Q20 / 160 · AP EAMCET 2023 (17 May Shift 2) · Chemistry

The formula of nickel oxide is $\mathrm{Ni}_{0.98} \mathrm{O}_{1.00^{\circ}}$. What is the approximate percentage of $\mathrm{Ni}^{+2}$ in it?

  • A
    92
  • B
    94
  • Correct answer
    C
    96
  • D
    98

Solution

Let there be 100 formula units of $\mathrm{Ni}_{0.98} \mathrm{O}_{100}$. Thus, for $100 \mathrm{O}^{2-}$ ions, there are 98 nickel ions $\left(\mathrm{Ni}^{2+}\right.$ or $\left.\mathrm{Ni}^{3+}\right)$. Let $\mathrm{x}=$ number of $\mathrm{Ni}^{2+}$ ions. $\Rightarrow$ Number of $\mathrm{Ni}^{3+}$ ions $=98-\mathrm{x}$. For an electrically neutral compound:- $\begin{aligned} & 2 x+3(98-x)+100(-2)=0 \\ & \Rightarrow x=94\end{aligned}$ So, $\%$ of $\mathrm{Ni}^{2+}=\frac{94}{98} \times 100=96 \%$

Hence, the correct answer is option: 'C'.

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