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An Investigation to find out how and Why enthalpy change is affected By the molecular structure of alcohols

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Introduction

An Investigation to find out how and Why enthalpy change is affected By the molecular structure of alcohols The goal of this investigation is to ascertain the difference in enthalpy change of combustion for a variety of alcohols. From these differences, I will be able to deduce why and how enthalpy change is affected by different molecular structures. The enthalpy change of combustion of fuel is a measure of the energy transferred when one mole of fuel is completely combusted. To find out the enthalpy change of combustion for alcohols I am going to use the burning alcohol to heat a metal container filled with Water. Using the fact that Water (H2O) needs 4.2J of energy to raise the temperature of 1 gram of Water by 1 c. From prior Knowledge, I know that 1g of water is equal to 1ml of water. This investigation will have to be carried out in the delta H standard, which is completing the investigation in standard temperature(298K, or 25c), Standard pressure of one atmosphere and a standard concentration of 1 mol dm. To work out the enthalpy change you need the equation CM T. C is equal to the specific heating capacity of water (4.17Jg 1K 1). M is equal to the mass of water in grams. T is the temperature of water. For this investigation, I have chosen the following alcohols, Methanol, Ethanol, Propan-1-ol, Butan-1-ol and 2-Methylpropan-1-ol. ...read more.

Middle

* A clamp stand, this to hold the calorimeter above the flame away from the spirit burner. * Electronic weighing scales, This will allow a greater deal of accuracy when weighing the spirit burners. This will also help make it a fairer test as electronic scales are accurate to 2 decimal places. * Measuring Cylinder, This will give accurate measurements for water. When taking measurements they must be taken at eye level. * Thermometer, this is to help record the raise in water temperature. * Safety goggles, these are to be worn at all times to prevent anything from entering the eye. Risk Assessment (fig2) Methanol and Ethanol - These are both highly flammable. The vapour of these compounds catch fire above 13 centigrade. Inhalation of these alcohols has a narcotic effect on the body. If inhalation occurs, remove the victim to fresh air. If swallowed wash out mouth, and if victim shows drunk like symptoms consult a doctor. Propan-1-ol - This is highly flammable, harmful and an irritant. There is a serious risk to eyes with this compound so goggles must be worn at all times when handling it. If it gets in the eye, flood it with water and seek medical attention. If swallowed wash out mouth. If inhalation occurs, remove the victim to fresh air. Butanol-1-ol - This is flammable, harmful and an irritant. It is an irritant to the respiratory system, so if inhalation occurs seek medical attention. ...read more.

Conclusion

around the spirit burner and calorimeter to maximise the energy transfer between the spirit burner and the Calorimeter. Put the thermometer into the water and hold it there for a minute, not letting it touch the calorimeter and then record the start temperature. 7. Light the wick of the spirit burner, stir the water with the thermometer continuously. When the water has increased by 13c-15c replace the lid on the spirit burner, but keep the thermometer in the water still not letting it TOUCH the calorimeter for another two minutes as heat is still being transferred to the water from the calorimeter. Record the temperature after these two minutes. 8. Weigh the spirit burner again making sure the correct lid is put back on the burner, Record this weight in your results table. There are a number of variables to take into consideration when keeping the investigation fair these are; * Keeping the lid on the spirit burner when it is not being used so there is no loss of mass due to evaporation. * Cleaning the copper calorimeter in between each different spirit burner to stop soot build up. Soot build up on the calorimeter reduces the amount of energy which can be transferred to the water. * Another problem is trying to keep the temperature of the calorimeter the same each time the experiment is conducted. Extreme difference in temperature would result in a unfair test. * Another problem is that the water temperature rise is not going to be the same every time the experiment is conducted. ...read more.

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