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Investigating how much energy is produced when burning alcohols.

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Introduction

-1- Jack Mariner Chemistry Coursework 2 Investigating how much energy is produced when burning alcohols. In this investigation I will be burning alcohols to heat up a beaker of water. I will be burning Methanol, Ethanol, Propanol, Butanol and Pentanol. Aim The aim is to find out how much energy is produced when burning these alcohols. 'An alcohol is a series of organic homologous compounds, with the general formula: Cn H n + 1OH' Alcohols react with oxygen in the air to form water and carbon dioxide. The reaction that is involved in burning alcohols is exothermic because heat is given out. The energy is given out when forming the bonds between the new water and carbon dioxide molecules. The amount of energy produced by such exothermic reactions can be calculated by using the formula: Mass of the substance x rise in temp x SHC (specific heat capacity) The specific heat capacity is the number of joules required to heat one gram of water by 1�C. I chose to use water because it is safe, easily found, and has a reliable specific heat capacity of 4.2. The bonds that are formed in an exothermic reaction can be of two types. The first could be ionic, where a metal is produced. ...read more.

Middle

From these results we can work out the total energy given out per mole for each alcohol. Methanol- CH3OH Energy given out= mass of water x SHC x temperature change (Joules) (100g) (4.2) (25) = 10,500J So if 1.61g of methanol gives 10,500J Then 1g of methanol (32g) gives: 10500 1.61 X 32 =208KJ So for methanol the total amount of energy given out per mole is 208KJ. Ethanol- C2H5OH So if 1.40g of ethanol gives 10,500J Then 1g of ethanol (46g) gives: 10500 1.40 x 46 = 345KJ So for ethanol the total amount of energy given out per mole is 345KJ. Propanol- C3H7OH So if 0.75g of propanol gives 10,500J Then 1g of propanol (60g) gives: 10500 0.75 x 60 = 840KJ So for Propanol the total amount of energy given out per mole is 840KJ. -6- Jack Mariner Chemistry Coursework 2 Butanol- C4H9OH So if 0.88g of Butanol gives 10,500 J Then 1g of butanol (74g) gives: 10500 0.88 x 74 = 883KJ (to 3 s.f) So for Butanol the total amount of energy given out per mole is 883KJ. Pentanol- C5H11OH So if 2.95g of pentanol gives 10,500 J Then 1g of pentanol (88g) ...read more.

Conclusion

The plan was followed very well and the results were of good quality. The measurements were done accurately, and a fair test was achieved. The procedure used was also a very fair and efficient one. Although the experiment was a success, I am still bothered by the fact that anomalous results occured in my experiment. I think that the reasons for these results were because of time limitations and careless mistakes. We had very little time to accomplish this task successfully, so mistakes were inevitable. The improvements, which could be made in doing this experiment, are to have a longer time to do the experiment so that isn't done making careless mistake and if mistakes were made, there would be enough time to redo what was needed. Secondly more high tech equipment could be used to get more reliable and accurate results. Conclusion From 'table 2', you can see that my hypothesis is of high quality stating that 'as the amount of atoms in the alcohols increase, so will the amount of energy per mole'. This was a perfect prediction. Thus for my conclusion, I conclude that 'As the amount of atoms in the alcohol increases, so does the total amount of energy per mole.' This is the case in my results excluding any anomalous ones. Which is why this wasn't reflected as strongly as it should've been. ...read more.

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