Calculate the theoretical density of NiO given that it has t

Calculate the theoretical density of NiO, given that it has the rock salt crystal structure. You may want to use the table below. The atomic weights for Ni and O are 58.69 g/mol and 16.00 g/mol, respectively. Rho = g/cm^3 The number of significant digits is set to 3; the tolerance is +/-3%

Solution

The density = Rho = n\' ( A_n1 + A₀) / V_c N_A ; A_ni = 58.69 g/mol and A ₀ = 16.00 g/mol,

NA = Avogadro\'s number ( atoms mol ^-1 )

\'Sincen the crystal structure is rock salt n\' = 4formula units per unit cell. . Using the ionic radii for Ni²⁺ and O^2- , the unit cell volume is computed as follows:-

Vc = (2r_Ni² + + 2r_O^2-) ³ = { 2( 0.069nm) + 2( 0.140nm)}³

   = 0.0730 nm3/unit cell = 7.3 x 10 ^-23 cm³/unit cell

Thus the theoritical density Rho =

( 4 formula units /unit cell ) ( 58.69 g/mol = 16.00 g/mol) / ( 7.3x 10^-23 cm³/unit cell )( 6.023x10²³ formula units /mol)

= 6.79gm/cm³