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The energy released by an Homologous series of alcohols

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Introduction

The energy released by an Homologous series of alcohols In this investigation I am going to find out how the amount of energy released is affected by the number of carbon atoms in the alcohol. The table below shows some information about four member of the alkane family. Alkanes are saturated hydrocarbons. Alcohol Formula Structure Mass of 1 mole/g State at room temperature Methanol CH3OH 32 Liquid Ethane C2 H5 OH 46 Liquid Propane C3 H7OH 60 Liquid Butane C4 H9OH 74 Liquid Reactions of Hydrocarbons The hydrocarbons called alkanes are fairly unreactive. However, alkanes do burn well to produce energy. Most of the uses of alkanes rely on exothermic reactive when they burn. The combustion of hydrocarbons, including alkanes, requires oxygen from the air. Providing there is a plentiful supply of oxygen, the products are water vapour and carbon dioxide. If hydrocarbon, including alkanes, burn in a limited supply of oxygen, water vapour is still produced but the poisonous gas carbon monoxide, CO, can be produced. Measuring Energy released The following bond energies are in a KJ per mol. One mole of an alcohol contains 6x10-23 molecules. C-C = 347 C=C = 805 C-H = 413 O-H = 464. The number and types of bond on the left hand side of: CH3 OH + 11/2O2 CO2 + 2H2O C-H = 5 x 413 = 2065 C-C = 1 x 347 = 347 C-O = 1 x 358 = 358 O-H = 1 x 464 = 464 O=O= 3 x 498 = 1494 Total = 4728 KJ Right hand side: C=O = 4 x 805 = 3220 O-H = 6 x 464 = 2784 Total = 6004 KJ Overall energy charge = 6004 - 4728 = 1276 KJ/mole References: ...read more.

Middle

even setting up the equipment is to put on safety goggles as you will be dealing with extremely flammable and potentially dangerous substances. Once you have done that assemble equipment as in diagram above. If the spirit burner is not already set up, fill the spirit with 10 ml of the alcohol. But be careful when pouring in the alcohol into the burner, as it is very flammable, if you spill any onto you wash it off. Then weigh the spirit burner with the fuel and record it. Measure out 200 ml of cold tap and put it into the large copper container and clamp above the spirit burner. Take the temperature of the cold water. Then light the spirit burner and start the stopwatch. Measure the temperature of the water in the copper container every 30 seconds for 5 minutes. After 5 minutes put out the flame, and then measure the burner and record the mass. Repeat this two to three times. Then repeat for each alcohol. To make this experiment a fair test I repeated the experiment twice times to calculate an average. I also tried to keep all of the other variables the same, such as the material of the container, the time fuel burnt and so on. However, due to external factors I could not control the size of the wick on the fuel burner nor could I control the amount of spirit in the burner, as the alcohols were already prepared in different burner. However, this prevented contamination between two different alcohols, which allowed me to gain more accurate results, as there was no possibility of contamination. ...read more.

Conclusion

I also noted that Butanol burnt less fuel than the other alcohol, I am not sure whether that is down to the thickness of the wick on the spirit burner, or the fact the butanol has 4 carbon atoms, so it would require more energy to break them, as Carbon atoms are very large, and so have strong bonds between them. This might be able to explain why there is such a sudden surge of energy then such a drop in energy. Analysing the results of this experiment, you can see that the amount of energy transferred to the water increases as time goes on, which coincides with my prediction. However, the results I gathered to show which alcohol transferred the greatest amount of energy to the water, didn't not coincide with my prediction, as I predicted that that the alcohol with the greatest amount of carbons in its molecular structure. Instead the graph shows quite the opposite, however, I feel I can't come to an accurate scientific conclusion based on these results alone. I can't come to a conclusion with these results as the spirit burners for each alcohol were different and had different wick sizes, which probably affected the results, so all of this has to be taken into account. Due to this important factor I believe that from these results I can't make a solid scientific conclusion. There are also quite a few anomalous results that can be seen clearly in the graphs above. These results could be due varying amount of alcohol in the burner, and I only also tested each alcohol twice, maybe if I increased the amount of tests I performed on each alcohol to three times, maybe I would have been able to make a more accurate average. Evaluation Olivia Blain 11s ...read more.

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