Question

Q.4 Give reasons for the following statements:
[5]
1. If fractional distillation is carried out using a liquid-liquid mixture, one liquid will remain
in the flask & the other will be collected in the receiver.
2. Evaporation of a common salt solution or sea water, leaves behind common salt inside the
evaporating dish after heating.
3. Components in a mixture are present in varying proportions and not in a fixed proportion
4. Gunpowder is an example of a heterogeneous mixture.
5. In chromatography the absorbent medium e.g. Whatman filter paper is known as the-
stationary phase.
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Answer 1

Answer:

1) Fractional distillation is the process in which different liquids are heated and based on the different boiling points. ONe liquid will remain in flask while other will be collected in the reciever. The basic principle of this type of distillation is that different liquids boil and evaporate at different temperatures.

2) this is because when brine solution or salt solution is heated water starts evaporating leaving behind the solute as the residue. Salt cant evaporate with water as water has a comparatively lower boiling point than that of salt.

3) Mixture is the combination of compounds not pure elements. Mixtures are not formed by any sort of chemical bonding so the proportions don't matter in case of mixtures.

4) Gun powder contains sulfur ( S) , charcoal ( c) , and potassium nitrate (KNo3). Heterogeneous mixture is the one in which more than two things are mixed together and can be separated easily. It is a mixture of three component that can be separated easily so gun powder is a heterogeneous mixture

5) The Whatman Filter paper, which is made up of 99% Alpha cellulose, binds the water tightly to the paper and hence it is called the Stationary phase. In the Mobile phase, the solvents are partially mixed in the water and therefore it is called the Mobile phase.

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