Question

The structure of a crystalline lattice AB is rock salt type where B atoms are occupying all the CCP positions but A atoms are occupying all the octahedral voids -

• A. If atoms lying on one tetrad axis of symmetry are removed then molecular formula of the compound become AB
• B. If atoms lying on one triad axis of symmetry are removed then molecular formula of the compound become A4B5
• C. If atoms lying on one diad axis of symmetry are removed then molecular formula of the compound become A5B8
• D. All of the above molecular formula are correct corresponding to the defects mentioned

Answer 1

Answer: (D)

All of the above molecular formula are correct corresponding to the defects mentioned

Answer 2

The no. of A atoms remaining = 4 – 1 = 3

The no. of B atoms remaining = 4 – 2 × $\frac{1}{8}$

= 4 – $\frac{1}{4}$= $\frac{15}{4}$

Molecular formula is A₃B_15/4 º A₁₂B₁₅ º A₄B₅

The no. of A atoms

= 4 – 1 – 2 × $\frac{1}{4}$

= 4 – $\frac{3}{2}$= $\frac{5}{2}$

The no. of B atoms = 4

Molecular formula A_5/2B₄ or A₅B₈