Question

as a solid, Cr adopts a body-centered cubic unit cell. How many unit cells are present per cubic centimeter of Cr?

Answer 1

D(Cr) = 8,96 g/cm3 

M(Cr) = 63,546 g/mol 

 

In a cell face centred cubic, there are 4 atoms of Cur . . . ! 

n(Cr in 1 cm3) = m(Cu) / M(Cr) 
n(Cr in 1 cm3) = 8,96 / 63,546 
n(Cr in 1 cm3) = 0,141 mol of Cr 


Avogadro's number is : NA = 6,02•10^23 mol^-1 


N(Cr) = n(Cu) x NA 
N(Cr) = 0,141 x 6,02•10^23 
N(Cr) = 8,488•10^22 atoms of Cr 

N(cell) = N(Cu) / 4 
N(cell) = 8,488•10^22 / 4 
N(cell) = 2,122•10^22 cells in 1 cm3