Re: How much hydrogen and oxygen gas does a gallon of water contain? Thanks.

How much?  What units are you interested in?  I mean the easiest answer... 
and the one that belongs on "Ask Dr. Science" not Mad Scientist is 'a 
gallon.'  But that's not what they gave me this question for.  
First of all.  Lets assume some parameters. If the water is at its standard 
temperature it has a density of 1 gram per 1 millilter or cubic 
centimeter... or 1 kilogram per 1 liter.  

1 liter = 1.06 quarts
4 quarts = 1 gallon
so 1 gallon = 3.77 liters or 3.77 kg
1 mole of water is 18 grams so you have 209 moles of water.  Each water has 
1 oxygen and 2 hydrogen.  So for oxygen you have 209 moles of oxygen or 3350 
grams (3.35 kg).  For hydrongen you have 418 moles of hydrogen or 418 grams 
(.418 kg).  

If you want that in pounds... 1 kg =  2.2 lbs
so 7.37 lbs oxygen and .920 lbs hydrogen.  I'll let you multiply by 16 
yourself if you need that in ounces.

Hope that answers your question.

Greta Hardin