Chem help? I don't know how to do this..?

Question

31. A sample of 6.68 g of calcium combines exactly with 6.33 g of fluorine, forming CaF2. Find te relative amss of the atoms of calcium and fluroine. Check your answer using a table of atomic weights. If the formula were not known, could you still do thid calculation?

Okay, I don't know what this question is asking... Is it as easy as I think it is? Best answer goes to the one who tells me how I should go about doing this.

Answer 1

Sounds like percent composition.  First, calculate FORMULA mass of CaF2 (Ca = 40.078 or just 40); F = 18.998 (or 19); CaF2 has ONE mole of Ca and TWO moles of F:  [40 x 1] + [19 x 2] = 78.  You can also do this: 6.68 g of Ca is how many MOLES of Ca?  Well, that's 6.68/40.08 = 0.167 moles of Ca.  6.33 g of F is how many MOLES of F?  That's 6.33/18.99 = 0.33 moles.  Hmm, Isn't 0.167 moles of Ca just about ONE-HALF of 0.33 moles of F?  I think your teacher is asking you this...that 0.167 moles of Ca are combining with 0.333 moles of F, which is a 1:2 ratio.