Wednesday, February 23, 2011

Let it be, and learn enthalpy!!!!!!

Oh hello there, it is so nice to see you : )

Guess what we're learning about today? Starts with enthalpy...YESS ENTHALPY (Mr. Hogaboam joke)

Now, in order to actually succeed in learning this foreign topic, I must tell you what enthalpy actually MEANS. Enthalpy, H, is the HEAT contained in a system.

ΔH = the change in enthalpy during a reaction a.k.a kJ/mol

The equation for the total change in enthalpy is:
ΔH = HProduct - HReactant
             HReactant = the heat energy contained in the reactant
          HProduct = the heat energy contained in the product

Now I bet you guys are just dying and so gosh darn excited to move on that you'd fly off a bridge. Well this is your lucky day!

Let us move on to exothermic and endothermic reactions shall we?
An EXOTHERMIC reaction GIVES OFF heat to its surroundings
A trick to remember this is: Heat EXits from the reactants

An ENDOTHERMICreaction ABSORBS heat from its surroundings
A trick to remember this is: Heat ENters the reaction


Energy of the activated complex = potential energy of the "transition state" between reactants and products
Activation Energy (Ea) = the energy that must be added to get the reaction to rpogress (reactants to activated complex)

Lets start with some example equations!!! : D
******Remember, when Kj is on the left side of the equation, it is endothermic and positive. When kJ is on the right side of the equation, it is exothermic and negative*****

Ex/ For the following reaction, calculate the energy released when 1.56 moles of H2O is produced?
CH4 + 2 O2 ----> CO2 + 2 H2O + 918kJ

1.56 mol H2O x   -918 kJ    = 716.04 kJ energy released = 716 kJ or -716kJ
                           2 mol  H2O

Ex/ Using CH4 + 2 O2 ----> CO2 + 2 H2O + 918kJ again, how many grams of CO2 would be needed to produce 2300 kJ of energy?

-2300 kJ x 1 mol CO2  x 44.0g CO2  = 110.2396514g CO2 = 110g CO2
                          - 918 kJ        1 mol CO2

If you still don't understand after my BEAUTIFUL explanatin, you can go to this video to learn what I just said again : )

Lastly, I'll just put in a not so funny joke and hopefully you'll get it : )
This was sent in to us by Robert L. LaDuca (well not really I just found it)

"Yesterday when talking about energy units/enthalpy I drew a man, woman, and child on the board. I put a "J" on each of them. Then I kept on going,without paying it any attention. I let them figure it out, a minute or so later got groans and laughter. Yup, the "Family Joule". ;)"

haw haw haw haw haw haw. Yea this is only funny if you've watched the show "Family Jewels" starring Gene Simmons and his family (wife Shannon Tweed and their kids Nick and Sophie). OHH NOW YOU GET IT? ;)

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