On a recent trip out of the country a chemistry professor found a golden-colored
ID: 725028 • Letter: O
Question
On a recent trip out of the country a chemistry professor found a golden-colored metal coin at a flee market. The person selling the coin priced it at $200, claiming it was pure gold. Being a well-equipped traveler and a chemist, the professor produced his graduated cylinder and electronic balance. The coin had a mass of 18.82 g and raised the water level in the cylinder from 5.2 mL to 7.3 mL. Show, by calculation, why he declined to purchase the coin. What, do you think, the major constituent of the coin was ? Justify your answer.Explanation / Answer
density = 18.82 g / (7.3 mL - 5.2 mL) = 8.96 g/mL from here http://en.wikipedia.org/wiki/Gold the density of gold is 19.6 g / cm^3 = 19.6 g/mL ********* so obviously the coin wasn't pure gold.. so what element has density = 8.96 g/mL? Well it could be one of several things. or even an alloy...here's some possibilities... copper has density = 8.94 g/mL.. so a gold plated copper coin would have density about 8.96 g/mL Nickel has density = 8.91 g/mL..same thing... and a nickel copper alloy should have density about 8.93 or so g/mL etc..