Determine the number of atoms in 2.25 moles of nitrogen gas.

I'm confused >.< Do I:

 

1) multiply 2.25 mol by 6.02 x 10^23 atoms or

or

2) multiply 2.25 mol x 6.02 x 10^23 molcules x 2 atoms.

or is it something else?

 

Also, how do I do this problem?

Calculate the mass of 3.01 x 10^23 formula units (ions) of Strontium hydroxide.

 

Please help if you can. ~____~

It's number 2. One mole of something is avogadro's number of molecules of it, and there are two atoms of N per molecule of nitrogen gas.

 

As for the second question, 3.01 x 10^23 is half avogadro's number, meaning that many of something will be half its molecular weight times one gram. So take its molecular weight, divide by two, and the mass is that many grams.

Thanks for helping. I get it now. ^____^