[rhazen]

A unit cell of ZnSe has a density of 5.42grams per cubic cm. What is its edge length?  I have found the mass and volume...somehow, not to sure how I even managed that.  So. . . . . .how the heck do I find the length of a side given those variables?
Thanks for the help

[opti384]

What about the cell unit shape?

[rhazen]

it just gives me a diagram. The Se looks face centered, but there are 4 Zn molecules w/in the unit cell.

[cswarth]

I finished gen chem last spring so I have erase most of that sector of my memory already, but it seems to me you have all the information you need.

You have a diagram so you should be able to figure out how many atoms of each element you have in a unit cell, atoms/cell, which you can convert to moles/cell by dividing by Avogadros number.

You have density, g/cm^3

You also know the molecular weight, g/mole.

(g/mole) x (cm^3/g) x (mole/cell) = cm^3/cell.

(cm^3/g) is just 1/density.

answer = cube root of cm^3/cell.

Do you think that would work?

[sjb]

it just gives me a diagram. The Se looks face centered, but there are 4 Zn molecules w/in the unit cell.

Can you find any other sources with the structure of zinc selenide?

[rhazen]

I apologize for taking so long to respond.  Yes, that helped me alot.  Thank-you. Btw, 100/100 on my exam! Woohoo!  I like this forum.