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# An alloy of Copper , Silver , and Gold is found to have Copper constituting the C.C.P lattice. If Silver atoms occupy the edge centres and Gold is present at body centre , the alloy will have the formula:

$(a)\;Cu_4 Ag_2 Au\qquad(b)\;Cu_4Ag_4 Au\qquad(c)\;Cu_4 Ag_3 Au\qquad(d)\;Cu Ag Au$

Effective no. of Cu atoms in a unit cell $=8\times\large\frac{1}{8}+6\times\large\frac{1}{2}$
= 1+3 = 4
Effective No. of Ag atoms in a unit cell = $12\times\large\frac{1}{4}$
$\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;= 3$
Effective no. of Au atoms in a unit cell = 1
So, general formula of compound is $Cu_4Ag_3Au$