JEE Main · 2022 · 27 Jun 2022 · Shift 1 · Solid State

Metal deficiency defect is shown by

Fe_{0.93} O

. In the crystal, some

Fe^{2 +}

cations are missing and loss of positive charge is compensated by the presence of

Fe^{3 +}

ions. The percentage of

Fe^{2 +}

ions in the

Fe_{0.93} O

crystals is ______. (Nearest integer)

Answer: 85

Solution

In Fe₀.₉₃O, the formula indicates 0.93 moles of Fe per mole of O. To maintain charge neutrality with O²⁻, let x be the fraction of Fe³⁺ and (0.93-x) be the fraction of Fe²⁺. Charge balance: 2(0.93-x) + 3x = 2(1). Solving: 1.86 - 2x + 3x = 2, so x = 0.14. Therefore, Fe²⁺ = 0.93 - 0.14 = 0.79. Percentage of Fe²⁺ = (0.79/0.93) × 100 = 84.9% ≈ 85%.

JEE Main · 2022 · 27 Jun 2022 · Shift 1 · Integer answer

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