Question

Analysis shows that nickel oxide has the formula Ni_0.98O_1.00.What fractions of nickel exist as Ni²⁺and Ni³⁺ions?

Answer 1

Theformula of nickel oxide is Ni_0.98O_1.00.

Therefore,the ratio of the number of Ni atoms to the number of O atoms,
Ni: O = 0.98 : 1.00 = 98 : 100

Now,total charge on 100 O²⁻ions = 100 × (−2)

= −200

Letthe number of Ni²⁺ions be x.

So,the number of Ni³⁺ions is 98 − x.

Now,total charge on Ni²⁺ions = x(+2)

=+2x

And,total charge on Ni³⁺ions = (98 − x)(+3)

=294 − 3x

Since,the compound is neutral, we can write:

2x+ (294 − 3x)+ (−200) = 0

⇒ −x+ 94 = 0

⇒ x= 94

Therefore,number of Ni²⁺ions = 94

And,number of Ni³⁺ions = 98 − 94 = 4

Hence,fraction of nickel that exists as Ni²⁺=$\frac{94}{98}\times 100=95.9$ = 96%

And,fraction of nickel that exists as $N{i}^{3+}=\frac{4}{98}\times 100=4$%