Four powders, P, Q, R and S, are being compared for use in a flameless food heater. Equal volumes of the same solution are placed in insulated cups. A different powder is added to each cup, and there is enough solution to react with all of the powder.
| Powder | Mass of powder (g) | Temperature change (∘C^\circ\mathrm{C}∘C) |
|---|---|---|
| P | 4.0 | +8.0 |
| Q | 3.0 | +5.4 |
| R | 8.0 | +12.0 |
| S | 5.0 | -10.5 |
Which powder should be chosen for the heater, to give the greatest temperature increase for each gram used?
S
P
Q
R
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.