Lab Manual: Separation of Mixture | Lab Manuals for Class 9 PDF Download

Objective

Theory

• Natural substances are not chemically pure. Different methods of separation are used to get individual components from a mixture. But, before separating any components from a mixture one must have sound knowledge of its physical and chemical properties so that separation can be done with ease.
• ]Sand, common salt and ammonium chloride form a heterogeneous mixture which can be separated easily through simple physical methods of separation.
• In the mixture given ammonium chloride is a sublimating substance. On heating the mixture, sublimating substance directly changes into gaseous state, its fumes are collected and cooled to get solid sublimate.
• To separate mixture of salt and sand following processes are used:
  • Dissolve the mixture in water → as one substance is soluble and the other (sand) is insoluble.
  • Sedimentation’ sand settles down at the bottom of the solution.
  • Filtration: salt + sand + water solution is filtered to separate sand particles completely from it.
  • Evaporation: The water from salt solution is evaporated by heating to get salt.

Materials Required
A China dish, tripod stand, a wire gauze, a bunsen burner, glass funnels, cotton, a glass rod, a beaker, filter paper, a clamp stand.

Chemicals Required
Sand, common salt, ammonium chloride (or camphor powder), and distilled water.

Procedure

1. Sublimation: Separation of ammonium chloride from the given mixture.

• Take a tripod stand, place a wire gauze over it.
• Keep the china dish with the given mixture on the wire gauze.
• Place the glass funnel in an inverted position on the mixture and plug the stem hole of the funnel with cotton.
• Heat the mixture with bunsen burner or spirit lamp, for few minutes (till you see white fumes released from the mixture).
• Turn off the burner and allow the fumes to collect on the inner side of the funnel.
• Remove the funnel to collect the deposited ammonium chloride on the funnel.
• Place the funnel again on the mixture, heat it and collect all the white fumes that comes out of the mixture. This procedure will continue till all the white fumes are collected and on further heating no more white fumes are released. The left out mixture has only salt and sand.

Separation of Ammonium Chloride

2. Sedimentation and Decantation/Filtration: Separation of sand from the mixture

• The mixture left in the last step of sublimation is transferred into a beaker.
• Add 5-10 mL of distilled water into the mixture (water should be sufficient to dissolve the salt into it) and stir it with glass rod.
• Make a cone of filter paper as shown in the diagram. Fix this cone in the glass funnel. Place the funnel over tripod stand or clamp it on the stand. Place a clean beaker under the stem of the funnel.
• Allow the mixture to stand so that sand particles settle down in the beaker.
• Now transfer the solution into the funnel with filter paper slowly for filtration.
• The residue collected on the filter paper is sand and the filtrate is salt solution.
• Collect the sand from the beaker and filter paper, dry it to get the sand completely separated from the mixture.

Dissolving the Mixture, Sedimentation and Decantation

Filter Paper Cone

Filtration of Sand & Salt Solution

3. Evaporation: Separation of common salt.

• The filtrate obtained in the beaker in previous step consists of common salt solution. Transfer it to the china dish.
• Place the china dish on tripod stand with bunsen burner and heat it in low flame (controlled heating) till all water gets evaporated.
• The salt is collected in the china dish, as all the water is evaporated.

Precautions

• Be careful during heating experiments.
• Prolonged heating should be avoided.
• Keep the flame low if you are using bunsen burner.
• Use clean and dry apparatus.
• Use distilled water for making solution.
• While filtering ensure that the filter paper cone does not tear up and allow the mixture to pass slowly through it.
• During sublimation, you can keep an extra plugged funnel to collect the dense white fumes.