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My investigation is based around the subject of alcohols. The majority of people most commonly know alcohol as being a drink, which is consumed by many socially and is thought to be relaxing, but it actually acts a depressant.

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Introduction

Introduction My investigation is based around the subject of alcohols. The majority of people most commonly know alcohol as being a drink, which is consumed by many socially and is thought to be relaxing, but it actually acts a depressant. However in this investigation I am most interested in the chemistry side of alcohols. Alcohols in chemistry form a homologous series of compounds, which means they all have a general formula. They are generally referred to as being the -OH group, which is the functional group of an alcohol. This means that each alcohol contains an -OH bond. The -OH bond shown in the structural formulae determines the types of reactions created by that particular compound. The table below shows the first six alcohols in the series: NAME MOLECULAR FORMULA STRUCTURAL FORMULA Methanol CH3OH H H -C-O-H H Ethanol C2H5OH H H H-C-C-O-H H H Propanol C3H7OH H H H H-C-C-C-O-H H H H Butanol C4H9OH H H H H H-C-C-C-C-O-H H H H H Pentanol C5H11OH H H H H H H-C-C-C-C-C-O-H H H H H H Hexanol C6H13OH H H H H H H H-C-C-C-C-C-C-O-H H H H H H H The members in the series are similar in both physical properties and chemical reactions. ...read more.

Middle

Energy needed to break bonds Energy released when new bonds are formed Reactants Heat Change (KJ/mole) Products This energy level diagram shows an example of an exothermic reaction, where the energy released is higher than the energy needed to break the initial bonds. The heat of combustion is therefore shown by the heat change the reactants required to form the products (in Kilojoules per mole). In this instance, the products would become more stable because energy has been lost. Burning Alcohols Here is an equation to show what happens when an alcohol is burnt in the presence of oxygen: e.g. Ethanol C2H5OH (l) + O2 (g) 2CO2 (g) + 3H2O (l) This equation shows us that carbon dioxide (CO2) and water (H2O) are formed when the ethanol is burnt, and this is true for all alcohols. The products will always be CO2 and H2O but obviously varying in the amounts produced. This process is called complete combustion because all of the carbon (C) is converted into CO2 and all of the hydrogen (H) ...read more.

Conclusion

for the heat of combustion of ethanol: C2H5OH + 2O2 2CO2 + 3H2O ETHANOL OXYGEN CARBON WATER DIOXIDE This equation is balanced, so I will now work out the total bond energy values for each compound, using their structural formulas. Here are the reactant's totals: ETHANOL H H H - C - C - O - H H H 5 C - H = 5 x 413 = 2065 KJ 1 C - C = 1 x 347 = 347 KJ 1 C - O = 1 x 336 = 336 KJ 1 O - H = 1 x 464 = 464 KJ 3212 KJ/mole OXYGEN O = O O = O 2 O = O = 2 x 498 = 996 KJ 996 KJ/mole TOTAL OF REACTANTS = 3212 + 996 4208 KJ/mole The following calculations are for the products from the equation: CARBON DIOXIDE O = C = O O = C = O 4 C = O bonds = 4 x 805 = 3220KJ 3220KJ/mole WATER O H H 2 O - H bonds = 2 x 464 = 928KJ 928KJ/mole TOTAL OF PRODUCTS = 3220 + 928 4148KJ/mole ...read more.

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