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KCET · Chemistry · Solid State

In chrysoberyl, a compound containing beryllium, aluminium and oxygen, oxide ions form cubic close packed structure. Aluminium ions occupy \(\frac{1}{4}\) th of octahedral voids. The formula of the compound is

  1. A \(\mathrm{BeAlO}_{4}\)
  2. B \(\mathrm{BeAl}_{2} \mathrm{O}_{4}\)
  3. C \(\mathrm{Be}_{2} \mathrm{AlO}_{2}\)
  4. D \(\mathrm{BeAlO}_{2}\)
Verified Solution

Answer & Solution

Correct Answer

(B) \(\mathrm{BeAl}_{2} \mathrm{O}_{4}\)

Step-by-step Solution

Detailed explanation

Given, chrysoberyl forms ccp structure.
Oxygen occupies lattice points \(=N\) (say)
Al occupies \(\frac{1}{2}\) of octahedral voids \(=\frac{N}{2}\)
Be occupies \(\frac{1}{8}\) of tetrahedral voids \(=\frac{2 N}{8}\)
\(\therefore\) The formula of compound is
\(\begin{aligned}
&\mathrm{Be}: \mathrm{Al}: \mathrm{O} \\
&\frac{2 N}{8}: \frac{N}{2}: N \\
&\Rightarrow \quad \mathrm{BeAl}_{2} \mathrm{O}_{4}
\end{aligned}\)