[th3plan]

Hey guys i started reviewing chemistry and im getting confused on this problem. 

How many grams of aluminum will be completely oxidized by 44.8 L of oxygen?

I Saw how they worked out the problem and they had 2H(subscript 2 )O---> 2H(subscript 2) + O(subscript 2) .  Where in the world are they getting the 2 from ?  this throws me offf completely !  Any help would be great thanks

[Mitch]

Which 2 and why is there Hydrogen in your equation if you were talking about Aluminum & Oxygen?

[sdekivit]

in any case: if you know the conditions, you can calculate the amount of mol O₂ by using the molar volume of a gas. At t = 298 K and p = p₀ 1 mol of any gas will occupy a volume of 24.5 L.

otherwise you may use the gas law: (pV)/T = constant.

[lrn24gve]

The balanced equation is 2H2O --> 2H2 + O2.

The equation needs to have the same amount of hydrogen and oxygen on the same side. When you're breaking up H2O, you'll get hydrogen gas and oxygen gas. Both hydrogen and oxygen are diatomic, meaning they're found in compounds and not in their elemental state. Therefore, when you break up H2O to H2 and O, and you know that oxygen is diatomic, oxygen has to be O2. However, due to two oxygen atoms on the right side of the equation, the equation isn't balanced anymore. In order to balance the equation, you need to have two oxygens on the left side of as well so you hadd a 2 in front of the H2O. However, that leads to 4 hydrogen molecules on the left side. In order to balance that out, you add another 2 in front of the H2 to get it balanced.

I think you already know what I'm talking about but I wasn't sure which 2 you're confused on. Just in case, I gave a full explanation about balancing the equation. I hope I answered your question.