Question

A necklace contains 4.85g of gold, 1.25g of silver, and 2.40g of copper. What is the mole fraction of each metal?

Answer 1

Answer:

Explanation:

1

% by mass = 0.45 x 100/ 0.45 + 250= 0.180

2

moles NH4Cl = 90.0 g/ 53.4917 g/mol=1.68

M = 1.68/ 2.25 = 0.747

3

moles HNO3 = 63 g / 63 g/mol= 1.0

m = 1.0 mol/ 0.500 Kg = 2.0

4

moles Au = 4.85 g /196.967 g/mol=0.0246

moles Ag = 1.25 g / 107.868 g/mol=0.0116

moles Cu = 2.40 g / 63.546 g/mol=0.0378

total moles = 0.0740

mole fraction Au = 0.0246 / 0.0740 = 0.332

mole fraction Ag = 0.0116/ 0.0740=0.157

mole fraction Cu = 0.0378 / 0.0740=0.511

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