# NEET Chemistry The Solid State Questions Solved

A spinel is an important class of oxides consisting of two types of metal ions with the oxide ions arranged in ccp layers. The normal spinel has 1/8th of the tetrahedral void occupied by one type of metal and one half of the octahedral voids occupied by another type of metal ions. Such a
spinel is formed by $Z{n}^{2+}$, $A{l}^{3+}$ and ${O}^{2-}$ with $Z{n}^{2+}$ in tetrahedral void. Give the simplest formula of the spinel.

(A) $ZnA{l}_{2}{O}_{4}$

(B) $ZnA{l}_{2}{O}_{3}$

(C) ZnAlO

(D) None of these

(A). Let the no. of tetrahedral voids = a
No. of octahedral voids = a/2
1/8 th tetrahedral voids is occupied by $Z{n}^{2+}$

1/2 of octahedral voids occupied by $A{l}^{3+}$

Ratio of $Z{n}^{2+}:A{l}^{3+}$

1  : 2

For 1 mol

Total +ve charge = 2+3$×$2=8

$\therefore$ The simplest formula will be $ZnA{l}_{2}{O}_{4}$

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