Question
An ionic compound is formed by elements X and Y. Element Y forms a face-centered cubic (FCC) lattice, and element X occupies one-third of the tetrahedral voids. What is the formula of the compound?
MHT CET
Chemistry
Solid State
2026
MHT CET 2026 (13 April Shift 2)
MHT CET Chemistry Question (2026) — Solution
Options
- A. X_2Y_3
- B. XY
- C. XY_3
- D. X_2Y
Answer
A. X_2Y_3
Step-by-step solution
Element Y forms a face-centered cubic (FCC) lattice. Number of Y atoms per unit cell = 4 Number of tetrahedral voids in an FCC unit cell = 2 4 = 8 Element X occupies one-third of the tetrahedral voids. Number of X atoms per unit cell = 1 3 8 = 8 3 Ratio of X to Y = 8 3 : 4 = 8 : 12 = 2 : 3 The formula of the compound is X_2Y_3.
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