Formula of nickel oxide with metal deficiency
defect in its crystal is Ni2.980. The crystal
contains Ni2+ and Ni3+ ions. The fraction of nickel
existing as Ni2+ ions in the crystal is
(1) 0.31
(2) 0.96
(3) 0.04
(4) 0.50
Answers
Answer:0.96
Explanation: Let the fraction of metal which exists as Ni2+ ion be x.
The fraction of metal as Ni3+=0.98
So , 2x +3(0.98-x)=2
2x+2.94-3x=2
x= 0.94
Fraction of Ni2+= 0.94/0.98=0.96
Given:
The formula of nickel oxide with metal deficiency defect in its crystal is Ni₀.₉₈O.
The crystal contains Ni²⁺ and Ni³⁺ ions.
To Find:
The fraction of nickel existing as Ni²⁺ ions in the crystal
Solution:
The fraction of nickel existing as Ni²⁺ ions in the crystal is (2) 0.96.
Oxides of elements that have cations in more than one oxidation state are known as mixed oxides.
In Ni₀.₉₈O, Ni exists as both Ni²⁺ and Ni³⁺, hence it is a mixed oxide.
Electrical neutrality is always maintained in such compounds i.e. the total charge on anions must be equal to the total charge on cations.
From the molecular formula, we can conclude that 0.98 Ni ions are required to neutralize 1 oxide ion.
Let there be y number of Ni²⁺ ions
⇒ The number of Ni³⁺ ions = 0.98 - y
The charge on an oxide ion is -2
Hence the net charge from Ni ions must be +2
According to the given information,
2 X (y) + 3 X (0.98-y) = 2
or 2y + 2.94 - 3y = 2
or -y = -0.94
or y = 0.94
Hence, out of 0.98 Ni ions, 0.94 ions are in the +2 oxidation state.
So the fraction of nickel existing as Ni²⁺ ions in the crystal = 0.94 / 0.98
= 0.959
≈ 0.96