Which of the following has 1.2 times 10 (24) hydrogen atoms

Step 1: Find the mole ratio for each of the choices, and then multiply mole ratio by the 1 mole of H20 and Avogadro's number (6.022 x 10^23), so you will have this for each choice

1 mole H2O ( ratio /ratio) (6.022 x 10^23 / 1 mole) = atoms

One: 1 mole of water (H2O

You have 2 mole of H to 1 mole H2O, so the ratio is 2 to 1 or 2:1, and you have

1 mol H2O x (2 mol H / 1 mol H2O) x (6.022x10^23 atoms H / mol H) = 1.2 x 10^24

So, we can stop right here, because we have the value you were looking for.  If you want, you can work the other 3 in the same manner.

1 mol CH4 x (4 mol H / 1 mol CH4) x (6.022x10^23 atoms H / mol H) =

2 mol NH3 x (2 mol H / 1 mol NH3) x (6.022x10^23 atoms H / mol H) =

2 mol H2 x (2 mol H / 1 mol H2) x (6.022x10^23 atoms H / mol H) =

I tried as hard as i could then i noticed i answered this on my test and i got it right so i just typed it all in

1 mole of water (H2O)

Explanation:

2 hydrogen atoms so 2 x 1 mole (or 6.022 x 10^23 atoms) = 1.2 x 10^24 atoms

your answer would be a. 12.5 kg