Question

A 67.2 g sample of a gold and palladium alloy contains 2.85×1023 atoms . What is the mass percentage of the gold and palladium?

Answer 1

A 67.2 g sample of a gold and palladium alloy contains 2.85×1023 atoms . What is the mass percentage of the gold and palladium?

Given that,

A 67.2 g sample of a gold and palladium alloy contains 2.85×1023 atoms

We know that One mole of atoms contains 6.022x10^23 atoms.

Firat calculate the moles of sample =
2.85 x 10^23 / 6.022x10^23 = 0.473mole of atoms.

Molar mass of gold = 197 g/ mole means
1 mole of gold = 197.0 g

Molar mass of Pd = 106.4 g/ mole

Means
1 mole of palladium = 106.4 g

mole Au + mole Pd = 0.473

mole Au = 0.473 – mole Pd

mole Au x 197 + mole Pd x 106.4 = 67.2 g

[0.473 – mole Pd ] x 197 + mole Pd x 106.4 = 67.2 g

93.18- 197 mole Pd -106.4 mole Pd =67.2 g

93.18-90.6 mole Pd = 67.2

25.98 = 90.6 mole Pd

Mole Pd = 0.288

mole Au = 0.473 – mole Pd

mole Au = 0.473 – 0.288

= 0.185 mole

grams Au = 0.185 x 197 = 36.445 g
36.445 / 67.2 *100= 54.2% Au)

grams Pd = 0.288 x 106.4 = 30.64 g
30.64 / 67.2 *100= 45.6% Pd)