Calculating moles and mass?

Question

1Calculate the number of moles in 58.2 g of Se. SIG. FIG.

2Calculate the number of moles in 1.43x1022 NO2 molecules. SIG. FIG.

3Calculate the mass (in g) of 6.16 moles of H2O. SIG. FIG.

4Calculate the number of moles in 86.2 g SO3. SIG. FIG.

5Calculate the number of oxygen atoms in 20.6 g SO3. SIG. FIG.

I normally wouldn’t ask someone to do hw for me but right now I have no other choice since I need the time to study math If you help me fine ill give you five stars.

Answer 1

number of avogadro is Na=6.02 * 10^23

moles= mass/MW
once you have the moles the number of atoms are
n. atoms = Na * moles

MW are easily calculable if you have a periodic table of the elements.
if not go here:
http://www.webelements.com

in total, you can finish this exercise in less than 2 minutes. Probably it took more to you to recheck what you have written in order to give data without mistakes. (so that we could solve your hw correctly)

Answer 2

Moles of H2 = 1.89*2/18

Moles of N2 = 2.18*0.235/(28*1.23)

Just subtract for the rest.