Re: Can you please give and explain the chemical formulas used in each step of

This is a big question.  For a thorough understanding of the process, try 
consulting a homebrewing book...the Joy of Homebrewing by Charlie Papazian 
is a good one.

Overall, several steps make up beer production.  Grains which contain 
starches are used to produce sugars, which are then acted upon by yeasts 
to generate alcohol, carbon dioxide and water.  Various flavors including 
hops are added.  Final carbonation occurs either by forcing carbon dioxide 
into the beer (what happens to most of the beers that you buy in the 
store) or by addition of a little sugar to the bottle just before bottling 
(called "bottle conditioned beers") which is further acted upon by the 
yeast to yield carbonation.

The grains contains starches, which the yeast is unable to act upon.  The 
grains also contain enzymes, which are species which can convert the 
starches to sugars.  You have enzymes in your saliva, for example.  These 
enzymes in the grains become activated when they are warmed.  Hence, the 
grains are soaked in warm water to generate sugars ("food" for the 
yeasts).  Flavors include hops (a bitter herb) and roasted grains.

I hope this helps. 
Please email me if you have further questions: weibelm@battelle.org

Best Regards,
Mike