Question

-Analysis shows that nickel oxide has the formula $N{i_{0.98}}{O_{1.00}}$. What fractions of nickel exist as $N{i^{2 + }},N{i^{3 + }}$ ions?

Answer 1

At first think about the chemical formula of nickel oxide. The chemical formula of nickel oxide is $NiO$. In the chemical formula of nickel oxide nickel exists in $+ 2$ oxidation state and oxygen exists in $- 2$ oxidation state.

Complete step by step answer:
-In the question, we have given that nickel oxide has the formula $N{i_{0.98}}{O_{1.00}}$.
As per the given formula, nickel has $98$ ions for $100$ oxide ions.
Out of $98$ ions , let us take $x$ ions are in $+ 2$ oxidation state. Then automatically the total number of ions in $+ 3$ oxidation state are $98 - x$.
Oxide ion has a $- 2$ oxidation state.
To maintain electrical neutrality, the total positive charge on cations $=$ total negative charge on anions.
The sum of oxidation states of a molecule is equal to zero.
In the given formula, the number of nickel ions present in $+ 2$ oxidation state are $x$, $+ 3$ oxidation state are $98 - x$ and the oxide ions in its $- 2$ oxidation state are $100$.
The overall equation is,
$2x + 3(98 - x) + 100( - 2) = 0 \\\ x = 294 - 200 \\\ x = 94 \\\$
The total number of nickel ions in $+ 2$ oxidation and $+ 3$ oxidation state are $94$ and $4$ respectively for $100$ oxide ions.
fraction of $N{i^{ + 2}}$ions =$\dfrac{{94}}{{98}} = 0.96$
fraction of $N{i^{ + 3}}$ions$= \dfrac{4}{{98}} = 0.04$
Hence, the fractions of nickel that exist as $N{i^{ + 2}}$and $N{i^{ + 3}}$ are $0.96$ and $0.04$ respectively.

Additional Information:- Nickel oxide is the principal oxide of nickel. It is classified as basic metal oxide. It is a green crystalline solid. Nickel oxide adopts the sodium chloride structure with octahedral $N{i^{ + 2}}$and ${O^{ - 2}}$ sites. Nickel oxide is also a component in the nickel-iron battery, also known as the Edison battery. It is a component in fuel cells. It is the precursor to many nickel salts. Heating nickel oxide with either hydrogen, carbon or carbon monoxide reduces it to metallic nickel. It combines with the oxides of sodium and potassium at high temperatures to form the corresponding nickelate.

Note:
The chemical formula of nickel oxide is $NiO$ because the fraction of nickel ions in $+ 2$ oxidation state dominates the fraction of $N{i^{ + 3}}$ ions. So the nickel exists in $+ 2$ oxidation state in its chemical formula.