Alcohols

Question 1

Volatility of Alcohol

Answer 1

The first few members of the alcohol homologous series are volatile liquids at room temperature and pressure due to their low boiling point.

Question 2

Solubility of alcohols

Answer 2

Alcohols are soluble in water. This is due to the hydroxyl group in the alcohol which is able to form hydrogen bonds with water molecules. Alcohols with a shorter hydrocarbon chain are very soluble. As the length of the hydrocarbon chain increases, the solubility in water decreases.

Question 3

Chemical Properties of Alcohols

Answer 3

Alcohols are effectively neutral. The -OH group is not alkaline.

Question 4

Combustion of Alcohol

Answer 4

Alcohols undergo complete combustion in excess oxygen to produce carbon dioxide and water vapour.

Question 5

Is combustion of alcohol exothermic?

Answer 5

Yes, it is highly exothermic. Hence, they are used as fuels.

Question 6

Alcohol undergoes oxidation.

Answer 6

Yes, they are oxidised by atmospheric oxygen or oxidising agent

Question 7

Why does alcoholic drinks turn sour when exposed to air?

Answer 7

Alcohol is oxidised by atmospheric oxygen in presence of certain bacteria.

Question 8

Oxidation of Alcohol using Oxidising Agent

Answer 8

Reagent: Acidified aqueous potassium manganate (VII)
Reaction condition: Heat under reflux
Observation: Purple solution decolourise

Question 9

Oxidation of Primary alcohol

Answer 9

Primary alcohol oxidises into carboxylic acid

Question 10

Oxidation of secondary alcohol

Answer 10

Alcohol oxidises into ketone

Question 11

Oxidation of tertiary alcohol

Answer 11

Alcohol does not oxidise.

Question 12

Production of ethanol by fermentation of glucose

Answer 12

Reagent: Glucose
Reaction conditions: yeast, 37•C, absence of oxygen
Products: Ethanol and Carbon dioxide

Question 13

Why specifically 37•C?

Answer 13

I f the temperature is raised beyond 37•C, the enzymes in yeast will be denatured and unable to catalyse the reaction. Fermentation will stop.

Question 14

Why is there a need to stopper the reaction flask?

Answer 14

To ensure the absence of oxygen in order to prevent the oxidation of ethanol into ethanoic acid by bacteria from the air.

Question 15

Why is there a need to stopper the reaction flask?

Answer 15

It is to ensure the absence of oxygen in order to prevent the oxidation of ethanol into ethanoic acid by bacteria in the air.

Question 16

What is the function of the limewater?

Answer 16

The limewater acts as an airlock to allow carbon dioxide escape and to prevent oxygen from entering the setup.

Question 17

Why a higher alcohol content cannot be produced?

Answer 17

It causes the yeast to die and fermentation to stop.

Question 18

How do we extract the ethanol?

Answer 18

Through fractional distillation.

Question 19

Uses of alcohol

Answer 19

1. In alcoholic drinks
2. As a solvent in paints, varnishes, deodorants, perfumes, colognes
3. As fuels