Chemistry converting to moles

Question

Calculate the total number of miles in the following mixture of elements: 54.0 g aluminum sulfide, 6.022x10^24 atoms gallium and 74.2 mL of nitrogen gas (assume at STP)

Answer 1

This is NOT a mixture of elements, as stated in the question, because aluminum sulfide (Al2S3) is a compound, not an element, and nitrogen gas (N2) is also not an element, but rather is a molecule. Having said that....

moles Al2S3 = 54.0 g x 150 g/mole = 0.360 moles

moles gallium = 6.022x1024 atoms x 1 mole/6.022x1023 atoms = 10.0 moles

moles N2 gas @ STP = 74.2 ml x 1 L/1000 ml x 1 mole/22.4 L = 0.00331 moles

Add them up to find total moles.

Total moles of atoms, molecules and compounds present = 10.4 moles