Halogenoalkanes but mainly CFCs free radicals

Question 1

What are CFCs used for?

Answer 1

*Short chain CFCs are gases and used in aerosols propellants refrigerators
*Long chain CFCs are used as dry cleaning and de-greasing solvents

Question 2

What is a tertiary halogenoalkane

Answer 2

Three carbons attached to the carbon atom adjoining the halogen

Question 3

Give the general formula of Halogenoalkanes

Answer 3

CnH(2n+1)X
x= haloalkane

Question 4

Show reactions which show how chlorine atoms catalyse the decomposition of ozone

Answer 4

Cl* + O3 —> ClO* + O2
ClO* + O3 —> Cl* + 2O2

Question 5

Show the overall reaction for the decomposition of ozone

Answer 5

2O3–> 3O2

Question 6

Why have CFCs been banned

Answer 6

Beneficial to the environment as they decompose Ozone
Chemists have developed alternative chlorine free compounds

Question 7

Why is the hole in the ozone layer significant

Answer 7

Ozone absorbs harmful UV radiation and holes in the ozone layer increases the exposure of humans to UV which leads to sunburn, ageing of skin and skin cancer

Question 8

How does chlorine catalyse the decomposition of ozone?

Answer 8

The UV radiation causes the C-Cl bonds in the CFCs to break homolytically creating a chlorine free radical which reacts to ozone

Question 9

Initation with an example

Answer 9

Sunlight breaks the C_Cl bond in a CFC molecule and produces 2 radicals which will react with a molecule
CCl3F+hv–>CCL2F* + Cl*
hv= radiation

Question 10

Propagation

Answer 10

1. The Cl* reacts with O3 to form the ClO* intermediate and O2
2. The ClO* reacts with O3 to make 2O2 and Cl* as Cl* is reformed it acts as a catalyst

Question 11

Termination

Answer 11

2 radicals react with each other
Cl* +Cl* –>Cl2

Question 12

Overall reaction

Answer 12

2O3 –>3O2

Question 13

What are CFCs

Answer 13

Stable unreactive non toxic chemicals that wer eused in fridges as refirdgerant and as propellant in deodrants