Question

According to X-ray measurements, the sides of a cubic unit cell of a metal crystal are a = 5.1 Å (1 angstrom = 10-8 cm). What is the density of the metal (g / cm3) which has a FCC (face centered cubic) crystal structure and the molecular weight 28.16 g / mol

Answer 1

Mass Density = volume Mass of a unit cell = mxn amu - Man - 6.022 x 23 grams m = molecular weight = 28-16 g/mol n= number of lattice points present in a unit cell for a Fcc crystal, n=4. volume = a3 = (side of unit cell) 3 cm3 volume = (s. 1x 183 cm3

28.16 g/mol X4 density = (Exot) 3 con? 6.022 x 1823 /mol / 112.64 g 1 6.022 X 123 132.651 x 1024 cm3 = = 112.64 g 79.8824322 cm? density = 1.41 g/cm3 Answer: density of the metal = 1.41 g/cm3