Mass to Mole Stoichiometry?

1. How many moles of oxygen are produced by the decomposition of 15.0 grams of potassium chlorate?

2. How many moles of hydrogen are produced from the reaction of three grams of zinc with an excess of hydrolic acid?

3. How many moles of oxygen are necessary to react completely with four grams propane (C3H8) ?

4. How many moles of potassium nitrate are produced when two grams of potassium phosphate react with two moles of aluminum nitrate?

If you can help me out with this and my other questions that'd be great!

And.. if you could show how to do it i'd also appreciate that.

I honestly dont get any of this and the teacher isnt helping me any to try and pass the semester he wont even let me do extra credit!

So yea.. if you could teach me in some way THANKS!!

All of these require these "Stoich Steps":

1st -- Write a balanced equaation

2nd -- Identify the "known" and "unknown" -- put them on the outside edges of a conversion factor series

3rd -- Put the mole ratio between the unknown and known thing in the middle of the problem

4th -- If needed, use the molar mass (add 'em UP!) to convert grams to moles or moles to grams

Let's look at the first problem:

Decomposition of potassium chlorate

You must know the products of the decomposition of a metal chlorate: metal chloride plus oxygen.