Q. Ice crystallises in a hexagonal lattice having the volume of a unit cell as 132x10^-24. If the density is 0.92g/cm^3 at a give temp., Then the number of H2O molecules per unit cell is:- Options: 1. 1 2. 2 3. 3 4. 4 -------------------------------------- According to the solution, the value of Z has been found. But we know that Z is the number of atoms, which is 4 for hcp. Then how come Z is taken as number of 'molecules' of H2O ??