Organic Chemistry Distillation Quiz (Lab 1)

A student has a solution, containing 4 liquids of similar chemical composition and BP that differ by no more than 15C. The student performs a fractional distillation, collecting at a rate of 3 drops a second, but further analysis shows poor separation of the compounds. Which of the following factors would most improve separation?

Decrease the rate of heating

Separation of the components of a mixture is achieved in this experiment via:

Distillation

During a fractional distillation of 2 liquids with similar BP, a sharp temperature drop is observed. What explains this observation?

The lower boiling point liquid has distilled out

Continuing to heat the round-bottom flask even after the distillation process has completed does not simply cause disappearance of the compound mixture, but can also be dangerous. Why?

1. The glass may overheat and shatter 2. The residue cakes onto the flask and can't be easily scrubbed free 3. Peroxides may form 4. The flask may explode

Regardless of whether you are performing simple or fractional distillation, the number of clamps that are suggested to properly secure the apparatus is:

2

A simple distillation of a 1:1 mixture of cyclopentane (BP: 49C) and hexane (BP: 68.7C) is carried out. As the temperature is increased, the liquid composition within the distilling flask is expected to show a(n)

Increase in hexane mole fraction

What is the purpose of adding clamps between connections of different parts of glassware?

To provide additional structural support

What is the main difference between simple and fractional distillation set-ups?

The distance between the round-bottom flask and distillation head (Fractional uses vigreux column)

A student carries out a simple distillation on a known compound with a BP of 135C, but distillate drops did not appear in the condenser until a temperature of 152C. Gas chromatography confirms the substance was pure and the thermometer was properly calibrated. What procedural error in the setting up of the distillation apparatus would most likely explain this discrepancy?

The thermometer bulb placement was too low in the distillation flask

True or False: Slow heating of the distillation flask is required in distillation because rapid heating can cause interrupted distillation collection

True