaction profiles, and 5.1.3 The energy change of reactions (HT only). Each one has a worked solution and a mark scheme showing where the marks go.