Question

Calculate the approximate enthalpy change, ?Hrxn, for the combustion of one mole of methane a shown in the balanced chemical equation: CH4+2O2?2H2O+CO2 Use the values you calculated in Parts A, B, C, and D, keeping in mind the stoichiometric coefficients.

delta H CH4=1656 kJ/mol

delta H O2=498 kJ/mol

delta H H2O=-928 kJ/mol

delta H CO2=-1598 kJ/mol

Answer 1

Concepts and reason

Combustion reactions:

The chemical reaction in which an organic compound or hydrocarbon (H and C) burns with oxygen and forms water and carbon dioxide is represented as combustion reaction. The combustion reaction is exothermic reaction in which heat releases in the form of energy.

Bond enthalpy:

Bond enthalpy is one of the thermodynamic quantities that measures the bond strength in the molecules (energy stored in the form of chemical bond). It is defined as the amount of energy that is needed for breaking the chemical bonds in the molecules. It is also known as average bond energy or bond dissociation enthalpy. It is usually expressed in.

Fundamentals

The arbitrary reaction is given below:

Here

and are the reactants.

is the product.

The approximate enthalpy change for the gas phase reaction can be estimated by the following formula:

Here

indicates the bond dissociation energy of reactants

indicates the bond dissociation energy of products.

represents the bond dissociation energy.

In the above formula, n and m are the coefficients of reactants and products, respectively.

Stoichiometric coefficients:

A stoichiometric coefficient is a simple whole number that is used to determine the relative number of moles or molecules in a balanced chemical equation.

The given combustion reaction of methane is as follows:

In the above reaction, methane burns with oxygen to form carbon dioxide and water as products.

The given balanced chemical equation is as follows:

Use the following equation to calculate the change in enthalpy for the given combustion reaction of one mole of methane.

Substitute the values of the substances.

Ans:

Hence, the approximate enthalpy change,, for the combustion of one mole of methane is .