Question

An alloy of copper, silver and gold is found to have copper constituting the ccp lattice. If silver atom occupy the edge centres and gold is present at body centre, Calculate the formula of alloy:

• A. $C{u}_{4}A{g}_{4}Au$
• B. $C{u}_{4}A{g}_{2}Au$
• C. $C{u}_{4}A{g}_{3}Au$
• D. $CuAgAu$

Answer 1

The correct option is C $C{u}_{4}A{g}_{3}Au$

In each unit cell, Cu atoms are in ccp latice so total no of atom,
$\Rightarrow 8\times \frac{1}{8}+6\times \frac{1}{2}=4$

Ag atoms are in edge centre,
$\Rightarrow 12\times \frac{1}{4}=3$

Au atoms are in body centre,
$\Rightarrow 1\times 1=1$

$\therefore$ Formula is $C{u}_{4}A{g}_{3}Au$.