I am struggling with this AP Chemistry word problem

Question

A 255mL round-bottom flask is weighed and found to have a mass of 114.85g. A few mL of an easily vaporized liquid are added to the flask and the flask is immersed in a boiling water bath. All of the liquid vaporizes at the boiling temperature of water, filling the flask with vapor. When all of the liquid has vaporized, the flask is removed from the bath, cooled, dried and reweighed. The new mass of the flask and the condensed vapor is 115.23g. Which of the following compounds could the liquid be? (Assume the ambient pressure is 1.0atm)

 

A. C2H5OH

 

B. C4H10

 

C. C2H6

 

D. C4H9OH

 

E. C3H7OH

Answer 1

115.23 g - 114.85 g = 0.38 g = mass of condensed vapor

PV = nRT

n = PV/RT = (1.0 atm)(0.255 L)/(0.0821 Latm/Kmol)(373K)

n = moles = 0.00833 moles

molar mass = 0.38g/0.00833 moles = 45.6 g/mole

molar mass A =47 g/mole

molar mass B = 58 g/mole

molar mass C = 30 g/mole

molar mass D = 74 g/mole

molar mass E = 69 g/mole

 

Most likely candidate would be (A) C2H5OH = ethanol