Given this equation;

2H2 + O2 = 2H20

answer the following;

a) If you start with 10.0g of H2, how many mol of H20 is produced?
Why do I get the answe of 5 moles? I know the answer is 4.95moles. I can't figure it out.

The atomic mass of hydrogen is 1.0079, not 1. Using this you get an answer of 4.96 moles.

Thank you for posting your question to the Ask Me Help Desk.

As a chemistry teacher myself, I have all of my students round atomic masses to two decimal places. Then there is some consistency in the answers that my students get.

For the case of hydrogen this means we would use 1.01g and for H2 we would use 2.02g.

After going through the calculations, I then get 4.95 mol H2O.