Question

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

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

Answer 1

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

Effective no. of $Cu$ atoms in a unit cell $=8\times \frac{1}{8}+6\times \frac{1}{2}=1+3=4$
Effective No. of Ag atoms in a unit cell $=12\times \frac{1}{4}=3$
Effective no. of Au atoms in a unit cell=1
So, general formula of compound is $C{u}_{4}A{g}_{3}Au$