Question

At $T(K)$, copper (atomic mass $=63.5u$ ) has fcc unit cell structure with edge length of $x\mathring{A}$. What is the approximate density of $Cu$ in $gc{m}^{-3}$ at that temperature? $\left(N_A=6.0\times 10^{23}mo{l}^{-1}\right)$

• A. $\frac{42.3}{x^3}$
• B. $\frac{4.23}{x^3}$
• C. $\frac{423}{x^3}$
• D. $\frac{212}{x^3}$

Answer 1

Answer: (C)

Given,

fcc unit cell is present, $Z=4$

Edge length $=x\mathring{A}$

Atomic weight $=63.5gmo{l}^{-1}$

$\because$ Density, $d=\frac{Z\times \text{ atomic weight }}{a^3\times N_A}$

where, $a=$ edge length

$d=\frac{Z\times \text{ atomic weight }}{x^3\times 6.023\times 10^{23}\times {\left(10^{-8}\right)}^3}$

$=\frac{4\times 63.5}{x^3\times 6.023\times 10^{23}\times 10^{-24}}$

$d=\frac{423.0}{x^3}$