Determination of the enthalpy change of combustion

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Chemistry Laboratory Report 5

Date: 4th, November, 2008

Topic: Determination of the enthalpy change of combustion

Objective: To determine the enthalpy change of combustion of a series of alcohols

Introduction

In this experiment, a measured mass of an alcohol is burnt and the heat released is transferred to a calorimeter made from an aluminium can. The heat capacity of the calorimeter is first determined by calibration with methanol of known enthalpy change of combustion (715 kJmol-1). From the rise in temperature of water in the calorimeter, the enthalpy change of combustion of ethanol and propan-1-ol can be calculated.

Heat capacitor of the calorimeter can be calculated by, where n is no. of moles of methanol and C is heat capacitor of calorimeter

Enthalpy change of combustion can be calculated by: ∆Ho[alcohol]

Results

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Discussion

-Calculations

No. of moles of methanol used = 1.7(12+4+16)

                         = 0.0531 mol

Heat capacity of the can = (-715 x 0.0531)(-20.6)

                    = 1.84 kJoC-1

No. of moles of ethanol used = 1.28(12x2 + 6 + 16)

= 0.02783 mol

Enthalpy change of combustion of ethanol = (-21.4x1.84)0.02783

= -1414.9 kJmol-1

No. of moles of propan-1-ol used = 1.27(12x3 + 8 + 16)

= 0.0212 mol

Enthalpy change of combustion of propan-1-ol = (-22.2x1.84)0.0212

        ...

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