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I Q1. The alcohol 2-methylpropan-2-ol, (CH3)3COH, reacts to form esters that are used as flavourings by the food industry. The alcohol can be oxidised to produce carbon dioxide and water. A student carried out an experiment on a pure sample of 2-methylpropan-2-ol to determine its enthalpy of combustion. A sample of the alcohol was placed into a spirit burner and positioned under a beaker containing 50 cm³ of water. The spirit burner was ignited and allowed to burn for several minutes before it was extinguished. The results for the experiment are shown in Table 1. Table 1 Initial temperature of the water/°C Final temperature of the water/°C Initial mass of spirit burner and alcohol/g Final mass of spirit burner and alcohol/g 18.1 45.4 208.80 208.58
(b) Calculate the amount, in moles, of 2-methylpropan-2-ol burned in the experiment. Hence calculate a value, in kJ mol-¹, for the enthalpy of combustion of 2-methylpropan-2-ol. Show your working. (If you were unable to calculate an answer to part (a), you should assume that the heat energy released was 5580 J. This is not the correct value.) (c) An equation for the combustion of 2-methylpropan-2-ol is (CH3)3COH(I) + 60₂(g) Table 2 contains some standard enthalpy of formation data. Table 2 AH/kJ mol 1 (CH3)3COH(I) -360 4CO2(g) + 5H₂O(1) O₂(g) 0 CO₂(g) -393 Use the data from Table 2 to calculate a value for the standard enthalpy of combustion of 2-methylpropan-2-ol. Show your working. H₂O(1) -286 (3)