The molar mass of H2O is 18.01 g/mol. The molar mass of O2 is 32.00 g/mol. What mass of H2O, ins grams, must react to produce 50.00 g of O2

56.28 g

Explanation:

First change the grams of oxygen to moles.

(50.00 g)/(32.00 g/mol) = 1.5625 mol O₂

You have to use stoichiometry for the next part.  Looking at the equation, you can see that for every 2 moles of H₂O, 1 mole of O₂ is produced.  Convert from moles of O₂ to moles of H₂O using this relation.

(1.5625 mol O₂) × (2 mol H₂O/1 mol O₂) = 3.125 mol H₂O

Now convert moles of H₂O to grams.

(3.125 mol) × (18.01 g/mol) = 56.28125 g

Convert to significant figures.

56.28125 ≈ 56.28