Answer:
Balance the equation first
[tex]2H_{2} \ + \ O_{2} \ --> \ 2H_{2}O[/tex]
6.58g of Oxygen gas
Divide 6.58g by molar mass of oxygen (32g/mol)
6.58/32 = 0.205625 mol
Use mol to mol ratio from looking at the coefficients of the reactants, the mol ratio of Hydrogen gas to Oxygen gas is 2:1, so for every 1 mol of Oxygen, you need 2 times the mol of hydrogen for it to make water.
0.205625 * 2 = 0.41125 mol
To get the mass of hydrogen gas needed in the reaction, turn 0.41125 mol into mass by multiplying it with Hydrogen gas's molar mass, which is 2.02 g/mol.
0.41125 * 2.02 ≈ 0.83g of H2
