By using the bond enthalpies and bond energies in thermochemical equations to calculate the reaction enthalpy of; H + Br=2HBr

To calculate the reaction enthalpy of the reaction H + Br2 → 2HBr using bond enthalpies or bond energies, you need to follow these steps:

Step 1: Understand bond enthalpy and bond energy.
Bond enthalpy or bond energy is the amount of energy required to break one mole of a particular type of chemical bond in a gaseous substance. It is usually represented in kilojoules per mole (kJ/mol).

Step 2: Gather the bond enthalpy values.
To calculate the reaction enthalpy, you need the bond enthalpy values of the bonds involved in the reaction. The bond enthalpy values can be obtained from reliable sources such as textbooks or online databases.

In this case, you need the bond enthalpy values of the H-H bond, Br-Br bond, and H-Br bond.

Step 3: Calculate the energy required to break the bonds.
For the reaction H + Br2 → 2HBr, you need to break one H-H bond, one Br-Br bond, and form two H-Br bonds.

The energy required to break the bonds is calculated by multiplying the number of bonds by their respective bond enthalpy values. Since you have only one of each bond to break, you'll use their enthalpies directly.

Step 4: Calculate the energy released or absorbed when the new bonds are formed.
The energy released or absorbed when new bonds are formed is calculated by multiplying the number of new bonds formed by their respective bond enthalpy values. Since you form two H-Br bonds, you'll use the H-Br bond enthalpy value.

Step 5: Calculate the reaction enthalpy.
To calculate the reaction enthalpy, you need to subtract the energy required to break the bonds (bond energy of reactants) from the energy released or absorbed when the new bonds are formed (bond energy of products).

The reaction enthalpy (ΔH) can be calculated using the formula:
ΔH = Σ(bond energy of bonds broken) - Σ(bond energy of bonds formed)

In this case, it will be:
ΔH = [1 × (bond enthalpy of H-H) + 1 × (bond enthalpy of Br-Br)] - [2 × (bond enthalpy of H-Br)]

Step 6: Calculate the reaction enthalpy value.
Plug in the obtained bond enthalpy values and calculate ΔH.

It's important to note that the accuracy of the calculated reaction enthalpy depends on the accuracy of the bond enthalpy values used. Also, bond enthalpy values can vary depending on the specific compounds involved and the reaction conditions.