Fig. 1.1 shows the apparatus you must assemble for this experiment. You are provided with solution F, aqueous copper(II) sulfate of concentration 0.200 mol/...

This is a calorimetry experiment on the displacement of copper by magnesium, \( \text{Mg} + \text{CuSO}_4 \rightarrow \text{MgSO}_4 + \text{Cu} \). The polystyrene cup, lid and stirrer are all there to trap the heat and mix the contents so the thermometer reads the true maximum temperature. Readings are quoted to the nearest \(0.5\,^\circ\text{C}\), the precision stated in the method.

(a) Record the steady starting temperature to the nearest \(0.5\,^\circ\text{C}\), typically in the range \(19.0\) to \(22.0\,^\circ\text{C}\); take \(20.5\,^\circ\text{C}\) as a worked value [1].

(b) Record the highest temperature reached, to the same precision, about \(15\) to \(18\,^\circ\text{C}\) above the start; take \(37.0\,^\circ\text{C}\) [1].

(c) The temperature rise is the maximum minus the start: \[ 37.0 - 20.5 = 16.5\,^\circ\text{C} \] marked from your own two readings (consequential) [1].

(d) Any two observations during the reaction [2]: the blue colour fades towards colourless or very pale; a brown or red-brown solid (copper) forms; bubbles of gas are seen; the grey magnesium powder disappears; the outside of the cup feels warm.

(e) The two products are copper [1] and magnesium sulfate [1]. The more reactive magnesium displaces the less reactive copper from copper(II) sulfate solution.

(f) The lid traps the warm air and cuts the heat lost from the open top of the cup, so the maximum temperature measured is closer to the true value [1].

(g) Stirring with the thermometer risks breaking the delicate bulb, or lifting it clear of the liquid, either of which would give a false reading; the stirrer is used instead [1].

(h) The reaction is exothermic [1]; the evidence is that the temperature of the mixture rose, so energy was given out to the surroundings [1].

(i) Powder has a much larger surface area than the same mass of ribbon [1]; so more magnesium particles are in contact with the solution, giving more frequent collisions, a faster reaction and the same energy released in a shorter time, hence a faster temperature rise [1].

(j) To test whether the rise depends on the concentration of copper(II) sulfate:

1. repeat with the same \(50.0\,\text{cm}^3\) volume and the same \(0.60\,\text{g}\) of magnesium powder, but with copper(II) sulfate of several concentrations, for example \(0.050\), \(0.100\), \(0.150\) and \(0.200\,\text{mol/dm}^3\) [1];
2. measure the start and maximum temperatures each time and calculate the rise [1];
3. keep the cup, lid, stirring and mass of magnesium the same (the controlled variables) and record the results in a table [1].

(k) One remaining loss: heat passes into the thermometer, the stirrer and the cup itself, warm vapour escapes through the hole in the lid, or heat is conducted through the base [1]. One improvement: pack cotton wool or a second cup around the first, or use a smaller hole in the lid [1].