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Thermochemistry Lab

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Thermochemistry is the study of heat or energy from chemical reactions. Heat energy may be absorbed or released meaning the reaction is either endothermic or exothermic. Thermochemical reactions look at the heat in regards to the surroundings of the reaction to determine what type of reaction it is. The changes in heat are calculated by a calorimeter. Calorimeters calculate the change in heat by measuring the change in temperature and using the formula Q = mc ΔT, where Q is the heat of energy transferred, m is the mass of the calorimeter, c the specific heat of the calorimeter and ΔT being the change in temperature. This investigation looks at the combustion of alcohols and alkanes. Alkanes and alcohols are both hydrocarbons. Hydrocarbons are …show more content…

The results of each mixture were averaged out and the heat given out and the heat given off in KJ/g was measured by the heat formula Q = mc ΔT. The theoretical values were calculated using a mass fraction. The heat given off was measured using a calorimeter of water and how much heat it absorbed. The theoretical values were calculated by using a mass fraction. The prediction of this experiment was that the alkanes that had longer carbon chains would increase the amount of heat given off. However, the results did not follow this hypothesis. The average values of pentane and hexane had the highest amount of heat given off …show more content…

While hexane and octane had the lowest values of 15.4KJ/g for hexane and 10.44KJ/g for octane. This was in comparison to the average value of the control tests for pentanol which was 12.67KJ/g. Theses average values in comparison to the theoretical values of the tests are about half the value due to large percentage errors. These results reveal that the alkanes that have an odd number of carbon atoms in their chain released more heat than the alkanes with even numbers of carbon atoms in their chain. For example, pentane has 5 carbon atoms in its chain has a higher value than hexane which has 6 carbon atoms in its chain. The cause of this may be due to something called the Odd -Even Effect. This effect explains how even numbers of carbon atoms in the chain pack tighter together forming a crystal lattice, meaning that they have a higher melting point than odd numbered carbon chains. It also means that there is a difference between the temperature and vapor pressure relationship within even and odd numbered carbon chains. This odd even effect may somehow link to the combustion of alkanes and explain the results and why they did not follow the hypothesis. The results of this

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