May I please have some Chemistry help?

Question

1) Which substance would have greater density, 5g of rubber stopper or 5g of copper?

2) Determine the volume of lead if its mass was 250 grams

3) The density of gold is 19.32 g/ml. Find the volume of a 30g sample of gold.

4) A person brings you a substance that has a mass of 75 grams and a volume of 3.22 ml. The person claims that teh substance is pure gold. How could you prove or disprove this persons claim?

THANK YOU!! :D

Answer 1

1) Copper is denser than rubber by huge margin.  You shouldn't even have to look this one up, but might want to get values for the densities just to placate your teacher.

2) The density of Pb is 11.34 g/mL, so we divide 250g by this to get the volume in mL: 22.0mL of lead.

3) This is the same as the lead problem, only with different numbers.  We know the density and the mass, just find the volume.  Try to do this one on your own.

4). As stated in the previous question, the density of gold is 19.32g/mL.  Density is mass divided by volume, so the density of this substance is 75g / 3.22mL = 23.29g/mL.  This is a different density than that of gold.  So it is not pure gold, but don't go throwing that metal away just yet!  The densest metal, osmium, has a density of 22.61g/mL, so either this person has a very new and special material unknown to physics, lives at extreme pressures, or I have made a mistake (but since I checked my math, and this is a textbook question, you may as well go with the implausible answer).