How many hydrogen atoms are in 2.80 mol of ammonium sulfide?

You can see each (NH4) 2S has

2 N atoms

8 H atoms

1 S atom

So moles H atoms = 8 x moles (NH4) 2S

= 52.0 moles H

1 mole anything = 6.022x10^23 units of that anything

So number H atoms = moles H atoms x 6.022x10^23 atoms/mol

= 52.0 x 6.022x10^23 atoms/mol

= 3.13x10^25 atoms of H