Question

Calculate the number of impurities per centimeter cube present in copper 99.999% pure. Hint:
Consider all the impurities as substitutional. Data: Copper has an FCC structure and a lattice
parameter of a=0.36151nm.

Answer 1

% of purity = 99.999 %

which means for every 10,000 atoms we had 99,999 Cu atoms and 1 other atom

now for FCC , number of atoms per unit cell = 4

cell length = 0.36151 nm = 0.36151 x 10^ -9 m = 0.36151 x 10^ -7 cm

unit cell volume = a^3 = ( 0.36151 x 10^-7)^3 cm^3 4.7245554 x 10^ -23

now for 4.7245554 x 10^-23 cm3 we had 4 Copper atoms

For 1cm^3 we have ( 4 /4.724554x10^-23) = 8.466405 x 10^22

Now for every 10,000 we had 1 impurity

hence for every ( 8.466405 x 10^22) copper atoms number of impurities = ( 8.466405x10^22) / ( 10,000)

                                   = 8.466405 x 10^18