In the video, the water level was 15 milliliters before adding the chain, and 20 milliliters after adding the chain. When I weighed the chain, its mass was 73.5

Question

I believe the chain is solid metal (not gold plated), but is probably a blend of gold and other metals. I looked up that gold has a density of 19.3 g/ml, while the other metals like silver and copper usually blended with gold have a combined density of about 9.7 g/ml.

Determine what percentage of the chain is gold, by mass, to at least 1 decimal place?

Answer 1

You left out the units of mass for the unknown metal.  I'll assume it is grams (g), or 73.5 g

The displaced volume is 20 ml - 15 ml = 5 ml

mass of gold = G

mass of blend = B

G g/19.3 + B g/9.7 = 5 ml ... equation 1

Since mass of chain = 73.5 g, then G + B = 73.5 g ... equation 2

Solve these 2 simultaneous equations and find G (mass of gold) = 50.3 g (to 1 decimal)

% gold by mass = mass of gold/mass of chain (x100%)

% gold by mass = 50.3g/73.5g (x100%) = 68.4%