Mole Concept: how it applies to alloys
One mole is a number, not a mass.

See the following figurative example:

Let's say we are dealing with a sample of pure chemistry books.


A book's weight is 1 kg.
One mol of books would be 6,022 × 10²³ books.
The mass of one mol of books (the molar mass of books) would be as follows:


1 kg (mass of one book) × 6,022 × 10²³ (# of books)

Now let's say we're dealing with a mixture (alloy) of 60% chemistry and 40% history books. What is the mass of 1 mol of this mixture?


A history book's weight is 2 kg


So, our entire collection of books, sum up to Avogadro's number = 6,022 × 10²³ units. And we know that it is 60% Chem. and 40% Hist. So the mass of the entire collection would be:

m = N × 0,6(1kg) × 0,4(2kg)

where N is the Avogadro's number.



Enough of analogies. You have the mass of the gold and palladium atoms from the periodic table. I am assuming you also have the proportion Au/Pd.

You also know that there's 1 mol of atoms. The exact same equation would apply:

m = N × P.M(Au) × P.M(Pd)

where N is the Avogadro's number, P and M are the percentages and atomic mass, respectively, of gold and palladium.