## Tuesday, February 22, 2011

### Enthalpy Calculations...*sigh*

Sooooooooo, did you ever think we were done with the mole?
DON'TTHINK THAT WAY because I'm about to prove you wrong.
Enthalpy calculations=the usage of MOLES -insert dramatic scream-
And the return of the mole also means the return of sig figs, btdubs. -insert double dramatic scream-

That my friends was a double double, double double combo. (:

Let's get started:
ΔH--> change in energy of a reaction; expressed in kJ/mol

Here is an example:
C10H8+12O2-->10CO2+4H20+436kJ
Hence, ΔH=

1)      -436kJ
1 mol C10H8

2)   -436kJ
12 mol O2

3)    -436kJ
10 mol CO2

4)    -436kJ
4 mol H2O

Once you've identified these, it will be easy to do conversions.

eg. Calculate how many grams of O2 would be needed to produce 1500kJ of energy.

-1500kJ x 12 mol O232g    = 1321.1 kJ
-436kJ         1 mol

**SIG FIGS!!**   So, the answer is 1300 kJ.

Watch this video if you're still confused!!

GOOD LUCK WITH THIS CONFUSING SECTION!! :D

Written by Jialynn.