[ericbmd]

On a recent trip out of country a chemistry professor found a foldent colored metal coin at 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 18.82g and raised the water level in the cylinder from 5.2 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.


I'm not sure what to do??

[Will]

My guess is that you need to work out the density of the coin- you know that it is 2.1cm³ and weighs 18.82g. Then you need to compare it to the density of gold, which should be quoted to you. A source that I found says pure gold has a density of 19.3gcm^-3.

I found the density of the coin to be 8.962gcm^-3 which is signifacantly below that of pure gold.

Funilly enough copper happens to have a density of 8.96gcm^-3 so I would guess that was the main constituent of the coin (which would probably be gold coated, which is why the density is only slightly higher).

[Borek]

density of gold, which should be quoted to you

Which you have to look up. Or you remember that it is in the range of 20 g/mL, much heavier then most other metals.