4.1.2

Question 1

Why are alkenes relatively unreactive

Answer 1

The C–C and C–H bond enthalpies are relatively high so require a lot of energy to break

Question 2

What type of IMF do alkanes have

Answer 2

London dispersion forces (they are non-polar)

Question 3

What happens to bp as alkane chain length increases

Answer 3

Increases as there is more surface area so more LDF. More energy is required to break the bonds

Question 4

What is the equation of complete combustion

Answer 4

Alkane + Oxygen —-> Carbon dioxide + Water

Question 5

What is the equation of incomplete combustion

Answer 5

Alkane + Oxygen —-> Carbon/ carbon monoxide + Water

Question 6

What are the 3 steps of free radical substitution

Answer 6

Initiation- forms 2 free radicals
Propagation- FR + molecule —> FR + molecule
Termination- FR + FR —> molecule

Question 7

What are the steps of free radical substitution in the synthesis of bromoethane

Answer 7

I) BR-BR —> 2BR•
P) C2H6 + BR• —> •C2H5 + HBr
•C2H5 + Br2 —> C2H5Br + Br•
T) •Br + •BR —> Br2
•C2H5 + • C2H5 —> C4H10
•C2H5 + •Br —> C2H5Br

Question 8

What conditions does initiation require

Answer 8

UV light

Question 9

What are the problems with free radical substitution

Answer 9

Has a low atom economy
It is hard to predict the final product
It can happen at any point of the carbon chain