Lab 2: Simple Distillation

Question 1

Simple distillation

Answer 1

Allows desperation of various components of the mixture in acceptable purity if the difference between boiling points of each pure substance is greator than 50 degrees Celsius

Question 2

Non-volatile impurities present

Answer 2

Reduces the vapor pressure of the compound because it lowers the concentration of the volatile constitutent in the liquid phase.

Head temperature will be the same since the water condensing the thermometer bulb is now uncontaminated by the impurity

Pot temperature will be elevated owing to the decreased vapor pressure of the solution. As volatile component distills the concentration of impurity will increase. Further lowering partial pressure.

Question 3

Partition coefficient

Answer 3

Solute in stationary phase/ solute in mobile phase

Question 4

Gas chromatography

Answer 4

To separate mixtures of volatile compounds whose boiling points may differ by as little as .5 degrees Celsius.

Question 5

4 factors effect retention time in GC

Answer 5

1. Nature of stationary phase
2. Length of column
3. Temperature of column
4. Flow rate of inter carrier gas

Question 6

Nature of liquid stationary phase

Answer 6

Each liquid phase has a Max temperature limit above which it cannot be used. Temperature depends upon stability and volatility of liquid phase. At higher temperatures. Liquid phase vaporized and bleed from the column with the mobile phase. Like dissolves like. Non-polar compounds are best separated using non-polar liquid phase

Question 7

Temperature of column

Answer 7

Increasing temperature results in shorter retention times because the solubility of gases in liquids decreases with increasing temp. Partiton coefficients effected and bands move faster rate.

Question 8

Length of column

Answer 8

Resolution increases with increasing length and decreasing diameter. Increasing path length increases differences in retention times between bands and decreasing diameter narrow bands.

Question 9

Flowrates

Answer 9

Higher flowrates cause retention times to decrease.

Question 10

Percentage composition

Answer 10

Mol % compound = compound area (correction factor)/ all compounds area(correction factor)

Question 11

Thermal conductivity detectors

Answer 11

Since GC have this the thermal is different for each substance is slightly different so must be applied.

Question 12

Polarities are very similar

Answer 12

One that has longer retention time is the one with more molecular weight means higher intermolecular forces. Lower partial pressure and higher boiling point. Lower concentration in mobile phase and larger Kc