Trichloromethane and propanone are both organic liquids. The molecules within each liquid are attracted to each other by relatively weak permanent dipole-dipole interactions. When trichloromethane is mixed with propanone a strong electrostatic attraction forms between the two different molecules. [Figure showing trichloromethane, propanone, and electrostatic attraction between them] A student plans to perform an experiment to investigate the strength of this electrostatic attraction by finding the temperature change when equal volumes of trichloromethane and propanone are mixed together.

1. (a)(i)State and explain your prediction for the temperature change for this experiment.[1]
2. (a)(ii)The student is given only the following equipment and chemicals for the experiment. 1 x 25 cm³ beaker 2 × thermometers 2 × 25 cm³ measuring cylinders 50 cm³ trichloromethane 50 cm³ propanone Outline the method the student should use in this one experiment to find the temperature change when trichloromethane is mixed with propanone. Give details of the volumes of liquids used and any readings taken. volumes used readings taken method used[3]
3. (b)The apparatus used leads to significant heat loss. State one improvement the student could make to the apparatus to reduce heat loss.[1]
4. (c)Trichloromethane and propanone are both volatile and flammable. State one relevant precaution that should be taken when carrying out this experiment.[1]
5. (d)State one change, apart from reducing heat loss, that could be made to improve the accuracy of this experiment.[1]
6. (e)(i)In another experiment, a student uses 37.50g of trichloromethane and 19.75g of propanone and determines that the energy released is 1.67kJ. Calculate the number of moles of each compound in this mixture. Mᵣ trichloromethane = 119.5 Mᵣ propanone = 58.0 moles of trichloromethane = .......................... mol moles of propanone = .......................... mol[1]
7. (e)(ii)Calculate the enthalpy change, ∆H, of the electrostatic attraction formed between trichloromethane and propanone. You must include a sign in your answer. ∆H = .......................... kJ mol⁻¹[2]
8. (f)Suggest an experiment the student could carry out to test whether the number of moles of trichloromethane affects the temperature change.[1]

This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.