Wait, wait, wait.....stoichio wha?????????
The Greek root stoichio means element, and mentry meaning measurement.
So, it's all about element measurements. At least, that's what the word means.
What it is really about is the analysis of chemical reactions, measuring amounts of elements and compounds that are involved in any given reaction. It is the relationship of reactants used vs products created.
E.g. 2H2 + O2 ---> 2H2O From our previous knowledge, we can say:
2 g/mol 32 g/mol 18 g/mol
4 H's 2 O 4 H's 2 O's
From the same example, we can take the coefficients as a number of moles or a number of molecules. So in other words, we can treat them as:
2 moles H2 + 1 moles O2 ---> 2 moles H2O
The ratio we are given, 2:1:2 is called the mole ratio.
In order to perform the stoichiometry calculations, we must have:
A balanced chemical reaction
A ratio of molecules or moles of substances in the chemical reaction (you will get this when the equation is balanced)
The coefficients tells us how many moles of each substance were reacted or produced. This is where the deadly mole conversion factors come back into play!
Let's start with an example:
How about: Na + Cl2 ---> NaCl
So first, let's check if it's balanced.
2Na + Cl2 ---> 2NaCl
Now it is! Ok, so how many moles of NaCl are produced when 12 moles of Na are produced?
We start off writing down 12 moles Na. To get to moles of NaCl, we must multiply by where we want to go over where we started.
In other words: 12 moles Na X 2 mole NaCl
2 mole Na
(There are 2 moles of Na for every 2 moles of NaCl, as shown in the chemical equation.)
We can cancel out moles of Na to get to our answer. Through simple multiplication, we realize that 12 moles of NaCl are created when 12 moles of Na reacts with chlorine.
Now enough of us, and time for you to get cracking!
http://www.sciencebugz.com/chemistry/chprbstoich.html
http://www.standnes.no/chemix/examples/stoichiometry-problems-chemistry.htm
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