If you are given the number of molecules in an unidentified chemical compound, can you calculate the number of moles in this sample?
yes, because you know that each mole contains 6.02 x 1023 molecules
yes, as long as you can also measure the mass of the sample
no, because the number of moles depends on the volume of the sample
no, because the number of moles depends on the identity of the substance

the volume of fluid displaced would equal the volume of the gas. use a gas syringe - this is a laboratory instrument that can be used to withdraw a certain volume of gas from a closed system or to measure the volume of gas from a chemical reaction.

the density of gold = 19.3 g/cm3

the relation between density and mass and volume is

density = mass / volume

given :

mass of gold = 13 g

density = 13g / volume = 19.3

volume = 13 /19.3 = 0.67 cm^3

thus volume of gold nugget = 0.67 cm^3