Chapter 3: Separation and Purification

Question 1

Facts on chromatography

Answer 1

1. The more soluble component travels faster and further up
2. Identical dyes travel up the same distance and produce the same colour when the same solvent is used
3. A pure substance shows one spot
4. Chromatography can be used to separate the components in a sample
5. Determine its purity
6. Separate and identify components in a sample
7. Determine the purity by checking for exact and constant melting or boiling point (A pure solid has an exact and constant melting point, a pure liquid has a exact and constant boiling point)
8. Determine the purity by chromatography
9. Impurities lower melting point and increase boiling point

Question 2

Chromatography
1. Explain why the starting line should be drawn using pencil and not in ink
2. Explain why the size of a sample placed onto the starting line should be small
3. Suggest why the solvent level should be below the starting line

Answer 2

1. The ink will dissolve in the solvent and will be separated
2. To prevent overlapping with neighboring dyes
3. The sample (spot) would dissolve in the solvent immediately and there is no separation

Question 3

Simple distillation
1. Why is the bulb of the thermometer placed near the outlet of the round bottom flask
2. How do we know that water is being distilled
3. What is the purpose of boiling chips
4. Why does cold water enter the condenser from the lower inlet instead of the upper
5. What is the function of a simple distillation process

Answer 3

1. To measure the temperature of the vapour before it leaves the flask
2. The thermometer will register a reading of 100
3. To ensure smooth boiling
4. To ensure efficient and effective cooling
5. To obtain a pure liquid