yellow-gold is an alloy that is 75% gold 16% silver and 9% copper (by mass). calculate the cost of gold in a cube of the alloy 1 ft on a side

Answer 1

You have to look up a price for gold per gram. You also need the density of gold, silver, and copper (I am not sure if this was actually intended by the instructor. Otherwise, you would have to be given the density of the alloy and the density of gold)

In order to get the gold volume per volume of alloy you need to do the following:

Assume 100 g of alloy: 75 g of Au 16 g Ag 9 g Cu

The volume of each: 75/ρ_Au 16/ρ_Ag 9/ρ_Cu ρ's in g/cm³ (assuming volume conserved)

Total volume of 100g of Alloy: sum of the volumes above

volume fraction of gold: (15/ρ_Au)/(75/ρ_Au+16/ρ_Ag+9/ρ_Cu)

Now s = 1 foot*(12 in/ft)(2.54 cm/in) = cm

V = s³ in cm³

Value of gold = Volume*(Volume fraction of gold)(density of gold)(cost of gold/gram)

Good luck! Please consider a tutor. You can google all the values I mentioned.