QAIPMT-2004-Ch-2577: NEET 2004 Chemistry - Class 12 AIPMT-2004-Ch-2577 Solution: A compound formed by elements X and Y crystallizes in a cubic…

To determine the formula of the compound formed by elements X and Y based on their positions in a cubic structure, we need to count the number of atoms per unit cell for each type of atom and then simplify the ratio. For element X: Corners of a cube: Each corner atom is shared by 8 adjacent cubes, so each corner contributes 1/8 of an atom to the cube. Since there are 8 corners in a cube, the total contribution from corners is 8 _ 1 8 = 1 $8 \times \frac{1}{8} = 1$ 8 _ 8 1 _ = 1 atom of X per unit cell. For element Y: Face-centers of a cube: Each face-centered atom is shared by 2 adjacent cubes, so each face-center contributes 1/2 of an atom to the cube. Since there are 6 faces on a cube, the total contribution from face-centers is 6 _ 1 2 = 3 $6 \times \frac{1}{2} = 3$ 6 _ 2 1 _ = 3 atoms of Y per unit cell. Therefore, within one unit cell, we have 1 atom of X and 3 atoms of Y, giving us the simplest ratio of X : Y = 1 : 3 $X:Y = 1:3$ X : Y = 1 : 3 . Hence, the formula of the compound is X Y 3 $XY_3$ X Y 3 _ . So, the correct answer is: Option A: XY 3