A student investigates the enthalpy of combustion of three alcohols using a simple spirit burner to heat water in a metal calorimeter (aluminium can) with a lid. The can contains 200.0 g of water and is initially at 21.0°C for each trial. The burner is placed under the can at the same height each time and a draught shield is used. The water is stirred continuously and heated until the temperature rises by about 30°C. The student records the mass of the burner (with fuel) before and after heating and the final water temperature.
The student repeats each alcohol twice and obtains the following results.
| Alcohol | Trial | Initial mass of burner + fuel (g) | Final mass of burner + fuel (g) | Final water temperature (°C) |
|---|---|---|---|---|
| Methanol, \(\mathrm{CH_3OH}\) | 1 | 182.44 | 181.32 | 51.0 |
| Methanol, \(\mathrm{CH_3OH}\) | 2 | 181.32 | 180.25 | 50.6 |
| Ethanol, \(\mathrm{C_2H_5OH}\) | 1 | 176.10 | 174.80 | 51.8 |
| Ethanol, \(\mathrm{C_2H_5OH}\) | 2 | 174.80 | 173.58 | 51.5 |
| Propan-1-ol, \(\mathrm{C_3H_7OH}\) | 1 | 190.55 | 189.12 | 52.5 |
| Propan-1-ol, \(\mathrm{C_3H_7OH}\) | 2 | 189.12 | 187.74 | 52.2 |
Assume the specific heat capacity of water is \(c = 4.18\,\mathrm{J\,g^{-1}\,K^{-1}}\). Ignore the heat capacity of the can and lid unless instructed otherwise. Molar masses: \(M(\mathrm{CH_3OH}) = 32.0\,\mathrm{g\,mol^{-1}}\), \(M(\mathrm{C_2H_5OH}) = 46.0\,\mathrm{g\,mol^{-1}}\), \(M(\mathrm{C_3H_7OH}) = 60.0\,\mathrm{g\,mol^{-1}}\).
Using the mean heat absorbed by the water from part (a), calculate the experimental molar enthalpy of combustion, \(\Delta H_c\), for each alcohol in \(\mathrm{kJ\,mol^{-1}}\). Include the correct sign and show your working using the measured mass loss of fuel.
Marking your answer...
This may take a few seconds
Sign up for free to see your full marking breakdown and personalised study recommendations.
Create Free Account Log inThis is a free HSC HSC Chemistry practice question worth 6 marks, testing your understanding of Conduct a practical investigation to measure. It falls under Alcohols in Module 7: Module 7: Organic Chemistry. Submit your answer above to receive instant AI-powered marking and personalised feedback.
Students focus on the principles and applications of chemical synthesis in the field of organic chemistry. Current and future applications of chemistry include techniques to synthesise new substances – including pharmaceuticals, fuels and polymers – to meet the needs of society. Each class of organic compounds displays characteristic chemical properties and undergoes specific reactions based on the functional groups present. These reactions, including acid/base and oxidation reactions, are used to identify the class of an organic compound. In this module, students investigate the many classes of organic compounds and their characteristic chemical reactions. By considering the primary, secondary and tertiary structures of organic materials, students are provided with opportunities to gain an understanding of the properties of materials – including strength, density and biodegradability – and relate these to proteins, carbohydrates and synthetic polymers.
Inquiry question: How can alcohols be produced and what are their properties?
conduct a practical investigation to measure and reliably compare the enthalpy of combustion for a range of alcohols
StudyPulse has thousands of HSC Chemistry questions with full AI feedback, mark breakdowns, progress tracking, and study notes across every Content Point point including Conduct a practical investigation to measure.
