When you collected 50 mL of distillate in the collection flask, the mole percent of water in the distillation flask decreased to approximately 20 mole percent.
With your simple distillation set-up, what percentage of water will be in the vapor phase at this composition of the liquid?
Read the theory page if you don't remember how to interpret the boiling point composition curve:
a) 98 mole percent water
b) 86 mole percent water
c) 92 mole percent water
d) 72 mole percent water