4.1.2 Alkanes

Question 1

Are the carbon bonds in alkanes saturated or unsaturated?

Answer 1

Saturated, they have single C-C and C-H bonds.

Question 2

Describe the trend in boiling points of alkanes.

Answer 2

• As you increase the number of carbon and hydrogen atoms to have larger unbranched alkanes, the boiling point also increases due to the stronger london forces because there is more surface contact.
• Unbranched alkanes have lower boiling points than straight chain alkanes because they can not pack as easilywhich means less surface contact so therefore weaker London forces.

Question 3

What reactions can alkanes undergo?

Answer 3

• partial and complete combustion

- free radical substitution

Question 4

State the reagents and conditions needed for free radical substitution.

Answer 4

• UV light

- Chlorine molecule/ bromine molecule

Question 5

State the reagents and conditions needed for complete combustion

Answer 5

• Heat

- plentiful supply of oxygen

Question 6

Describe reactivity in alkanes.

Answer 6

• low reactivity due to high bond enthalpy and low polarity