5.2 grams of water undergo electrolysis, how many grams of oxygen gas is produced?

Question

I need to know how to set up the problem.

Answer 1

This is a stoichiometry problem

H₂O ----> H₂ + O₂

Start by balancing the equation.

2H₂O ----> 2H₂ + O₂

Then convert your 5.2 grams to moles

5.2 g H₂O X 1mole H₂O/18gH₂O = 0.289 moles (i used rounded values for the formula mass of H₂O)

Now that you know the number of moles use the molar ratio to find the number of moles of H₂ and O₂

0.289 Moles H₂O X 2 moles of H₂/2 moles of H₂O this yields 0.289 moles of H₂

_similarly

0.289 Moles H₂O X 1 moles of O₂/2 moles of H₂O this yields 0.145 moles of O₂

Now convert the moles of both H₂ and O₂ back to grams by using their formula masses

0.289 moles of H₂ X 2 gH₂/mole H₂ =0.578 g of H₂

similarly

0.289 moles of O₂ X 32 g O₂ /mole O₂ = 9.248 g of O₂