3.2.3 Synthesis of CFCs

Question 1

Photochemical reactions

Answer 1

Reactions started by UV light

Question 2

Free radical substitution

Answer 2

Cl or Br replaces Hydrogen atom

Question 3

Free radical

Answer 3

Particles with an unpaired electron

Question 4

How are free radicals formed

Answer 4

A covalent bond splits equally and one electron goes to each species

Question 5

Free radicals
reactivity
reason

Answer 5

very reactive

unpaired electron

Question 6

Stages in synthesis of a chloroalkane

3

Answer 6

initiation
propagation
termination

Question 7

Initiation stage

Answer 7

(photo dissociation)
free radicals are produced
sunlight provides energy for this to happen
UV present

Question 8

Propagation stage

Answer 8

(chain reaction)
free radicals used up and created
continues until all Cl2 or CH4 used up

Question 9

Substitutions

middle step

Answer 9

chlorine in excess = hydrogen atoms replaced by chlorine

methane in excess = chlorine used up quickly

Question 10

Termination stage

Answer 10

(free radicals used up)

2 free radicals form a covalent bond which makes it a stable molecule

Question 11

CFCs

Answer 11

chlorofluorocarbons

all hydrogen atoms replaced by chlorine and fluorine atoms

Question 12

Ozone

Answer 12

O3

Question 13

The ozone layer

Answer 13

in the upper atmosphere, absorbs UV light from sun

Question 14

Which bonds in CFCs break in ozone

how

Answer 14

c-cl
broken by UV
free radical catalysts

Question 15

Safer alternative to CFCs

Answer 15

HFCs

Question 16

CFCs
properties
3

Answer 16

unreactive
non-toxic
non-flammable

Question 17

CFCs

cause

Answer 17

damage to the ozone layer

Question 18

CFCs
used in
4

Answer 18

aerosols
foams
refrigerants
solvents