HELP!
Suppose 4.0 grams of H2 were used? How many grams of water would be produced?

36g

Explanation:

Given parameters:

Mass of H₂  = 4g

Unknown:

Mass of water produced  = ?

Solution:

The reactants in this experiment are hydrogen and oxygen gas. The product formed will be water, H₂O.

 Now write the reaction equation first;

                   2H₂  + O₂  →  2H₂O

Find the number of moles of Hydrogen gas;

         Number of moles  =  

  Molar mass of H₂  = 2(1) = 2g/mol

        Number of moles  =   = 2moles

From the balanced reaction equation;

             2 moles of H₂ will produce 2 moles of H₂O

So, mass of H₂O produced;

        Mass of H₂O = number of moles x molar mass

   Molar mass of H₂O  = 2(1) + 16  = 18g/mol

    Mass of H₂O  = 2 x 18 = 36g