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# Chemistry Lab report (enthalpy changes)

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Introduction

Chemistry Lab-Report Planning A 1) Aim: To determine the enthalpy changes for three alcoholic fuels. 2) Background knowledge: Heat of combustion of a substance is defined as the amount of the heat liberated when one gram mole of the substance is completely burnt. It is measured in kilo calories. A known quantity of alcohol is made to burn and the heat liberated is used in raising the temperature of water the amount of heat liberated can be calculated, from which the heat of combustion of alcohol is calculated. 3) Hypothesis: 4) Variables: Planning B 5) Spirit lamps (with each of the fuels separately), copper Calorimeter with stirrer, retort stand with clamps, tripod stand, thermometer, windshield, measuring cylinder (100 ml) 6) +7) * Weigh the spirit lamp, containing the given amount of the alcoholic fuel accurately (including the flame cap). * Using a measuring cylinder, pour 100 ml. of water in the Calorimeter. * Keep the Calorimeter on a tripod stand, suspend the thermometer in water and record the initial temperature of water. ...read more.

Middle

Therefore, weight of water in the calorimeter = 100 g. * Water equivalent of calorimeter (given) = (W � 0.1) = 4.1 given Observations C C C M g 190.80 g 214.38 g 176.20 g M g 188.26 g 212.96 g 174.96 g (M -M ) g 2.54 g 1.42 g 1.24 g t �C 30�C 30�C 30�C t �C 60�C 60�C 60�C (t - t )�C 30�C 30�C 30�C Mass of water (g) 100 g 100 g 100g 9) Molecular weight of methyl alcohol (CH OH) = 32 Total heat evolved in combustion of methyl alcohol = Heat gained by calorimeter + Heat gained by water = (W � 0.1) � (t - t ) + 100 � (t - t ) = (t - t ) (W � 0.1 + 100 ) cals. = (60 - 30) (4.1 + 100) = (30 � 104.1) Q = 3123 cals. When (M - M ) g, Methyl alcohol burns heat evolved is = Q cals = 3123 calories. ...read more.

Conclusion

Therefore, heat of combustion of ethyl alcohol = 3123 � 46 cals 1.42 Thus, heat evolved = 101167.6056 cals = 101167.6056 K.cals/ mole = - 101.17 � 4.184 KJ/mole 1000 Heat of combustion of Ethyl alcohol = 101.17 -K cals/mole = -423.30 KJ/mole Molecular weight of Propane alcohol (CH CH CH OH) = 60 Total heat evolved in combustion of ethyl alcohol = Heat gained by calorimeter + Heat gained by water = (W � 0.1) � (t - t ) + 100 � (t - t ) = (t - t ) (W � 0.1 + 100 ) cals. = (60 - 30) (4.1 + 100) = (30 � 104.1) Q = 3123 cals When (M - M ) g, Propane alcohol burns heat evolved is = Q cals = 3123 calories. Therefore, 60 g of ethyl alcohol will evolve = Q � 60 cals (M - M ) Therefore, heat of combustion of propane alcohol = 3123 � 60 cals 1.24 Thus, heat evolved = 151112.9032 cals = 151112.9032 K.cals/ mole = - 151.11 � 4.184 KJ/mole 1000 Heat of combustion of Ethyl alcohol = 151.11 -K cals/mole = -632.26 KJ/mole ...read more.

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