Question

An alloy of Cu, Ag and Au is found to have copper in a CCP lattice. If the silver atoms occupy the edge centre and gold is present at the body centre, the alloy has a formula:

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

The number of Cu in the unit cell $=[(8\times \frac{1}{8})+(6\times \frac{1}{2})]=4$
The number of Ag in the unit cell $=(12\times \frac{1}{4})=3$
The number of Au in the unit cell = 1 (body center = 1)
The formula of the alloy = $C{u}_{4}A{g}_{3}Au$