Thermochemical Equations
Project: Modeling Energy Changes
In this assignment, you will write and balance a chemical equation. Then, you will use a table of enthalpy
values to calculate the energy change in the reaction. Next, you will create a model of the energy change
in the reaction. Finally, you will write an explanation that describes the energy change in the reaction.
Step 1: Write and Balance the Chemical Equation
For this project, I will focus on the reaction of hydrogen gas (H2) combining with oxygen gas (O2) to form water (H2O).
The balanced chemical equation for this reaction is:
2H2(g) + O2(g) → 2H2O(l)
Step 2: Calculate the Energy Change
To calculate the energy change in the reaction, we will use the following enthalpy values:
ΔHf° for H2(g) = 0 kJ/mol
ΔHf° for O2(g) = 0 kJ/mol
ΔHf° for H2O(l) = -286 kJ/mol
The total energy change for the reaction can be calculated using the equation:
ΔH = ΣΔHf(products) - ΣΔHf(reactants)
ΔH = 2(-286 kJ/mol) - [2(0 kJ/mol) + 0 kJ/mol]
ΔH = -572 kJ/mol
Step 3: Create a Model of the Energy Change
To visually represent the energy change in the reaction, I will create a graph showing the energy levels of the reactants, products, and the energy change (ΔH) of the reaction.
Step 4: Write an Explanation
The negative value of -572 kJ/mol indicates that the reaction is exothermic, meaning it releases energy in the form of heat. In this reaction, the bonds between hydrogen and oxygen atoms in water are stronger than the bonds in the reactants, leading to a net release of energy. The model visually shows that the energy of the products is lower than that of the reactants, illustrating the energy change in the reaction. Overall, this reaction is energetically favorable as it releases heat energy.