Sterling silver is a solid solution of silver and copper. if a piece of a sterling silver necklace has a mass of 105.0g and a volume of 10.12 ml, calculate the mass percent of copper in the piece of necklace. assume that the volume of silver present plus the volume of copper present equals the total volume.

Density for Cu: 8.96 g/ml 
Density for Ag: 10.5g/ml

First set up an equation: mass = density * volume 

8.96 * x + 10.5* (10.12 - x) = 105.0 

The density of the Cu (8.96) times x (the amount of copper) added to the density of Ag (10.5) times voume of silver (10.12 - the amount of copper) should equal the total weight. 

Solving for x:

x = 0.818 mL 

So 
mass of copper = 8.96 * .818 = 7.33 
mass percent of copper = 7.33/105 * 100% = 6.98%

a. the law of proportion states the combination of 2 atoms in a specific ratio to produce multiple compounds such as the given statement of question ‘1st compound contains 88.8 % cu ’ indicates 88.8 g of cu is present along with 11.2 g oxygen in 100 g of compound whereas the statement ‘2st compound contains 79.9 % cu ’ indicates 79.9 g of cu is present along with 20.1 g oxygen in 100 g of compound

1st compound contains 88.8 g cu

for cu

m = 63 g /mol

atomic % = 88.8 /63 = 1.42

for o

m = 16 g /mol

atomic % = 11.2 /16 = 0.7

b. the emperical formula of 1st compound is

cu1.4o0.7

cu2o