Answer:
First, the number of ammonium sulfide molecules should be calculated:
N = NA × n,
where NA - the Avogadro number, n - number of moles.
N (ammonium sulfide) = 6.022 × 1023 × 8.5 mol = 51.187 × 1023.
The moelcular formula of ammonium sulfide is (NH4)2S. It means that each molecule contains 8 hydrogen atoms.
As a result, 8.5 mol of (NH4)2S contain:
51.187 × 1023 × 8 = 41 × 1024 hydrogen atoms.
Answer: 41 × 1024 hydrogen atoms