Answer to Question #170234 in General Chemistry for Sam

Question

calculate the number of moles of oxygen required to to yield 72g of water

Answer 1

Mass of Water = 72 g

Molar mass of water(H₂O) = 18 g/mol

Moles of water produced = $\dfrac{72}{18}=4\space mol$

$H_2+\dfrac{1}{2}O_2\longrightarrow H_2O$

According to balanced chemical reaction,

1 mol H₂O is produced by the reaction of 1/2 mol O₂

4 mol H₂O is produced by the reaction of $4\times\dfrac{1}{2}=2\space mol$ O₂

Moles of O₂ required = 2 moles