How many moles of oxygen would
be consumed to produce 68.1 g
water?

4.75 moles of oxygen would be consumed by water

Explanation:

Given data:

Mass of water produced = 68.1 g

Number of moles of oxygen consumed = ?

Solution:

Chemical equation:

C₃H₈ + 5O₂      →    3CO₂ + 4H₂O

Number of moles of water:

Number of moles = mass/molar mass

Number of moles = 68.1 g/ 18 g/mol

Number of moles = 3.8 mol

Now we will compare the moles of water with oxygen.

                H₂O         :            O₂

                  4            :              5

                 3.8          :           5/4×3.8 = 4.75 mol