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Comparing The Enthalpy Changes Of Combustion Of Different Alcohols.

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Introduction

(6)~~**����*AnGeL*����**~~(6) Comparing The Enthalpy Changes Of Combustion Of Different Alcohols. Plan: Aim: The enthalpy change of combustion of a fuel is a measure of the energy transferred when one mole of fuel burns completely. A value for the enthalpy change can be obtained by using the burning fuel to heat water and using fact that 4.2j of energy are required to raise the temperature of 1g of water by 1oC. In this investigation my aim is to find the enthalpy change of combustion of a number of alcohols so that I can investigate how and why the enthalpy change is affected by the molecular structure of the alcohol. I am going to investigate the enthalpy change of combustion for the alcohol homologous series. I will investigate how alcohols with increasing number of carbons affect the enthalpy change when an alcohol goes under combustion. The energy that alcohols release when being used is called the enthalpy change of combustion. As I already know that alcohols are a series of organic compounds which all contain a -OH group. My Prediction: By using the knowledge that I already have I think that the alcohols with a larger number of carbon atoms within the molecule will have a greater alcohol change of combustion than the alcohols with less carbon atoms. So therefore I predict that as the molecular mass increases so does the enthalpy of combustion. The alcohols that I intend to use throughout this investigation are the following 6 alcohols: > Methanol - CH3OH solvent; fuel; manufacture of organic chemicals; denaturing ethanol straight chain alcohol. > Ethanol - (CH3CH2OH) ethyl alcohol; grain alcohol. A colorless, flammable liquid produced by fermentation of sugars. Straight chains. > Butane - CH3CH2CH2CH3, colourless, with a characteristic natural odor > Pentan-1-ol -straight chains alcohol. > Hexan-1-ol - straight chain alcohol. > Propan-1-ol - straight chain alcohol. Using the alcohols listed above I will measure the amount of energy produced by them when burnt in air. ...read more.

Middle

The blood stream can then transport the absorbed contaminants to other parts of the body. A small amount of inhalation of certain chemicals is not life threatening however, as the dose increases; the chemical begins to exert an effect. But, as the body is capable of repairing the damage that may have been done, the exposure in this range is without adverse consequences. At still higher doses, the intense exposure overwhelms the defense mechanisms causing irreversible damage. Finally, at even higher doses, the exposure can be fatal. The graph below shows this: Risk Assessment. The table below shows the risks of the 6 alcohols that I am going to use, it also shows how accidents can be avoided. Name of Chemical. Particular hazard. Risk. Action needed for accident prevention. Action that needs to be taken incase of an accident. Methanol Toxic Irritant to the eyes and mucous membranes. It can react vigorously with oxidising materials. Methanol possesses distinct narcotic properties. It is also a slight irritant to the mucous membranes. Its main toxic effect is exerted on the nervous system, particularly the optic nerves, which could eventually lead to blindness. Once absorbed by the body it is only very slowly eliminated and thus is regarded as an accumulative poison. It can react vigorously with other materials. Don't stay exposed too long with methanol and do not mix methanol with any other chemicals as it may react vigorously with them. Seek medical advice and take the person out of the room to fresh air immediately. Ethanol Highly Flammable Vapour may catch fire easily, also a risk of inhalation, even drinking the alcohol may cause narcotic effects. Keep containers closed and away from any naked flames, also warn users to use Ethanol in well-ventilated space. Cover the area to remove oxygen, use a fire extinguisher if necessary, remove everyone from the area and take them out to get fresh air. ...read more.

Conclusion

To reduce the amount of heat lost it is important to cover the water with foil, however this makes it difficult to stir properly which would give inaccurate results of enthalpy of combustion. So therefore in order to reduce these limitations it is important to stir the water properly and avoid tearing the foil as this will mean that heat is lost. Finally once the experiment is done and the burner has to be weighed it is important that the lid of the burner is put back on straight away, this is to ensure that no vapour is lost via evaporation. In order for my experiment to go well and to gain accurate results as I possibly could, it was important that I used draft shielding to reduce any heat from being lost into the surrounding areas. Errors: The errors that occurred in my investigation were only minor errors that didn't have a great affect on my overall results. The errors that did occur are shown below: Errors for hexanol: Errors due to mass readings: Start: 0.01/228.962=0.0000436 Finish: 0.01/228.064=0.000438 Errors due to temperature readings: 0.1/19=0.00526 Errors due to volume of water measurements: 1cm3/100cm3=0.01 Total percentage of errors due to equipments: 0.0000436+0.000438+0.00526+0.01*100=1.0% Errors for butan-1-ol: Errors due to mass readings: Start: 0.01/240.541=0.0000415 Finish: 0.01/239.364=0.0000417 Errors due to temperature readings: 0.1/20=0.005 Errors due to volume of water measurements: 1cm3/100cm3=0.01 Total percentage of errors due to equipment: 0.0000415+0.0000417+0.005+0.01*100=1.0% Errors for propan-1-ol: Errors due to mass readings: Start: 0.01/256.323=0.000039 Finish: 0.01/255.201=0.0000392 Errors due to temperature readings: 0.1/20=0.005 Errors due to volume of water measurements: 1cm3/100cm3=0.01 Total percentage of errors due to equipment: 0.000039+0.0000392+0.005+0.01*100=1.0% Errors for ethanol results: Errors for mass readings: Start: 0.01/183.114=0.0000546 Finish: 0.01/182.059=0.0000549 Errors due to temperature readings: 0.1/20=0.0005 Errors due to the volume of water measurements: 1cm3/100cm3=0.01 Total percentage of errors due to equipment: 0.0000546+0.0000549+ 0.0005+0.01*100=1.0% Errors for methanol results: Errors for mass reading: Start: 0.01/183.114=0.0000546 Finish: 0.01/182.059=0.0000549 Errors due to temperature readings: 0.1/19=0.00526 Errors due to volume of water measurements: 1cm3/100cm3=0.01 Total percentage error due to equipment: 0.0000546+0.0000549+0.00526+0.01*100=1. ...read more.

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