Stoichiometry

Stoichiometry is the measurement and study of the relationships and quantities between products and reactants.

Let's examine a chemical equation:

__C4H10(g) + __ O2(g) ---------> __CO2(g) + __H2O(l)
First we must balance it!

2 C4H10 + 13 O2(g) -------> 8 CO2(g) + 10 H2O(l)
The numbers in front of the products and the reactants are called mole ratios.
We use this in stoichiometry to convert between grams and moles of the products and reactants.

Example:

If 24.0 grams of C4H10 was reacted with O2, how many grams of CO2 would be formed??

Make a mole map!!!!

You cannot convert directly from grams of C4H10 to grams of CO2 so first you must convert to moles.

Here is how you set up your equation:

24.0 g C4H10 x 1 mole/molar mass C4H10- This converts grams of C4H10 into moles.
Now you use stoichiometry to determine moles of the CO2

Remember: What you want/what you have

So: multiply moles of C4H10 by 8 mol CO2/ 2 mol C4H10
Now you have moles of CO2. All thats left is to convert moles of CO2 into grams of CO2

Multiply moles of CO2 by the molar mass of CO2/1 mole.

Your answer will be: 72.8 g CO2

Ex. 2

2 KClO3(s) -------> 2KCl(s) + 3O2(g)

How many molecules of KCl will be formed when 45.0 g KClO3 is decomposed?

45.0 g KClO3 x 1mole/122.6 x 2 KCl/2 KClO3 x 6.022 x 10^23/1 mole=2.21 x 10^23 molecules of KCl

http://www.youtube.com/watch?v=nf8J2g_A8uE
Here is some extra help!