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?

Answer 1

To produce a molar conversion, you need to know the molar mass of each molecule. I presume you mean there are 192 grams of O2. The molecular weight of oxygen is 16 g/mol. Therefore, O2 is 32 g/mole.

If there are 192 grams of O2, then:
192 grams x (1 mole/32g) = 6 moles of O2.

To react each mole of oxygen, you need 2 moles of hydrogen (H2). You can see this in the equation 2H2 + O2 --> 2 H20.
To react 6 moles of O2, you need 12 moles of H2.
Now that we have the total moles of hydrogen needed, we now use the molar mass of H2 (2 grams/mole)
12 moles H2 x (2 grams/1 mol H2) = 24 grams of H2.