A compound formed by elements X & Y. Crystallizes in the cubic structure, where X is at the corners of the cube and Y is at the six face centres. What is the formula of the compound? If side length is 5A^(@), estimate the density of the solid assuming atomic weight of X and Y as 60 and 90 respectively.

A compound formed by elements X & Y. Crystallizes in the cubic structu

1.	A compound formed by elements X & Y. Crystallizes in the cubic structure, where X is at the corners of the cube and Y is at the six face centres. What is the formula of the compound? If side length is 5A^(@), estimate the density of the solid assuming atomic weight of X and Y as 60 and 90 respectively.
Answer» Solution :From eight corner atoms one atoms (X) contribute to one unit cell. From six face centres, three atoms (Y) contribute to one unit cell. So, the formula of the COMPOUND is `XY_(3)`. As we know that, `rho =(n xx M_(m))/(N_(A) xx a^(3))`, here n=1 MOLAR mass of `XY_(3)` `M = 60 + 3 xx 90 = 330` gm `rho =(1 xx 300)/(6.023 xx 10^(23) xx (5 xx 10^(-8))^(3)) gm//cm^(3)` `a = 5A = 5 xx 10^(-6)` cm `=(330)/(6.023 xx 10^(23) xx 125 xx 10^(-34)) gm//cm^(3) = 4.38 gm //cm^(3)`