A-scientist was performing X-ray diffraction studies on a crystal having rock salt structure. The molecular mass of the.crystal ls` 239 gmol^-1`.The density of the crystal was found to be `12.7 gcm^-3` The scientist is supposed to study only those crystals having edge length below 0.75 mm. Show whether the crystal selected by the scientist was appropriate or not.

A crystal has an ordered arrangement of constituent particles:Copper crystal has a' face centred cubic lattice structure. Its density Is 8.93gcm^-3 . What is the length of the unit cell ? Atomic mass of copper is 63.5 gmol^-1 .

Density of a unit cell is the same as the density of the substance. So, if the density of the substance is known, we can calculate the number of atoms or dimensions of the unit cell. The density of the unit cell is related to its formula mass (M), number of atoms per unit cell (z), edge length (a in cm), and Avogadro's constant N_(A) , as rho=(zxxM)/(a^(3)xxN_(A)) Q. An element X crystallizes in a structure having an fcc unit cell of an edge 100 pm. if 24 g of the element contains 24xx10^(23) atoms, the density is