Question

Formula of nickel oxide with metal deficiency defect in its crystal is $A_{0.8}O$. The crystal contains $A^{2+}$ and $A^{3+}$ ions. The fraction of nickel existing as $A^{2+}$ ions in the crystal is

• A. 0.96
• B. 0.04
• C. 0.5
• D. 0.31

Answer 1

Answer: (C)

0.5

Answer 2

So the ratio of $A : O =80: 100$ Thus, if there are 100 atoms of oxygen then 80 atoms of $A$. Let $x$ be the no. of atoms of $A ^{+2}$. No. of atoms of $A ^{+3}=80- x$ Charge on A = Charge on O Since oxygen has charge $-2$. Therefore, $\begin{array}{l} 2 x+3(80-x)=2 \times 100 \\\ 2 x+240-3 x=200 \\\ \Rightarrow x=40 \end{array}$ Therefore, Fraction of $A ^{+2}=\frac{\text { Atoms of } A ^{+2}}{\text { Total no. of atoms }}$ $\Rightarrow$ Fraction of $A ^{+2}=\frac{40}{80}=0.50$