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Chemistry=MOLES!

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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.

  • Chemistry=MOLES! -

    <<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.

  • Chemistry=MOLES! -

    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.

  • Chemistry=MOLES! -

    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.

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