Chemistry=MOLES!
posted by Justin .
I'm having trouble converting moles to grams and finding the mass of molecules.
Problems I'm stuck on:
What is the mass in grams of .99x10^49 Sodium Chloride Molecules?
and How many moles of Cu are in 9.61 grams?
and How many moles are in 5.94x10^45 Ne atoms?
I just really need to know how to solve these. Thanks.

<<What is the mass in grams of 0.99x10^49 Sodium Chloride Molecules?>>
First find out how many moles that is by dividing by Avogadro's number, 6.02*10^23 molecules/mole. You get 1.64*10^25 moles. Then multiply that result by 58.5 gm/mole, the molar mass of NaCl.
You will get a very large number, comparable to the mass of the Earth. Are you sure you copied the problem correctly?
<<How many moles of Cu are in 9.61 grams?>>
Divide by the atomic mass of Cu, 63.5 g/mole
<<How many moles are in 5.94x10^45 Ne atoms?>>
Multiply that by the atomic mass of Neon, which it would be a good idea to look up, so that you get some practice doing this sort of thing. 
The two pertinent pieces of information are here.
mols = grams/molar mass
There are 6.02 x 10^23 anythings in a mol; therefore,
mols = # atoms/6.02 x 10^23
or
mols = # molecules/6.02 x 10^23
Let me know if this doesn't help but explain in detail what the problem is. 
Well, you know that twelve of anything is a dozen of them.
In exactly the same way, 6.022*10^23 of atoms or molecules is a mole of them.