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Is there a relation between the structure of different alcohols and the energy release when burn?

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Mariano Bacigalupi 17/11/02 Group four chemistry practical Energy practical Is there a relation between the structure of different alcohols and the energy release when burn? Aim The aim of this experiment is to determine if the energy release data collected from different alcohols in a simple calorimeter has any relation which their atomic structure. Hypothesis The longer the molecule and the bigger the atoms on the molecule of the alcohol the more energy it will have. The method use to get the require data The first thin that needs to be done is to measure the heat capacity of the calorimeter that is going to be used. Put together a calorimeter as in fig. 1. Measure a fix amount of water (like as I used my case 270 g). Use an alcohol with a now heat capacity. Put the alcohol in a burner and light it wait until you got a steady flame on the burner. Empty the burner. Then measure the mass of the alcohol that is going to be used to get the heat capacity of the calorimeter. ...read more.


C= (1317*3.19)/(46*270*34) C=4003.68/422280 C=0.00995 This is going to be the value used of C in the equation so more accurate results are obtained for the experiment. By using this value of C we are taking in account the heat resistance of water and the heat resistance of the calorimeter also this is why the results are going to be more accurate. Experiment results chart Butanol Propanol Ethanol Starting temperature (�C) 22.5 22.0 20.0 Final temperature (�C) 54.0 54.0 54.0 Mass of the alcohol at the beginning (g) 2.98 3.25 6.24 Mass of the alcohol left at the end (g) 1.23 1.67 3.20 Difference in the mass (g) 1.75 1.58 3.04 Energy in the alcohols (KJ mol-1) 7822 7136 3021 Chart 2 Energy calculations Butanol Energy=(590.18*0.00995*31.5)/(1.75/74) Energy=7822 KJ mol-1 Propanol Energy=(590.18*0.00995*32)/(1.58/60) Energy= 7136 KJ mol-1 Ethanol Energy=8590.18*0.00995*34)/(3.04/46) Energy=3021 KJ mol-1 Energy data bar chart Graph 1 Graph 1 has a limitation that is that the number of decimal points used to make it does not allow reading it properly and if the number of decimal points allowed on Graph 1 is increase it's impossible to read team. ...read more.


More data of more alcohols could be used to determine if there could be a relation or a pattern between the alcohols and their structure. Conclusion As it can be seen from the results the bigger the molecule the more energy that it release when its burn, this is because the Van der Waals forces between the alcohol molecules increases as the molecule gets lager and in gains mass. So the stronger the Van der Walls forces between the alcohol molecules the more energy they release when the combust. These molecules are very similar to each other so it's easy to notice which molecule is going to release more energy. The amount of bonds in the molecule also affects the energy that they can release in combustion, so the more carbon hydrogen bonds the molecule was the more energy that it will release in combustion. All this factors that affect the energy that this molecules release can be easily seen in Graph 1 and 2. Finally in Graph 3 the number of carbon-hydrogen bonds and the energy release by the three alcohols tested can be seen and a pattern appears the more carbon and hydrogen atoms the molecule has the more energy that is release when burn. ...read more.

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