1. The problem statement, all variables and given/known data If 100 g H2O contains 11.2 g H, what mass of water could be obtained from 3.06 g H2(g) reacting with an excess of O2(g)? 2. Relevant equations Mass % of X in a sample= (Mass of X in sample/ Mass of the sample)*100 3. The attempt at a solution The parts that confused me were 11.2g of H and the 3.06g H2. Why aren't both be H2 or H? Can anyone help me with this problem? THank you in advance. This is my effort: I look for the mass fraction of H in 100g of H2O: 11.2g of H/100g H2O= .112 Then, I find the Mass of H2O 3.06g/.112 = 27.3g H2O Is this correct?