Iron crystalises in FCC with an edge length of 400 pm . If it contains $0.1 \%$ Schottky defects, calculate its approximate density

[Atomic weight of $\mathrm{Fe}=56 \mathrm{~g} / \mathrm{mol}$ ]

At atmospheric pressure and very low temperature, water crystallises to

Intercepts of a plane in crystal is given by $a, b / 2,3 c$ in a simple cubic unit cell. The miller indices are

A cubic structure is formed where atoms of element $X$ are occupied at corner of cube and also at face centers. Atoms of element $Y$ are present at body center and at the edge centers. If all the atoms are removed along a plane passing through the middle of the cube (bisecting the four edges), the formula will become