An element has hcp packing with a hexagonal unit cell. Its density is 4.5 g/cm3 and the unit cell volume is 3.53 x 10-23 mL. Calculate the molar mass (g/mol) of the element to three significant figures.

Answer 1

The mass = volume x density
You know the volume of the unit cell and the density; therefore, you can calculate the mass of the unit cell.
Divide the mass of the unit cell by the number of atoms per unit cell to obtain the mass a single atom; then multiply by Avogadro's number to arrive at the molar mass. Post your work if you get stuck. Your text or notes should contain information for the number of atoms per unit cell as well as the value to use for Avogadro's number.

Answer 2

90