# Using the equation 2H_2 + O_2 -> 2H_2O, when 47g of oxygen are produced, how many grams of hydrogen must react?

Jul 2, 2016

5.9 g of hydrogen must react.

#### Explanation:

1. Write the balanced equation.

$2 \text{H"_2 + "O"_2 → "2H"_2"O}$

2. Calculate the moles of ${\text{O}}_{2}$.

${\text{Moles of O"_2 = 47 color(red)(cancel(color(black)("g O"_2))) × ("1 mol O"_2)/(32.00 color(red)(cancel(color(black)("g O"_2)))) = "1.47 mol O}}_{2}$

3. Calculate the moles of ${\text{H}}_{2}$.

${\text{Moles of H"_2 = 1.47 color(red)(cancel(color(black)("mol O"_2))) × ("2 mol H"_2)/(1 color(red)(cancel(color(black)("mol O"_2)))) = "2.94 mol H}}_{2}$

4. Calculate the mass of ${\text{H}}_{2}$.

${\text{Mass of H"_2 = 2.94 color(red)(cancel(color(black)("mol H"_2))) × ("2.016 g H"_2)/(1 color(red)(cancel(color(black)("mol H"_2)))) = "5.9 g H}}_{2}$