# Chemistry

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8.40 grams of Hydrogen gas reacts with 48.2 grams of Oxygen gas.
Give the mass of the water vapor produced and the mass of the excess reactant left over.

Can somebody please explain stoichiometry to me? I've failed the test and the retest. I'm usually able to balance the equation, but after that I get stuck. I just don't get it. :(

• Chemistry -

What you have posted is a limiting reagent problem. Basically, you solve those by solving TWO simple stoichiometry problems, identifying the limiting reagent (it produces the smaller amount of product), and go from there.
Here is a stoichiometry problem with all of the steps. Just follow the steps. Post back if there is something you don't understand.
http://www.jiskha.com/science/chemistry/stoichiometry.html

• Chemistry -

Umm, I don't understand, how do I found out what the limiting reagent is?

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