Endothermic and Exothermic Reactions!

-All chemical reactions involve changes in energy or heat

-Exothermic reactions release energy
-Endothermic reactions absorb energy


Using energy graphs, we will be able to see whether the reaction is endothermic or exothermic.

 -energy is represented in the form KJ

-The flat part of the graph before the bump  labelled "reactants" represents the energy of the reactants. This is how much energy the compounds START with.

-The flat part of the graph after the bump labeled "Product" represents the energy of the products. This is how much energy the compounds END with.

-The energy of activated complex,, is the potential energy of the transition state between the reactants and the products. 

-it's the highest possible amount of energy the compounds can reach in the reaction process

-The activation energy is the energy that is added to to the reactants to get them to progress. 

-Delta H or the change in enthalpy (heat contained in the system) during the reaction. This is found by subtracting the energy of the reactants from the energy of the products.
     -A negative H will signify an exothermic reaction - you end up with less energy than you started with
     -A positive H will signify an endothermic reaction - you end up with more energy than you started with

Once you find the H, you can use it in equations like this:

4Na + O2= 2Na2O + 520KJ

If the energy was written on the right side, it meant that the reaction is exothermic, therefore there is less energy in the products

If energy is written on left side, it meant that the reaction is endothermic.

This site might be very helpful!

http://www.saskschools.ca/curr_content/chem30_05/2_kinetics/practice/q3_2.htm