Chemistry
posted by Ryan on .
I have no idea how to work this problem can anyone help explain this to me?
2H2O=2H2+O2
if 30mL of hydrogen are produced in the reaction above, how many militers of oxygen are produced?

Look at the equation. That's what they are for. The coefficients in the equation tell you that you have 2 mols hydrogen for every 1 mol oxygen. So 2 and 1, 4 and 2, 6 and 3, 8 and 4, 10 and 5 etc. Get the idea?

Do I have to change the milliters into liters? That is where I get confused.

Not unless you want to do so. Here is the way the units work.
30 mL H2 x (1 mol O2/2 mols H2) = ?? mL O2. Notice that you start with 30 mL H2 in the numerator. H2 in the numerator cancels with H2 in the denominator of the second term. mols cancel top and bottom. That leaves mL O2 for the answer and that's what the problem asked for. You COULD change to liters, the answer will come out in liters, then changre back to mL but that's a lot of extra work; especially when the problem asks for mL. 
thank you, DrBob, now I understand.