The first compound C6H12 is cyclohexane and the other compound C6H6 is benzene. They are both aromatic compounds. Cyclohexane does not have double bonds in its ring while benzene has three double bonds in its ring. This is why the formula for cyclohexane contains 12 carbon atoms while benzene only has 6.
Answer: 19.4 g/cm3
Explanation: density is the relationship between mass over volume.
So density of gold is 15.7g/0.81cm3 = 19.4 g/cm3
The answer to your question would be silicon. I hope this helped!!!