Using the equation 2H2 + O2 -- 2 H2O, if 192 g of O are produced, how many grams of hydrogen must react with it? Help me understand how to do this?

Question

Using the equation 2H2 + O2 --> 2 H2O, if 192 g of O are produced, how many grams of hydrogen must react with it? Help me understand how to do this?

thomaster · Answer

$\LARGE 2H_2+O_2\to2H_2O$

2 moles hydrogen gas reacts with 1 mol oxygen gas to produce 2 moles of water

The first thing I notice is that there's something wrong with the question. You know that 192 grams of O are produced. But O is not the product of this reaction right? 

Shouldn't it be 192 grams of $\LARGE H_2O$ ?

thomaster · Answer

or is it 192 g of O is used in the used in the reaction?

anonymous · Answer

No my question said if 192 g of oxygen are produced, how many grams of hydrogen must react with it?

anonymous · Answer

its stoichiometry, mass/mass and % yield

thomaster · Answer

Ah well seemed odd, but it's very simple.
You start with calculating the amount of moles $O_2$ you have.
1 mol $O_2$ is 32.998 grams (because the molecular weight of O is 15.999, you can check this on a periodic tabel)

Now you convert 192 gram to mole by simply dividing the 192 grams by the weight of 1 mol. so 192/31.998

anonymous · Answer

And that's the answer? Wow I had no clue it was this simple. my teacher described it totally different.

anonymous · Answer

I get 6 but my answers are 36, 12, 48, and 24

thomaster · Answer

Yea that's not the answer yet, the site crashed and wouldn't reload, sorry for that.

You know you have 6 moles of $O_2$
now you need to know how many moles of $O_2$ react with $H_2$
I kinda already gave the answer to that in my first reply.

anonymous · Answer

1mole of O2 reacts with 2 moles of H2?

anonymous · Answer

Hey im sorry I couldn't get on for some reason. 1 mole of O2 will react with 2 moles of h2 right?

jfraser · Answer

the whole wording of the question is incorrect. You can't produce $O_2$ because it is a $reactant$. You can $use$ $O_2$, and produce water, but the general principle is still balanced reactions produce useful ratios

anonymous · Answer

Im sorry, that's just what my paper said. I struggle with finding stuff like this. I can do the math, but I have a hard time figuring out what to use in the math

thomaster · Answer

Sorry the site wasn't working anymore yesterday.
1 mole of O2 reacts with 2 moles of H2 in this reaction, that's correct.
According to this ratio, 6 moles of O2 will react with 6*2=12 moles of H2.
So the last thing you have to do is calculate the amount of grams H2 which equals 12 moles. For hydrogen this is very simple as 1 mole H roughtly weighs 1 gram. So 1 mole H2 will weigh 2 gram. We have 12 moles so that'd equal 24 grams of hydrogen gas.