What is the formula of the magnetic oxide of cobalt, used in recording tapes, that crystallizes with — Solid State Chemistry Question

💡 Solution & Explanation

Let oxide ions be $N$. Tetrahedral voids = $2N$, octahedral voids = $N$. Co in tetrahedral = $\frac{1}{8} \times 2N = \frac{N}{4}$. Co in octahedral = $\frac{1}{2}N$. Total Co = $\frac{N}{4} + \frac{N}{2} = \frac{3N}{4}$. The ratio of Co:O is $\frac{3}{4} : 1 = 3 : 4$. The formula is Co$_3$O$_4$. Therefore, correct answer is D.