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The aim of this experiment is to find the enthalpy change of combustion of a number of alcohols so that you can investigate how and why the enthalpy change is affected by the molecular structure of the alcohol.

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Introduction

Chemistry Coursework Robbie Lloyd Planning Introduction:- The enthalpy change of combustion of a fuel is a measure of the energy transferred when one mole of the 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 1�C. The aim of this experiment is to find the enthalpy change of combustion of a number of alcohols so that you can investigate how and why the enthalpy change is affected by the molecular structure of the alcohol. The apparatus to be used:- * Small copper can or other metal container to act as a calorimeter. * Thermometer that measures to 0.1�C. * 100cm3 measuring cylinder. * Spirit burners containing:- o Methanol o Ethanol o Propan-1-ol o Butan-1-ol * Balance * Bunsen burner * Wooden splint * Draught shielding * Clamp and stand * Water * Heat proof mat Equation for the combustion of alcohols:- Alcohol + Oxygen Water + Carbon dioxide E.g. Combustion of methanol CH3OH + O2 CO2 + 2H2O The method to be use for the experiment:- * To begin with prepare a table remove all items of stationary from the surface and place them in bags, leaving only the paper and pen that are to be used to record the results. ...read more.

Middle

* Reading the thermometer accurately to 0.05 degrees Celsius, and recording it on the prepared table below. Alcohol Temperature/ oC Mass of alcohol/g Mass of water/g Start End Start End Start End Methanol Ethanol Propan-1-ol Butan-1-ol * Before the fires are lit to avoid potential hazards due to open flames jackets should be removed, lab coats should be put safety goggles should be put on hair should be tied back. * Next light a splint, hold it in one hand, remove the lid and light the spirit burner, place the draught shield around the clamp stand and spirit burner. The draught shield is simply to ensure that the heat loss to the surroundings is minimal to ensure that the worked values for enthalpy of combustion are as accurate as the equipment in of an A level class room will allow. * The equipment should now be exactly as seen in diagram 1. * I have decided to have a change in temperature of 20oC. * As the water is being heated the thermometer should be used to stir the water. This to ensure that the temperature registering on the thermometer is uniform through out the water and will not rise or fall as the water settles once the heating stops. This is to ensure the temperature recorded in the temperature will be accurate. ...read more.

Conclusion

* This whole process including the two repeats for each of the other alcohols. Risk Assessment * The alcohols vapours are flammable at temperatures above 13 oC , so the lid must be kept on the spirit burner at all times to prevent a fire. * Alcohols (except methanol) produce narcotic effects if you inhale it, so the victims must be removed to a region of fresh air. * If the alcohols propanol and any of the higher alcohols are swallowed, the mouth must be washed out with water. * If the alcohol is spilt in eyes, flood the eyes with running tap water for ten minutes, and then seek medical attention. * If spilt on skin or clothing, remove contaminated clothing to prevent fire risk and wash the contaminated area. * If spilt in the lab, shut off all sources of ignition, open all windows, and apply the mineral absorbent. Safety * Wear lab coat and goggles, as the fuels dealt with in this experiment will be highly flammable. * Try to avoid the alcohol making contact with skin, eyes and mouth. * Do not breathe the vapours. * Do not open the spirit burner in a lab with naked flames. * Always keep the stoppers on the bottles when not in use, and keep the bottles well away from the open flames. Accuracy, Fair Test and Precision This information has been included in the method. The sources I have used in devising my plan:- o http://www.coursework.info/user.cgi o http://www.quantchem.kuleuven.ac.be/safety/liab12.htm o DF1.2 o Chemical Ideas ...read more.

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