QJEEM23Ch2137: JEE Main 2023 Chemistry - Class 12 JEEM23Ch2137 Solution: Iron oxide FeO, crystallises in a cubic lattice with a unit…

Question

Verified Solution • 2025–26 Session moderate

Iron oxide FeO, crystallises in a cubic lattice with a unit cell edge length of 5.0 Å. If density of the

\mathrm{FeO}

in the crystal is

4.0 \mathrm{~g} \mathrm{~cm}^{-3}

, then the number of

\mathrm{FeO}

units present per unit cell is __________. (Nearest integer)

Given: Molar mass of

\mathrm{Fe}

and

\mathrm{O}

is 56 and

16 \mathrm{~g} \mathrm{~mol}^{-1}

respectively.

\mathrm{N}_{\mathrm{A}}=6.0 \times 10^{23} \mathrm{~mol}^{-1}

Accepted Answer

$d = \frac{z \times m}{a^{3}}$

$4 = \frac{z \times 72}{6 \times 10^{23} (5 \times 10^{- 8})^{3}}$

$4 = \frac{z \times 72}{6 \times 125 \times 10^{- 1}}$

$= z \approx 4$

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