Formula of nickel oxide with metal deficiency defect in its crystal is Ni₀.98O. The crystal contains Ni²⁺ and Ni³⁺. ions. The fraction of nickel existing as Ni²⁺ ions in the crystal is (NEET (Odisha) 2019)

Let, in the given crystal 0.98 Ni O 2 3 Ni xand Ni 0.98 x Total charge on 2 M and 3 M 2 x 3 0.98 x 2x 2.94 3x 2.94 x As metal oxide is neutral. Therefore, total charger on cations. = total charger on anions. 2.94 – x =2 [ charge of oxygen atom = -2] X = 2.94 – 2 = 0.94 So, the fraction of Ni²⁺ ions in the crystal 0.94 0.959 0.96 0.98