Posted by Jay on Monday, April 18, 2011 at 7:17pm.
Calcium fluoride is the wellknown mineral fluorite. It is known that each unit cell contains four Ca2+ ions and eight F ions and that the Ca2+ are arranged in a facecentered cubic lattice. The F ions fill all the tetrahedral holes. The edge of the CaF2 unit cell is 5.46295 x 10^8
cm in length. The density of the solid is 3.1805 g/cm^3. Use this information to calculate Avogadro's number.
I am completely lost on what to do. Here is what I have tried to do so far.
5.46295 x 10^8 cm (taken to the third power)= 4.63035 x 10^22 cm^3.
Then I utilized the density to convert to grams.
1.63035 cm^3 x 1g/3.1805 cm^3 = 5.1261 x10^23 grams
Here is where I get lost. I tried using the molar mass of CaF2, but it's not equal to Avogadro's number.
Any pointers would be greatly appreciated!
Thank you,
Jay

Chemistry  Jay, Monday, April 18, 2011 at 10:43pm
Oh just kidding after much frustration and stepping away from the problem and coming back, I noticed that I messed up the density in my conversion. I had the right idea I just had to correct my mistake and then continue on with the molar mass of CaF2, then I divided 4 molecules by the calculated moles, to get Avogadro's number.