To measure and compare the enthalpy change of combustion for four different types of fuels by burning them and measuring the increase in the temperature of water in a calorimeter.
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Chemistry Coursework Planning Aim: To measure and compare the enthalpy change of combustion for four different types of fuels by burning them and measuring the increase in the temperature of water in a calorimeter. From the increase in temperature of a known mass of water it is possible to calculate the enthalpy change of combustion (?Hc) for the fuels by the following formula Energy transfer = mass x Specific Heat Capacity x ?T joules Where ?T = the change in temperature in degrees Kelvin. The specific heat capacity of water is 4,2 J g-1 K-1 (Cambridge Chemistry 1). The specific heat capacity means the amount of energy required to raise 1 gram of water 1o C. The enthalpy change of combustion is when 1 mole of substance reacts completely with oxygen under standard conditions. Apparatus: > Small copper can which acts as a calorimeter, (base diameter 10cm). > 0-1100C thermometer > 100cm3 measuring cylinder > Spirit burners containing -methanol, ethanol, propan-1-ol and butan-1-ol. > Access to a weighing balance (2 d.p) > Draught shields Method: > Use 200 cm3 of cold water in a copper calorimeter and record its temperature. Measure the water volume using a burette because this as the smallest percentage error, of 0.175%. > Support the calorimeter over a spirit burner containing the fuel you are testing by using a clamp stand.
Treatment of results The results that will be gathered will be tabulated. Convert the volume of water to a mass by using the known density of water (1000 cm3 = 1000 gram). An average will be calculated making sure anomalies are left out. Then a calculation of the enthalpy change of combustion will be calculated using the formula. These will then be compared with the text book enthalpy change of combustion figures that have been obtained from Royal Society of Chemistry Electronic Databook 2002. Methanol = CH3OH, the enthalpy change of combustion = -726.0 kJ mol-1. Ethanol = CH3CH2OH, the enthalpy change of combustion = -1367.3 kJ mol-1 Propan-1-ol = CH3CH2CH2OH, the enthalpy change of combustion = -2021.0 kJ mol-1 Butan-1-ol = CH3(CH2)2CH2OH, the enthalpy change of combustion = -2675 kJ mol-1 Limitations The same equipment will be used for each experiment. The only things that will be changed are the two different types of fuels, along with the spirit burners that contain them. The room temperature cannot be changed easily. The room temperature is not significant to the outcome of the results. The starting temperature of the water is more important. The experiments could all be done on the same day to reduce temperature errors. The loss fuel cannot be stopped totally so when doing the experiment it is best to put the lids on the burners when they are not lit and measuring the mass of the burners as soon as they have finished heating the water.
> If spilt onto clothes or skin, then remove the contaminated clothing and wash the affected area > If spilt tin the laboratory then shut off all sources of ignition, open all windows and apply a mineral absorbent to the spill, then scoop into a bucket and add water Preliminary Results Preliminary work will be done to find out the problems that could occur and how they can be fixed. Preliminary work was obtained from the salter activity sheet DFI.2. During the preliminary work only one fuels will be tested. Methanol will be tested, as this is more volatile. Finding out where to hold the thermometer and where to stir in the calorimeter will also be achieved. Along with the distance of the flame to the calorimeter. This is important because it will reduce energy loss if the space between the calorimeter and the burner is narrowed. Making sure that the variables are within a measurable range will also be checked. By using 200cm3 of water it can be found out if it is too much or too little. Timing the experiment will also be done to see if the temperature rises to quickly so that the results cannot be taken down, or if it rises too slowly so that it takes to long to do 5 experiments for each fuel. The results of the preliminary work will be analysed and if it necessary the method could be changed.
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