Question

using the equation 2h2+o2-->2h2o if 192g of oxygen are produced how many grmas of hydrogen must react with it

Answer 1

Equation: 2H₂ + O₂ → 2H₂O

Now, Given mass of Oxygen = 192 g
Molar mass of Oxygen = 16 g/mol

No. of moles in Oxygen = 16/192 = 0.0833

Now, for every mole of Oxygen, 2 mole of Hydrogen will form, 
so, Number of moles of Hydrogen = 0.0833 * 2 = 0.167

Given mass = Number of Moles * Molar mass
Given mass = 0.167 * 2
m = 0.33 g

In short, Your Answer would be: 0.33 g

Hope this helps!

Answer 2

Mol H2O = weight H2O / MW H2O = 1.8 / 18 = 0.1 mol
Weight H2 = mol H2 x MW H2
1 Mol H2 --> 1 mol H2O
So :
Weight H2 = mol H2O x MW H2 = 0.1 x 2 = 0.2 grams