What is the mass of 9 * 10 ^ 23 molecules of hydrogen sulfide H2S?

Given:
N (H2S) = 9 * 10 ^ 23

To find:
m (H2S) -?

1) Calculate the amount of substance H2S:
n (H2S) = N (H2S) / NA = 9 * 10 ^ 23 / 6.02 * 10 ^ 23 = 1.495 mol;
2) Calculate the molar mass of H2S:
M (H2S) = Mr (H2S) = Ar (H) * N (H) + Ar (S) * N (S) = 1 * 2 + 32 * 1 = 34 g / mol;
3) Calculate the mass of H2S:
m (H2S) = n (H2S) * M (H2S) = 1.495 * 34 = 50.83 g.

Answer: The mass of H2S is 50.83 g.