Question

When heated above 916ŗC, iron changes its bcc crystalline form to fcc without the change in the radius of atom. The ratio of density of the crystal before heating and after heating is [At . wt. Fe = 56]

• A. 1.069
• B. 0.918
• C. 0.725
• D. 1.231

Answer 1

Answer: (B)

0.918

Answer 2

r₁ = $\frac{2 \times 56}{\left( \frac{4r}{\sqrt{3}} \right)^{3}}$

r₂ = $\frac{4 \times 56}{\left( 2\sqrt{2}r \right)^{3}}$ \ $\frac{\rho_{1}}{\rho_{2}}$ = 0.918