Question

How can we separate a mixture of sand, petrol, and kerosene?

Answer 1

Step 1 Separation of insoluble sand from a mixture of miscible liquids: To separate sand from the miscible kerosene and petrol mixture by passing it through a filter paper or by decantation.

Step 2: Separation of miscible liquids

• When a mixture contains two or more miscible liquids whose boiling points differ by at least 15°C then these are separated by using the fractional distillation method. In this method, a fractionating column is used in the distillation apparatus. A fractionating column is a glass tube fitted with glass beads.
• The main purpose of using a fractionating column is to provide more cooling area and to provide obstructions to the ascending vapours and descending liquid.
• A round bottom flask fitted with a fractionating column is fitted in an iron stand and it is kept on a tripod stand with wire gauze.
• A thermometer is fitted in the upper part of the fractionating column and its side tube is fitted with a Liebig's condenser.
• Water is circulated continuously in Liebig's condenser to cool the vapours.
• The distillates are collected in different containers (conical flasks).

An apparatus for fractional distillation is shown in the figure below.

Step 3: Conclusion

• In this method, the kerosene and petrol mixture is placed in a distillation flask with a thermometer attached.
• The mixture is progressively heated; because petrol has a lower boiling point than kerosene, it will first vaporise and condense in the water condenser.
• The condenser outlet is used to collect the condensed petrol, while the distillation flask is used to collect the kerosene.