Ethane burns in air to form carbon dixode and water vapor.
2 H3C¬CH3( g) + 7 O2( g)¡4 CO2( g) + 6 H2O( g)
Use average bond energies to calculate ΔHrxn for the reaction.

Verified step by step guidance

1. Identify the bonds broken in the reactants: In ethane (C2H6), there are C-C and C-H bonds. In O2, there are O=O bonds.
2. Identify the bonds formed in the products: In CO2, there are C=O bonds. In H2O, there are O-H bonds.
3. Use the average bond energies to calculate the total energy required to break the bonds in the reactants. This involves multiplying the number of each type of bond by its bond energy and summing them up.
4. Use the average bond energies to calculate the total energy released when the bonds in the products are formed. Again, multiply the number of each type of bond by its bond energy and sum them up.
5. Calculate the enthalpy change (ΔH_rxn) for the reaction using the formula: ΔH_rxn = (Total energy of bonds broken) - (Total energy of bonds formed).

Key Concepts

Bond Energies

Bond energies refer to the amount of energy required to break a bond between two atoms in a molecule. In chemical reactions, the total energy required to break the bonds in the reactants is compared to the energy released when new bonds are formed in the products. This concept is crucial for calculating the enthalpy change (ΔHrxn) of a reaction, as it allows us to estimate the energy changes associated with bond breaking and forming.

Enthalpy Change (ΔHrxn)

The enthalpy change (ΔHrxn) of a reaction is the difference in energy between the products and the reactants, indicating whether a reaction is exothermic (releases heat) or endothermic (absorbs heat). It can be calculated using the formula ΔHrxn = Σ(Bond Energies of Reactants) - Σ(Bond Energies of Products). Understanding this concept is essential for predicting the energy dynamics of the combustion of ethane.

Combustion Reaction

A combustion reaction is a chemical reaction that typically involves a hydrocarbon reacting with oxygen to produce carbon dioxide and water, releasing energy in the form of heat and light. In the case of ethane, the balanced equation shows that it reacts with oxygen to produce carbon dioxide and water vapor. Recognizing the characteristics of combustion reactions is important for applying bond energy calculations to determine the overall energy change.