Orgo lab techniques: Simple distillation

What is the vapor pressure of a liquid?

the pressure exerted by the vapor above the liquid

tendency for a liquid to vaporize

volatility

Volatile liquid

has higher vapor pressure

Less volatile liquid

has lower vapor pressure

At what point does a liquid boil?

temperature at which the vapor pressure of the liquid is the same as the atmospheric pressure

In a mixture of miscible liquids, at which temperature does the solution boil?

occurs at a temperature between the boiling points of the two pure liquids.

How does the composition of the distillate change over time during a distillation of a mixture of liquids?

Early on: distillate is rich with the more volatile component

Middle: distillate contains a mix of the two components

end: distillate is rich with the less volatile component

How is a vapor-liquid equilibrium diagram used to determine the composition of the liquid and vapor in a distillation?

shows change in both the composition of the liquid in the flask and the distillate over the course of the distillation

bottom curve describes the boiling point of the liquid in the flask as it relates to its composition

top curve describes the temperature of the vapor as it relates to its composition- basically the compostition of the distillate

When is simple distillation used?

boiling point difference must be at least
25°C to ensure effective and accurate separation of the two liquids

When does boiling occur?

When the energy gained by a liquid overcomes the intermolecular interactions in the liquid phase

When the total vapor pressure of the substance is equal to the atmospheric pressure

vapor pressure

The total pressure of a vapor in equilibrium with its liquid phase.

Miscible liquids

The components form a homogeneous solution

The partial pressure of each component is the vapor pressure of the component multiplied by the mole fraction of the component

Each component exerts its own vapor pressure

When setting up a distillation apparatus, which port on the condenser serves as the water inlet?

The port farthest from the round-bottom flask

its UPWARDS

Cyclohexane and toluene have boiling points of 80.8 °C and 110.6 °C, respectively. If distilling a mixture of these two compounds, which will distill first?

Cyclohexane

What must be done when assembling the distillation apparatus to prevent the loss of vapor?

Apply vacuum grease to all of the joints.

In a simple distillation setup, what is the sequence of equipment from the bench top to the round bottom flask?

Lab jack, stir plate, heating mantle