• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Comparing the enthalpy changes of combustion of different alcohols.

Extracts from this document...

Introduction

Rebecca Winter November 2003 Plan Comparing the enthalpy changes of combustion of different alcohols I am going to investigate the enthalpy change of combustion of a number of alcohols. The enthalpy change of combustion of a fuel is a measure of the energy transferred when one mole of fuel burns completely under the stated conditions. Enthalpy is defined as the energy of reaction, or the heat energy associated with a chemical change. I will be investigating how and why the enthalpy change is affected by the molecular structure of the alcohol. Therefore, I will attempt to find how the number of carbon atoms that the alcohol contains affects the enthalpy change that occurs during the combustion of the alcohol. Alcohols are derived from alkanes by substituting an -OH group for an -H atom. They are a series of related organic molecules and have a general formula of: CnH2n+1OH, where 'n' is the number of carbon atoms present. Alcohols have physically and chemically similar properties due to the similarities in molecular structure, and the fact that they differ only in the length and structure of the hydrocarbon chain. In my investigation I will be dealing with the first five alcohols in the homologous series; Methanol, Ethanol, Propan-1-ol, Butan-1-ol and pentan-1-ol. I have chosen five alcohols as I feel that it is a suitable range that I can manage in the given time span including repeats. ...read more.

Middle

Record the initial mass or the spirit burner plus alcohol. NB do not take the lid off the spirit burner until you are ready to perform the investigation as he alcohol will evaporate and interfere with your results and safety issues are a concern * Place the spirit burner under the can (acting as a calorimeter) and light the wick. * Continuously stir water with the glass rod, constantly monitor the temperature rise on the thermometer. * As the final temperature approaches a rise of 20?C be prepared to extinguish the spirit burner. The temperature may continue to rise so this must be taken into consideration when extinguishing the spirit burner. * Record final mass of burner and alcohol using the same chemical balance as previously in the experiment. * Ensure that can is thoroughly washed before repeating the experiment and that all traces of carbon are removed. * Repeat experiment using all the other alcohols using the exact same method. NB: when repeating the experiment all equipment must be at it's original starting temperature to maintain constant conditions. As with any scientific experimentation I need to consider the possible hazards which may occur and do all that is possible to minimize the risks of these hazards occurring. Goggles must be worn and hair tied back throughout the investigation. ...read more.

Conclusion

If the initial temperature is too high, the water may reach boiling temperature and although energy would still be being released, I would not be able to monitor this with my equipment. A very important variable that I must monitor is the temperature rise. I must ensure that the temperature rises 20?C from its initial temperature. This is a difficult variable to maintain, as the temperature will continue to rise after the alcohol has been extinguished. However, I must attempt to maintain that the temperature rise is 20?C, correct to the nearest ?C with each alcohol and repeat reading. I will repeat the investigation with five different alcohols and will repeat each alcohol three times to establish and average enthalpy change. This will help to ensure that my results are precise. I must also ensure that I use alcohols with the -OH bond in the same position each time. I have chosen to use Propan-1-ol, Butan-1-ol and Pentan-1-ol and must keep this constant throughout my investigation. I have learnt previously that the bond energies between two atoms will vary accordingly to where in the molecule the pair of atoms is. For this reason it is important to keep constant the position of the -OH group. I must ensure that the experiment is performed under standard conditions. I.e. 298K (25?C), 1 atmosphere and a concentration of 1mol dm -3. If this condition is not kept at a constant, ?H will vary accordingly to the specific conditions. ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our AS and A Level 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

See related essaysSee related essays

Related AS and A Level Organic Chemistry essays

  1. Marked by a teacher

    Comparing the enthalpy changes of combustion of different alcohols

    3 star(s)

    0.84g 2. 0.87g 0.86g 15�C 15�C 15�C Methanol 1. 1.69g 2. 1.40g 1.55g 15.5�C 17�C 16�C Butan-1-ol 1. 0.67g 2. 0.74g 0.71g 15�C 15�C 15�C Propan-1-ol 1. 0.70g 2. 0.74g 0.72g 15�C 15�C 15�C Propan-2-ol 1. 1.02g 2. 1.25g 1.14g 18�C 19.5�C 19�C Calculations: Q = m x c x ?T Q= heat exchanged with the surroundings (J)

  2. The Relationship Between The Number of Carbon Atoms In An Alcohol And Its Standard ...

    of analysing, the figures for ?H has been multiplied by -1 in order to give a positive figure. * CONCLUSION The aim of this experiment was to try and discover if there was a correlation or any common pattern between the amount of carbon atoms in an alcohol and its standard enthalpy change of combustion (?H).

  1. Find the enthalpy change of combustion of a number of alcohol's' so that you ...

    The measurements * Mass of alcohol burned (g) * Temperature increase (oc) This will tell me what mass of alcohol is used during combustion to cause the temperature increase of 20oc in the water, I can then work out the energy released per mole and compare these values and see which has the highest enthalpy of combustion.

  2. Investigating the Enthalpy Changes of Combustion of Alcohols.

    Continue heating until the temperature has risen by about 15 - 20 �C. 6. Extinguish the burner. Keep stirring the water ad note the highest temperature reached. 7. Weigh the burner to see what mass of fuel has been burnt.

  1. Investigation of Some of the Properties of a Pair of Cis-Trans Isomers

    Data and Calculation A. Conversion of maleic acid to fumaric acid Mass of maleic acid + weighing bottle 8.7453g Mass of weighing bottle 4.6659g Mass of fumaric acid (28.082 - 26.547)= 1.535g Percentage yield 37.63% B. Comparison of the properties of the 2 isomers 1.

  2. F336- aspirin individual Investigation

    I will scale up the quantities shown in method 1 as I will need a sufficient amount to perform repeats which I am analysing the purity of aspirin. 5) I will need to increase the amounts stated within method two if I am to obtain a reasonable yield for my analytical methods.

  1. The aim of this experiment is to produce Aspirin. This is an estrification in ...

    This is an alkaline hydrolysis known as sponification. It is the reaction of an ester with sodium hydroxide to produce an alcohol and the sodium salt of the carboxylic acid of the ester. The purity of the re-crystallised aspirin was 96.76% compared with the purity of pure aspirin which was 97.56%.

  2. The aim of this experiment is to investigate the enthalpy change of combustion for ...

    Theoretical bond enthalpy calulations BOND (KJ/mol) H-H +436 C-C +350 C=C +610 C-H +410 O=O +496 O-H +460 C-O +360 C=O +740 Methanol CH3OH H H-C-O-H H CH3OH(l) + 1.5O2(g) CO2 (g) + 2H2O(g) =3(C-H) + C-O + O-H + 1.5(O=O)

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