a) $0.65\ g/cm^3$ b) No. c) No. d) Possibly 2-methylpentane.
Work Step by Step
a) Sample's mass: 3.2745 g, volume: 5.0 mL, so the density is: $\rho=m/V=0.65\ g/cm^3$ b) There's a tecnhical tie between two of them, but in practice all the options are too close to this value to make an accurate assesment. c) Technically hexane, 2,3-dimethylbutane and 2-methylpentane (all of which have a density of 0.66 g/cm³ when rounded to 2 significant figures), but in practice no, because they are all too close. d) With the new volume of $4.93\ mL$: $\rho = 0.664\ g/cm^3$ This points to 2-methylpentane, but it's still too close to hexane and 2,3-dimethylbutane to be decisive.