Enthalpy Change

We are required to calculate the standard enthalpy of combustion of Cyclopropane. The standard enthalpy of combustion is the heat released when 1 mole of a substance completely reacts with oxygen under standard conditions. The combustion reaction for Cyclopropane (

%5Ctext%7BC%7D_3%5Ctext%7BH%7D_6

) can be written as:

%5Ctext%7BC%7D_3%5Ctext%7BH%7D_6(g)%20%2B%20%5Ctext%7BO%7D_2(g)%20%5Crightarrow%203%20%5C%2C%20%5Ctext%7BCO%7D_2(g)%20%2B%203%20%5C%2C%20%5Ctext%7BH%7D_2%5Ctext%7BO%7D(l)

We use the following reaction enthalpy values:

%5CDelta%20H_f%5E%5Ccirc%20%5C%2C%20%5Ctext%7BCO%7D_2(g)%20%3D%20-393.5%20%5C%2C%20%5Ctext%7BkJ%2Fmol%7D%2C%20%5Cquad%20%5CDelta%20H_f%5E%5Ccirc%20%5C%2C%20%5Ctext%7BH%7D_2%5Ctext%7BO%7D(l)%20%3D%20-286%20%5C%2C%20%5Ctext%7BkJ%2Fmol%7D

The enthalpy of combustion of Cyclopropane is calculated as the sum of the products minus the reactants:

%5CDelta%20H_%7B%5Ctext%7Bcombustion%7D%7D%5E%5Ccirc%20%3D%20%5Cleft%5B%203%20%5Ctimes%20(-393.5)%20%2B%203%20%5Ctimes%20(-286)%20%5Cright%5D%20-%20%5Cleft%5B%20%5Ctext%7BCyclopropane%7D%20%2B%20%5Ctext%7BOxygen%7D%20%5Cright%5D

The enthalpy of formation of Cyclopropane is given as

%2B20.6%20%5C%2C%20%5Ctext%7BkJ%2Fmol%7D

, and the enthalpy of oxygen is zero since it is in its elemental form.

%5CDelta%20H_%7B%5Ctext%7Bcombustion%7D%7D%5E%5Ccirc%20%3D%20%5Cleft%5B%203%20%5Ctimes%20(-393.5)%20%2B%203%20%5Ctimes%20(-286)%20%5Cright%5D%20-%2020.6

%5CDelta%20H_%7B%5Ctext%7Bcombustion%7D%7D%5E%5Ccirc%20%3D%20%5Cleft%5B%20-1180.5%20%2B%20(-858)%20%5Cright%5D%20-%2020.6%20%3D%20-2038.5%20-%2020.6%20%3D%20-2059.1%20%5C%2C%20%5Ctext%7BkJ%2Fmol%7D

Thus, the standard enthalpy of combustion of Cyclopropane is approximately

-2092%20%5C%2C%20%5Ctext%7BkJ%2Fmol%7D

High-Yield Trend

Chapter Questions
1 MCQs

Official Solution

Enthalpy Change

High-Yield Trend

Chapter Questions 1 MCQs

Official Solution

Chapter Questions
1 MCQs