The enthalpy change of combustion, ∆Hᶜ, of butane, C₄H₁₀, can be determined using the apparatus shown in Fig. 2.1. [Figure 2.1] The following steps are carried out. step 1 Use a 500 cm³ measuring cylinder to transfer 320 cm³ of water into a metal can. step 2 Place a thermometer into the water. Record the initial temperature of the water in the metal can. step 3 Weigh the gas container with burner and record the initial mass. step 4 Set up the apparatus as shown in Fig. 2.1. step 5 Light the burner and allow the flame to heat the water in the metal can for three minutes. step 6 Switch off the burner and record the maximum temperature reached. step 7 When cool, reweigh the gas container with burner and record the final mass. The results are shown in Table 2.1. Table 2.1 initial temperature of water/°C | maximum temperature of water/°C | change in temperature of water, ΔT/°C | initial mass of gas container with burner/g | final mass of gas container with burner/g | mass of butane burned/g ---|---|---|---|---|--- 19.3 | 76.6 | | 183.56 | 181.46 |

1. (a)Complete Table 2.1. Record your answers to the appropriate number of decimal places.[2]
2. (b)Use the relationship q = mc∆T to calculate the energy, q, in J, gained by the water. 1.00 cm³ of water has a mass of 1.00 g. q = .............................................. J[1]
3. (c)Calculate the enthalpy change of combustion, ∆Hᶜ, of butane, in kJ mol⁻¹. Give your answer to three significant figures. ∆Hᶜ = .............................................. kJ mol⁻¹[2]
4. (d)Without changing the apparatus, suggest what should be done in step 6 before recording the maximum temperature reached to improve the experimental procedure.[1]
5. (e)The 500 cm³ measuring cylinder has graduations every 5 cm³. Calculate the percentage error in the measurement of the volume of water. Show your working. percentage error = .............................................. %[1]
6. (f)A student suggests that the value calculated in (c) is different from the actual value of ∆Hᶜ of butane because of heat lost during the experiment. Suggest one change to the apparatus that would reduce the heat lost.[1]
7. (g)(i)The experiment was repeated but the burner was switched off after only two minutes. Suggest why this might contribute to a reduction in the accuracy of ∆Hᶜ of butane.[1]
8. (g)(ii)Suggest why this might contribute to an increase in the accuracy of ∆Hᶜ of butane.[1]

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