• Join over 1.2 million students every month
• Accelerate your learning by 29%
• Unlimited access from just £6.99 per month
Page
1. 1
1
2. 2
2
3. 3
3
4. 4
4
5. 5
5
6. 6
6
7. 7
7
8. 8
8
9. 9
9
10. 10
10
11. 11
11
12. 12
12

# An Investigation into the Enthalpies of the Combustion of Alcohols.

Extracts from this document...

Introduction

An Investigation into the Enthalpies of the Combustion of Alcohols Planning My aim for this experiment is to see the energy produced from different alcohols. This investigation involves burning alcohol in the air. 'GCSE Chemistry' by B.Earl and L.D.R Wilford says that "alcohols form, another homologous series, with the general formula Cn H2n+1OH ". The alcohol reacts with the oxygen in the air to form the products water and carbon dioxide. This reaction is exothermic, as heat is given out. This is because the amount reactant energy is more than the product energy the difference between this is ?H, therefore some energy has been given out in the form of heat. The energy is given out when forming the bonds between the new water and carbon dioxide molecules. This can be shown in an energy level diagram: Reaction co-ordinate ?H is the heat content, which is the enthalpy, which is negative in exothermic reactions as the diagram shows that energy is 'lost' as heat. Enthalpy is defined as the energy of reaction, or the heat energy associated with a chemical change. For any reaction carried out directly at a constant pressure, the heat flow is exactly equal to the difference between enthalpy of products and that of the reactants. To measure the heat energy given off, we must use this energy to heat something, this will be water. This is assuming that all the heat produced by combustion of the alcohol will equal the amount of heat absorbed by the water (q). So I will measure the amount of energy required to do so. This can be worked out by using the formula: q = mass x specific heat capacity x temperature rise or q = MC?H. Where q is the quantity of heat. The specific heat capacity is the amount of energy required to heat the substance, and is calculated using the formula: q =energy supplied/ Mass x Temperature, where q is the enthalpy, c is the specific heat capacity and ?H is the temperature rise. ...read more.

Middle

� Bunsen burner, � Retort stand, � Clamp, � Weighing balance Diagram Safety procedures � Make sure goggles and lab coat are worn through out the whole experiment, � Be ware of the hot water in the calorimeter, � Make sure copper calorimeter is tied tightly to the metal rod, � Make sure alcohol is lit safely with your selves rolled up out of the way, � Make sure the sprit lamp is put out by putting on the glass top after use. Method: I plan to carry out this experiment by using all the safety issues and fair testing procedures to give me the most reliable and most accurate set of results on each alcohol. I plan to record the mass of the alcohol sprit lamp before the experiment and after, which would tell me how much alcohol was used in each experiment, which I can compare to other alcohols. I will place 100cm3 of tap water into the copper calorimeter and clamp it to the retort stand; I will then hold the thermometer in the centre of the water in the calorimeter recording just the water temperature. This will give the most accurate set of results as the thermometer will not touch the copper calorimeter at all therefore only recording water temperature and not the calorimeters. I will then light the sprit lamp with a wooden splint wearing my safety glasses, and making sure the tip of the flame reaches the calorimeter flask at the same time will be starting the stop clock. Then I will then let the alcohol burn until the temperature has risen by 20oC for each alcohol, then it will immediately be put out and weighed. I will then record the finishing temperature of the water as the water will still be heated by the conduction of the copper calorimeter. I will then do the same thing for each alcohol and repeat, giving me the most reliable and accurate results, also ruling out any potential anomalies. ...read more.

Conclusion

The Propanol alcohol should have produce a heat energy between the alcohols Ethanol and Pentanol as Pentanol has 5 carbon atoms and ethanol has 2, where as Propanol has 3 making the results in between the two. The odd result of the Propanol alcohol could have been an anomalous result for a number of reasons. It could have been because the tip of the flame might have not been touching the bottom of the copper calorimeter, making the alcohol produce less heat to the water in the calorimeter. It could have also been because of the flame as it might have been too small, which might have also gave a low temperature reading to heat the 100cm3 of water. The procedure of the experiment was good enough of finding out the energy gained from the individual alcohols, but changes could have been made to make the reliability of the results more accurate. This could have been done by using a better and more accurate thermometer, such as an electric thermometer, which have gave me a much more pin point set of results. If I were to do this experiment again I would make a number of improvements or changes, I could use a Bomb Calorimeter which submerges the reaction inside an insulated container of water. An electrical heating device starts the reaction inside a sealed reaction vessel and the temperature rise of the water which surrounds it is measured. Bomb calorimeters are often used to find the calorific value of foods. Looking at the experiment I did I thought we could have extended the results we achieved by using different flame lengths, this would have told us how much the alcohol uses its energy when the flame is increased. I could have also changed the amount of water in the copper calorimeter, or even change the concentration of alcohol to see the effect. Parag Raval 11AC Chemistry Coursework ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our GCSE Organic Chemistry section.

## Found what you're looking for?

• Start learning 29% faster today
• 150,000+ documents available
• Just £6.99 a month

Not the one? Search for your essay title...
• Join over 1.2 million students every month
• Accelerate your learning by 29%
• Unlimited access from just £6.99 per month

# Related GCSE Organic Chemistry essays

1. ## Experiment to investigate the heat of combustion of alcohols.

4 star(s)

indicates that you will need 412 joules to break a Carbon - Hydrogen bond. I have calculated the energy change for each alcohol, using the bond energies already given above: Methanol CH3 OH + 1.5O2 CO2 + 2H2O Bond Breaking Bond Making 3 (C - H)

2. ## Titration experiment - write up

The volumetric flask has a percentage error of 0.24%. During my experiment I made sure to shake the volumetric flask, so that, I could ensure that the standard solution was mixed thoroughly. In addition if the equipment was not properly cleaned then my solution would have been contaminated resulting in inaccurate results.

1. ## The Combustion of Alcohols and the factors affecting these reactions

Then the difference between the mass before and after the alcohol was burnt was calculated and recorded. * The experiment was then repeated thee times for each of the five alcohols. Diagram of apparatus: When considering accuracy, measurements will be taken from a suitable level of accuracy.

2. ## To determine which alcohol, out of ethanol and propanol, is the better fuel. By ...

This is because the potential energy of a fuel increase as the carbon atoms increase, thus when released the energy value per gram will be greater. I can use the enthalpy change of combustion value of methanol and butanol in relation to my prediction.

1. ## Investigating the Combustion of Alcohols

would expect the heat of combustion to get larger as we go down the homologous series of alcohols because more molecules of CO2 and H2O are formed. Since the enthalpy change is negative I would expect the values to become more negative down the group.

2. ## Combustion of Alcohols

insulator and slow down the rate of heat transfer to the container and the water. Therefore, it must be wiped off the bottom of the calorimeter. * DISTANCE BETWEEN BUNSEN AND CALORIMETER - I will keep the distance between the Bunsen Burner and the calorimeter at 5cm.

1. ## Determination of the heat of combustion of alcohols

250cm3 = 250g Given: the standard heat of combustion of methanol = -715kJmol-1 The heat capacity of calorimeter = C The mole of Methanol = 1.95g / 12 + (1)(4) + 16 = 0.060 mol E=mc?T (715)(0.060)=(250/1000 x 4.2+heat capacity of calorimeter)(20)

2. ## Comparing the enthalpy changes of combustion of different alcohols.

affect my results by the time taken for the temperature rise of 15�C to be obtained, although it would be interesting to study. My independent variable is the alcohol, as these are substances that I will be changing throughout the experiment.

• Over 160,000 pieces
of student written work
• Annotated by
experienced teachers
• Ideas and feedback to