Rates of Reaction
What are Bond Energy Calculations.
You can calculate the overall change in energy for a
reaction by using the values for the individual bond energies.
hydrogen + chlorine hydrogen chloride .
H 2 (g) + Cl 2 (g) 2 HCl (g)
The reactants are hydrogen and chlorine .
The product is hydrogen chloride.
You must put energy in to break the bonds in the reactants
before energy is given out by forming new bonds in the products .
The minimum amount of energy you need to put in
to make the reaction happen is called the activation energy.
When the bonds between the hydrogen and the
chlorine molecules (the reactants ) have been broken ,
then both hydrogen and chlorine exist as atoms.
When an atom of hydrogen and chlorine react
with each other they make a new bond ,
give energy out. and form the product hydrogen chloride.
What is the Bond Energy.
The bond energy is the amount of energy which
1) you must put in to break the bond ,
2) is given out when the new bond is formed.
The table below shows some bond energies which are
given in kilojoules ( thousand joules ) per mole of bonds.