In corundum, oxide ions have h c p arrangement. What percentage of octahedral voids are occupied by Al?

Question

In corundum, oxide ions have h c p arrangement. What percentage of octahedral voids are occupied by Al? (A) 33 % (B) 50 % (C) 66 % (D) 75 %

Tardigrade Admin · Accepted Answer

Corundum is Al 2 O 3. For 3 O 2- ions, octahedral sites are 3 . Out of three sites, only 2 are occupied by Al 3+ ions. ∴ Sites occupied by Al 3+ ions =(2/3) × 100=66 %

Q. In corundum, oxide ions have $h c p$ arrangement. What percentage of octahedral voids are occupied by $A l$ ?

$33%$

$50%$

$66%$

$75%$

Corundum is $A l_{2} O_{3}$ .

For $3 O^{2 -}$ ions, octahedral sites are 3 . Out of three sites, only 2 are occupied by $A l^{3 +}$ ions.

$∴$ Sites occupied by $A l^{3 +}$ ions $= \frac{2}{3} \times 100 = 66%$

Q. In corundum, oxide ions have hcp arrangement. What percentage of octahedral voids are occupied by Al?

33%

50%

66%

75%