What if both liquids can escape? — questions

1. explain

Choose the statement that explains what a fractionating column does. Explain why it improves separation without acting as a filter.

Circle one answer.

• The packing filters out B particles
• Repeated phase changes enrich the rising vapour
• Only A can vaporise below the pure boiling point of B

What happens on the packing?

Nudge (only if you are stuck): What can happen repeatedly on the packing? Can both liquids enter the vapour?

2. describe

Order the actions for collecting early and later fractions in separate receivers. Include the heat-off draining stages.

Write the number of each step in order.

1. Collect the early fraction
2. Switch off and let final drops drain
3. Exchange receiver after flow stops
4. Resume heat and collect later
5. Switch off, drain and cool before dryness

• First: ______
• Second: ______
• Third: ______
• Fourth: ______
• Fifth: ______

Nudge (only if you are stuck): Where should the last drops go before you exchange a receiver?

3. explain

An early fraction contains 8 A-units and 2 B-units. A later fraction contains 6 A-units and 4 B-units. Compare their composition and explain whether either is pure.

Compare the fractions

Assess the purity claim

Nudge (only if you are stuck): Compare each component with the total. Does ‘richer’ mean the other component is absent?

4. explain

Explain why the sidearm belongs above the packing. Explain why the thermometer bulb belongs beside that outgoing vapour path.

Nudge (only if you are stuck): If vapour could leave below the packing, which useful stage would it miss? What should reach the bulb?

5. explain

A pupil combines early and later fractions in one bottle. They claim the column has guaranteed pure A. Evaluate that claim and explain what combining the fractions changed.

Nudge (only if you are stuck): Did either fraction necessarily contain only A? What happens to their different compositions when mixed?