3.15 Alcohols

Question 1

Alcohols (4)

Answer 1

• All alcohols contain an -OH group.
• All alcohols have the general formula CnH2n+1 OH.
• The first four alcohols in the homologous series are methanol, ethanol, propanol and butanol.
• The basic naming system for alcohols is the same as for alkanes - but replace the final ‘-e’ with ‘-ol’.

Question 2

What are the three properties of alcohols?

Answer 2

• They are flammable.
• They are soluble.
• They can be oxidised to form carboxylic acids.

Question 3

What do alcohols’ flammability mean?

Answer 3

They can undergo complete combustion.

Question 4

What do alcohols’ solubility mean?

Answer 4

They can dissolve in water to form solutions. As alcohols aren’t acidic or alkaline, their solutions will have a neutral pH.

Question 5

Uses of alcohols (2)

Answer 5

• Alcohols (e.g. methanol and ethanol) are used as industrial solvents that are miscible in water. (Miscible liquids are liquids that can dissolve in each other). This is because they can dissolve most things water can dissolve, but they can also dissolve substances that water can’t dissolve - e.g. hydrocarbons, and lipid compounds like oils and fats.
• The first four alcohols are also used as fuels. For example, ethanol is used as a fuel in spirit burners - it burns fairly cleanly and doesn’t smell.

Question 6

What can alcohols be oxidised with?

Answer 6

Oxygen or with a type of chemical called an oxidising agent.

Question 7

What is methanol oxidised to form?

Answer 7

Methanoic acid

Question 8

What is the general formula for alcohols?

Answer 8

CnH2n+1OH