Book 1

Question 1

Substances that sublime

Answer 1

Iodine
Ammonium chloride
Iron(iii) chloride
Sulphur
Benzoic

Question 2

Fractional distillation

Answer 2

Fractional distillation
Simple distillation cannot be used to separate a mixture of two or more miscible liquids. Fractional distillation is used to separate a mixture of two or more miscible liquid with relatively close boiling point into its component fractions.

A fractionating column is introduced between the distilating flask and the condenser. This is where the actual separation occurs. Vapours with higher boiling points would condense as they enter the upper portion. The fractional distillation process is repeated until all the components fractions in the mixture are distilled over.
This method is used to separate crude oil or petroleum into its component fractions such as natural gas, petrol, kerosene, gas oil, heavy oil and bitumen. It is also used obtain pure nitrogen from air.

Question 3

In crystallization, the salt solution is first heated to evaporate some of the solvent. The solution becomes saturated. When the saturated solution is cooled, crystals of the solute begin to form. Examples of such salts are:

Answer 3

CuSO4.5H20,
Cu(No3)2.3H20,
FeS04.7H20,
Zn(NO;)2.6H20, MgS04.7H20 etc.

Question 4

Distillation

Answer 4

Used to recover a solvent from a solution
Different boiling point

Question 5

Density

Answer 5

Mass/volume

Question 6

Factors that affect density determination

Answer 6

Temperature
Air bubbles
Air pressure
Viscosity
Specific gravity

Question 7

PURE AND IMPURE SUBSTANCES

Answer 7

Impurities lower the melting point of a substance and raises the boiling point. The melting and boiling point of a given pure substance is fixed at a particular temperature.

Question 8

Commonest absorbent medium for chtomatography

Answer 8

Filter paper

Question 9

Simple distillation

Answer 9

Large difference in boiling point

Question 10

Bioling point of water

Answer 10

Boiling point determination is used to ascertain the purity of water. Pure water boils at 100°C.
The use of CuSO, and COCl, are used to determine the presence of water. Water changes the colour of CuSO4 from white to blue. If COCl is used the colour changes from blue to pink.

Question 11

Rubber latex and vulcanizer solution are

Answer 11

Mixtures

Question 12

Sand bath

Answer 12

Used to bring about steady rate in evaporation