Theoretical Density Calculations of NiO with Rock Salt Crystal Structure

How to calculate the theoretical density of NiO with a rock salt crystal structure?

Given that Ni²⁺ has a cation radius of 0.069 nm and O²⁻ has an anion radius of 0.140 nm, what is the theoretical density of NiO?

Final answer:

The theoretical density of NiO with a rock salt structure is determined by calculating the edge length of its unit cell from given radii of Ni and O ions and then substituting all values into the density equation.

The theoretical density of a substance can be calculated using the formula: ρ = Z*M / (NA*Vc), where ρ is the density, Z is the number of formula units per unit cell, M is the molar mass, NA is Avogadro's number, and Vc is the volume of the unit cell.

For NiO with a rock salt structure, Z = 4 as there are four formula units per unit cell. The molar mass of NiO is calculated as the sum of the molar masses of Ni (58.69 g/mol) and O (16.00 g/mol), resulting in 74.69 g/mol.

The unit cell edge length (a) is calculated using the formula a = 2*(rcations + ranions), which in this case is 2*(0.069 nm + 0.140 nm) = 0.418 nm.

Converting the edge length to cm gives a value of 0.418 x 10^-7 cm. The volume of the unit cell (Vc) is then calculated as a^3, resulting in (0.418 x 10^-7)^3 cm^3.

Substitute all values into the density formula to determine the theoretical density of NiO in g/cm³.