2h2+o2 —-> 2h2o when 18g of water are produced, how many grams of hydrogen must react

Mass of hydrogen =  2 g

Explanation:

Given data:

Mass of water = 18 g

Mass of hydrogen react = ?

Solution:

First of all we will write the balance chemical equation,

2H₂ + O₂   →  2H₂O

Number of moles of water = mass / molar mass

Number of moles of water =  18 g/ 18 g/mol

Number of moles of water =  1 mol

Now we compare the moles of water and hydrogen from balance chemical equation.

                           H₂           :           H₂O              

                            2            :               2

                            1             :               1

Mass of hydrogen = number of moles / molar mass

Mass of hydrogen = 1 mol × 2 g/mol

Mass of hydrogen =  2 g