A vessel of 50g mass was filled with water, and the mass of the vessel and its content were 125g. The water was emptied, and the vessel was filled with an unknown liquid, and the mass of the vessel and it contents was 110g. Can you address?

(i) what was the density of the unknown liquid;
(ii) what was the relative density of the unknown liquid?

1 Answer
Jul 8, 2017

We can infer IMMEDIATELY that the volume of the vessel is 75mL. Why?

Explanation:

Because we filled the vessel with (12550)g=75g water, which has a VOLUME of 75mL.

When it was filled with an unknown liquid, the volume of the liquid is still 75mL, but the MASS of the unknown liquid was 110g50g=60g, and thus its density, ρ, was massvolume = 60g75mL=0.80gmL1.

And thus ρrelative=ρsubstanceρwater=0.80gmL11.00gmL1=0.80, a dimensionless quantity as required.

Do you agree that this should float on water if it is immiscible with water......?

ρn-pentane=0.63gmL1........

ρn-hexane=0.65gmL1........

ρn-heptane=0.68gmL1........

ρn-octane=0.70gmL1........

ρn-butyl chloride=0.89gmL1........

ρisopropyl chloride=0.862gmL1........

I list the densities of some common water immiscible solvents for comparison.

On the other hand, ρethyl alcohol=0.79gmL1........Its density is certainly consistent (within experimental error) with that of the given liquid. Why can you argue that the unknown solvent is NOT ethyl alcohol?