How Do You Calculate Molar Mass from BCC Packing?

[vipertongn]

Homework Statement

An element has bcc packing with a body-centered cubic unit cell. Its density is 862 kg/m^3 and the unit cell volume is 1.51 x 10-28 m^3. Calculate the molar mass (g/mol) of the element to three significant figures.

Homework Equations

Known: D= 862 kg/m^3, V=1.51 x 10-28 m^3 , MM=??

The Attempt at a Solution

Ok the correct answer is 39.2, but I don't know how to arrive to that answer.

(862kg/m^3)(1.51e-28m^3)(1000g/1kg)(6.022e23atoms/1mol)(1/2 atoms)
(0.68) but instead I get 26.6504.

The 0.68 is the density packing.

 

[Borek]

The 0.68 is the density packing.

Are you sure it is relevant to the question?

 

[vipertongn]

ah, htat wasn't required, thanks

 

[Borek]

The real question is: do you understand what you did and why?

 

[vipertongn]

Yes, I pretty much converted to the proper units I needed, the only problem was getting the right units.