Question

Consider a piece of gold jewelry that weighs 9.35 g and has a volume of 0.690 cm3 . The jewelry contains only gold and silver, which have densities of 19.3 g/cm3 and 10.5 g/cm3, 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

If there are g grams of gold, then add up the volumes (mass/density):

g/19.3 + (9.35-g)/10.5 = 0.690
g = 4.6
So, the % mass of gold is

4.62/9.35 = 0.49 = 49%