Calculating moles and mass?

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.

Calculating moles and mass?
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)
Reply:Moles of H2 = 1.89*2/18





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





Just subtract for the rest.