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 has a formula

• A. $Cu\, Ag\, Au$
• B. $Cu_{4}Ag_{2}Au$
• C. $CuAg_{3} Au$
• D. $Cu_{4}Ag_{4}Au$

Answer 1

Answer: (C)

Number of $Cu$ atoms at corners $=8 \times \frac{1}{8}=1$
Number of $Ag$ atoms at edge centers $=12 \times \frac{1}{4}=3$
Number of Au atoms at body center $=1 \times 1=1$
$\therefore $ Formula is $CuAg _{3} Au$.