Question

The cubic unit cell of rhenium trioxide (Reo,) his Re atoms at the corners and O atoms on each of the 12 edges. The atoms touch along the edges. The radi are Re 137 pm and O 73.pm. What is the density of Reo,? a. 2.55 g/cm 420m b. 2.94 g/cm3 C. 3.49g/cm cll Reaton 12o 5.25 g/cm e. 7.52 g/cm -21

Answer 1

ReO_3 the cubic unit cell contain 8 Re atoms at the corner so, the total no. of effective Re atoms in the unit cell = 1/8 times 8 = 1 because A_3 corner atom is shared by 8 unit cell There are twelve 0 atoms at the edges of the unit cell so, the total no. of effective 0 atoms in the unit cell = 1/4 times 12 = 3 because A_3 edge atom is shared by 4 unit cell so, the effective no .of ReO_3 molecule in the unit cell (z) = 1 The molar mass of ReO_3 M = {182.2 + (16 times 3)} g/mol = 230.2 g/mol \r\n Given the radii of Re and 0 atoms as below - gamma_Re = 137 Pm gamma_0 = 73 pm therefore Edge length of the unit cell, a = gamma_Re + 2 gamma_0 + gamma_Re a = {137 + (2 times 73) + 137} pm = 420 times 10^-