Determine the number of moles of H in 4.70mol H2O. Please help I tried different ways to do it and I got them all wrong.

Answer 1

You won't have trouble with this if you just look at the formula.
You have 4.70 mol H2O
There are two H atoms in 1 molecule H2O.
Therefore, there must be 2*4.70 = 9.40 mols H in 4.70 mols H2O.
How many mols O in 4.70 mols H2O? That's 4.70 mols, of course.

Said another way, you have 2 mols H for every 1 mol H2O and 1 mol O for every 1 mol H2O.
So for 50 mols H2O you have 100 mols H and 50 mol O.