The pyknometric density of sodium chloride crystal is

2.165 x  10³  kg m ^-3  while  its  X – rays density is  2.178 x 10³ kg m ^-3 . The fraction of unoccupied sites in sodium chloride crystal is

a. 5. 96 x 10^-3

b. 5.96

c. 5.96 x 10^-2

d. 5. 96 x 10 -1

Ans. a

Explanation : Difference = 2.178 x 10³  – 2.165 x 10³   = 0.013 x 10 ³

Fraction unoccupied = 0.013 x 10 ^-3  / 2.178 x 10³      = 5.96 x 10 ^-3

(14)