Question

Consider a piece of gold jewelry that weighs 9.50 g and has a volume of 0.685 cm^3 . The jewelry contains only gold and silver, which have densities of 19.3 g/cm^3 and 10.5 g/cm^3, respectively. If the total volume of the jewelry is the sum of the volumes of the gold and silver that it contains, calculate the percentage of gold (by mass) in the jewelry.

Answer 1

let G equal volume of gold , and S equal volume of silver

G + S = 0.685 cm^3

19.3 G + 10.5 S = 9.50 g

solve the system for the volume of gold (G)
... multiply by the density to find the mass

Answer 2

Let x = mass Au,
then 9.50-x = mass Ag.
---------------------
(1)--volume Au = m/d = x/19.3
(2)--volume Ag = m/d = (9.50-x)/10.5
(3)--volume Au + volume Ag = 0.685
---------------------------------

Substitute (1) and (2) into (3), solve for x and 9.50-x, then
mass % Au = (mass Au/9.50)*100 = ?
mass % Ag = (mass Ag/9.50)*100 = ?

Answer 3

You have the system. Work it to find the answer. You should be thankful you have been given the equations to solve the problem.