I find difficulty in solving this question: How many atoms of H & S are contained in 0.40 mole of H2S?

H₂S ? 2H + S

 1 mole H2S  contains = 2 moles of H or 2 X 6.023 x 10 ²³ atoms .

 .4 mol contains = .4 x 2 x 6.023 x 10 ²³ atoms.

Similarly, 1 mole H2S contains = 1 mole of S = 6.023 X 10 ²³

              .4 mol H2S contains = .4 x 6.023 x 10 ²³atoms