Ow many sulfur atoms are in 1.10 mol of aluminum sulfide?

Aluminum sulfide is Al₂S₃, which shows that there are 3 sulfur atoms per formula unit.

In one mole there is Avogadro’s number of atoms and Avogadro’s number = 6.02 x 10²³

In 1.10 mole = 1.10 x 6.02x10²³ = 6.62 x 10²³ formula units

Now multiply with 3 to get number of sulfur atoms present in 1.10 mol of Aluminum sulfide;

3 x 6.62x10²³ = 1.99 x 10²⁴

So, the answer is 1.99 x 10²⁴ sulfur atoms.

i believe you are right for all except the 3rd ( look at sqdancefan his answer is much better)