When calculating energy changes from bond energies, what is the first thing you should do?

1. Identify the Reaction

The first step in calculating energy changes from bond energies is to clearly identify the chemical reaction you are analyzing. Write the balanced equation for the reaction, including all reactants and products.

2. List the Bonds Broken and Formed

Next, determine which bonds are broken in the reactants and which bonds are formed in the products. This will guide you in calculating the total energy input and output.

3. Gather Bond Energy Values

Once you have identified the bonds involved, refer to a table of average bond energies to find the relevant values for each bond. This information is crucial for determining the energy changes associated with breaking and forming bonds.

4. Calculate Energy for Bonds Broken and Formed

You'll need to calculate the total energy required to break the bonds in the reactants and the total energy released when forming the bonds in the products. The formula is:

$\text{Energy change} = \text{(Total energy of bonds broken)} - \text{(Total energy of bonds formed)}$

5. Analyze the Results

Evaluate the calculated energy change to determine whether the reaction is exothermic or endothermic. If the value is negative, the reaction releases energy (exothermic), while a positive value indicates an energy-absorbing (endothermic) process.

By following these steps, you can effectively analyze energy changes related to bond energies in a given chemical reaction.