# Question #70b01

##### 1 Answer

Where Z is the molecules per unit cell(dont confuse Z with atom per unit). Z is different for all different types of crystals. A BBC can contain 2 atoms(not molecules) per unit. A FCC can contain 4 atoms(again not molecules )per unit.

mol.wt is the molar mass

You can see what is a and loook carefully and observe that it can be seed that

So like we find out the volume ina cube

and

Z means the no. of atoms per unit. SO if we multiply itwith the molar mass we are actually getting the weight of the unit by measuring the weight of the total atoms in a mole of a unit cell

But why are are we multiplying it with Avogadro's constant?

This is because we want to to know the volume of 1mol.

So actually we can simplify the equation and can obtain

I know that there are no units in the equation but still cut out the same words

Finally we obtain

So we can be sure that this is a correct equation