Question

Analysis shows that nickel oxide has the formula Ni₀₉₈ O_1.00 What fractions of nickel exist as Ni²⁺ and Ni³⁺ ions?

Answer 1

The formula Ni₀₉₈ O_1.00 shows that Ni : O = 0.98 : 1.00 = 98 : 100. 

Thus, if there are 100 O-atoms, then Ni atoms = 98 charge on 100 O₂′ ions = 100 x (-2) = - 200 suppose Ni atoms as Ni²⁺ = x 

Then Ni atoms as Ni³⁺ = 98 - x 

Total charge on Ni²⁺ and Ni³⁺ 

= (+2) x + (+3) (98 - x) = 294 - x 

As metal oxide is neutral, total charge on cations = total charge on anions 

294 - x = 200 

x = 94 

∴ % of Ni as Ni²⁺ = gx100  98 

= 96% 

% of Ni as Ni³⁺ = 1000 - 96 = 4.