Calculate the Energy, We Must!

CALCULATING ENERGY 101

        What an honour to have Master Jedi, Yoda, teach us about calculating energy in endothermic and exothermic reactions. With his great wisdom and knowledge, lets " pitter patter lets get at her."

Young Padawans of PinchOfKCN, If you may not have noticed, absorbing(consumption) or release of energy can be found right in the endothermic/exothermic reaction. In exothermic reactions, energy is usually on the right side of the equation and has negative  ΔH. For endothermic reactions, energy is found on the left hand side and has positive  ΔH.

Young ones be CAREFUL, It's the "Return of The Moles", they bring back horrid memories and cookies...
 ΔH is usually expressed as kJ per moles of one of the chemicals in the equation. Basically it should look like this

-812kJ

1mol CH4

Eg.

CH4 + 2O2 --> CO2 + 2H20 + 812kJ 

Question: How many beauty marks(moles) of CH4 is needed to produce 2100kJ of energy?

Step. 1 - Choose an element, then write the equation.

-2100kJ(negative because energy is needed) x 1mol of CH4

                                                                           812kJ

And you should get your answer 2.6mol CH4

Just for the trainees, How many grams of CH4 is needed to produce 2100kJ of energy?

Take the answer from the question above and convert it to grams! 2.6mol x 16 grams

                                                                                                                      1mol 

You should get 41.6 grams of CH4 is needed to produce 2100kJ of energy.

You are all ready to become a Jedi after watching this video!

Master Yoda has 1 last thing to say...