18-Karat Gold vs. 14-Karat Gold

18-Karat Gold vs. 14-Karat Gold

Gold in its pure form is too soft to be used for most jewelry. Therefore, the gold is mixed with other metals to produce an alloy. The composition of gold alloys are always calculated by mass, using the karat (kt) as a unit of measure. A karat represents a proportion by mass of one part in twenty-four. The higher the karat value, the higher the proportion of gold in relation to the total metal content. Pure gold is therefore 24 karat, while an 18-karat gold alloy contains (at least) 18 parts (by mass) of gold out of 24 parts total.




In a sample of 18-karat gold, 75 percent of the total mass is pure gold, while the rest is typically 16 percent silver and 9 percent copper. If the density of pure gold is ρgold=19.3g/cm3, while the densitites of silver and copper are respectively ρsilver=10.5g/cm3and ρcopper=8.90g/cm3, what is the overall density ρ18kt of this alloy of 18-karat gold?

ANSWER = 15.6  

The percentage composition by mass of the less expensive 14-karat gold is typically 58.5 percent gold, 4.0 percent silver, 31.2 percent copper, and 6.3 percent zinc.

Find the percentage composition by volume of 14-karat gold. The density of zinc is ρzinc=7.14g/cm3

ANSWER = 39,5,45,11