Iron exhibits bcc structure at room temperature. Above 900^ , it transforms to fcc structure. The ratio of density of iron at room temperature to that - Chemistry MCQ NEET (UG) 2018 2026 | ExamTest.live

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Iron exhibits bcc structure at room temperature. Above 90 0^{\circ} C, it transforms to fcc structure. The ratio of density of iron at room temperature to that at 90 0^{\circ} C is:

Solution & Step-by-step Explanation

Density ρ = \frac{Z \cdot M}{a ^{3} \cdot N _{A}} . Assuming M and r are constant: ρ \propto \frac{Z}{a ^{3}} .BCC: Z = 2, a_{b cc} = \frac{4 r}{3} . ρ_{1} \propto \frac{2}{( \frac{4 r}{3} ) ^{3}} = \frac{2 \cdot 3 3}{64 r ^{3}} .FCC: Z = 4, a_{f cc} = 22 r . ρ_{2} \propto \frac{4}{( 2 2 r ) ^{3}} = \frac{4}{16 2 r ^{3}} .Ratio: \frac{ρ _{1}}{ρ _{2}} = \frac{6 3}{64} \times \frac{16 2}{4} = \frac{3 3}{4 2} .

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Iron exhibits bcc structure at room temperature. Above 90 0^{\circ} C, it transforms to fcc structure. The ratio of density of iron at room temperature to that at 90 0^{\circ} C is:

\frac{3 3}{4 2}

\frac{4 3}{3 2}

\frac{3}{2}

\frac{1}{2}

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