A compound formed by elements X and Y crystallizes in the cubic structure, where X is at the corners of the cube and Y is at the six face centers. If side length is 5 Ao, estimate the density of the solid assuming atomic weight of X and Y as 60 and 90 respectively.

From eight corner atoms one atom (X) contributes to one unit cell.From six face centers, three atoms (Y) contribute to one unit cell.So, the formula of the compound is XY3.As we know that,ρ=n×MmNA×a3, here n=1Molar mass of XY3Mm = 60 + 3 × 90 = 330 gρ=1×3306.023×1023×5×10−83g/cm3a=5Å=5×10−8cm=3306.023×1023×125×10−24g/cm3=4.38g/cm3