CH4 + 202 → CO2 + 2H2O
How many grams of O2 needed to produce 36 grams of H2O?

Mass = 64 g

Explanation:

Given data:

Mass of water produced = 36 g

Mass of oxygen needed = ?

Solution:

Chemical equation:

CH₄ + 2O₂       CO₂ + 2H₂O

Number of moles of water produced:

Number of moles = mass/molar mass

Number of moles = 36 g/ 18 g/mol

Number of moles = 2 mol

Now we will compare the moles of water and oxygen.

             H₂O       :          O₂

                2         :           2

Mass of oxygen:

Mass = number of moles × molar mass

Mass =  2 mol × 32 g/mol

Mass = 64 g

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