posted by Jay on .
Calcium fluoride is the well-known 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 face-centered 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!
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.