Question

Examine the Fig.

1. Identify the separation technique marked as ‘S’.
2. Label the apparatus A, B and C.
3. Which of the following mixtures can be separated by the technique identified above? Use the data given in the Table. Mixtures:
   1. water - acetone
   2. water - salt
   3. acetone - alcohol
   4. sand - salt
   5. alcohol - chloroform
   6. alcohol - benzene

Boiling points of some compounds
Solvent	Water	Acetone	Alcohol	Chloroform	Chloroform
Temperature (°C)	100°C	56°C	78°C	61°C	80°C

Answer 1

(i) The separation technique marked as 'S' is distillation.

(ii) The labelled apparatus are:

• A - Distillation flask
• B - Water condenser
• C - Conical flask

(iii) Distillation is used to separate a liquid from a solution containing a dissolved solid, and it can also separate two miscible liquids if their boiling points differ by about 25 °C or more.

1. Water – acetone: The boiling points differ by 44°C (100 − 56). Since this is more than 25°C, these two liquids can be separated by distillation.
2. Water – salt: Salt is dissolved in water, so water can be obtained from the solution using distillation.
3. Acetone – alcohol: The difference in boiling points is 22°C (78 − 56). Since this is less than 25°C, simple distillation is not suitable.
4. Sand – salt: Both substances are solids, so distillation cannot be used to separate them.
5. Alcohol – chloroform: The boiling point difference is 17°C (78 − 61), which is below 25°C, so simple distillation is not effective.
6. Alcohol – benzene: The difference is only 2°C (80 − 78), so they cannot be separated by simple distillation.

Only mixtures (a) water–acetone and (b) water–salt solution can be separated using distillation.