Question

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

Answer 1

Mass of H2O = 56.27 g

Step-by-step explanation:

Given:

Molar mass of H2O = 18.00 g/mol

Molar mass of O2 = 32.00 g/mol

Mass of O2 produced = 50.00 g

To determine:

Mass of H2O reacted

Step-by-step explanation:

Water breaks apart during electrolysis to produce O2 and H2. This can be represented as:

`2H2O \rightarrow 2H2 + O2`

Moles of O2 produced =
`(Mass\ of\ O2)/(Molar\ Mass) = (50.00)/(32.00) = 1.563`

Based on the reaction stoichiometry:

2 moles of H2O produces 1 mole of O2

Therefore, moles of H2O that would react to produce 1.563 moles of O2 is:

=
`(1.563\ moles\ O2*2\ moles\ H2O)/(1\ mole\ O2) =3.126 moles`

`Mass of H2O = Moles of H2O * Molar mass \\= 3.126 moles * 18 g/mol = 56.27 \ g`

Answer 2

This reaction is called the electrolysis of water. The balanced reaction is:
2H2O = 2H2 + O2
We are given the amount of O2 produced from the electrolysis reaction. This will be the starting point of our calculation.

50.00 grams O2 ( 1 mol O2 / 32 grams O2) ( 2 mol H2O / 1 mol O2) ( 18.01 g H2O / 1 mol H2O ) = 56.28 g H2O