Methods Of Purification

Question 1

Separating liquid and insoluble solid

Answer 1

Filtration

Insoluble solid is residue
Liquid collected is filtrate

Question 2

Separate solvent (which does not decompose on heating) from solution

Answer 2

Evaporation to dryness

Question 3

Separate solvent (whose solubility varies with temp) from solution

Answer 3

Crystallization

Heat to saturation
Cool and allow substance to crystallize

Question 4

Separate solid that sublimes from solid mixture. Give examples

Answer 4

Sublimation

Iodine
Naphthalene (found in moth balls)

Question 5

Separate miscible liquids with large difference in boiling points

Answer 5

Simple distillation

Question 6

Separate miscible liquid mixture with small difference in boiling points

Answer 6

Fractional distillation

Eg crude oil, liquid air and fermented liquor

Question 7

Use of fractioning column

Answer 7

In fractional distillation, the vapor produced is a mixture. Fractioning column helps to separate into individual components

Question 8

Separation of Immiscible liquids

Answer 8

Separating funnel

Question 9

Separating small quantities of mixture

Answer 9

Paper chromatography

Question 10

Principle of paper chromatography

Answer 10

The mixture is separated based on differences in solubility in a particular solvent

Question 11

Calculating Rf value

Answer 11

Distance moved by component from starting line

Over

Distance moved by solvent from starting line

Question 12

Results of paper chromatography

Answer 12

One spot: pure substance
More spots: mixture
No spots: no soluble substance in solvent

Question 13

Effect of impurities on melting and boiling

Answer 13

Lower melting point
Increase boiling point

cause melting and boiling to take place over a range of temperatures

Question 14

Effect of pressure on melting and boiling point

Answer 14

Pressure increases melting and boiling points

Exception: with water pressure decreases melting and boiling points