Organohalogen compounds in the environment

Question 1

Uses of organohalogen compounds 3

Answer 1

Dry cleaning solvent
Flame retardant
Refrigerants

Question 2

Where is the ozone layer

Answer 2

Outer edge of stratosphere

Question 3

Function of ozone layer

Answer 3

Absorbs high energy radiation (UVB)

Question 4

Risks of exposure to UVB

Answer 4

Skin cancer, eye cancer, crop damage

Question 5

What does CFCs stand for

Answer 5

Chlorofluorocarbons, containing Cl, F and C

Question 6

Properties of CFCs and why

Answer 6

Stable: chemically inert, non toxic, low flammability
Due to strength of carbon halogen bonds

Question 7

What do CFCs break down into upon reaching the stratosphere and what affect do the products have

Answer 7

Chlorine radicals, which catalyse the breakdown of the ozone layer

Question 8

Steady state?

Answer 8

When rate of forwards is equal to that of reverse so concs stay approx constant but not in a closed system

Question 9

Adv and Dis of HCFCs

Answer 9

A: Breakdown more easily than CFCs, in the troposphere
D: Still contain Cl, Cl radicals form if reach stratosphere bc contains Cl

Question 10

Adv and Dis of HFC

Answer 10

A: No Cl
D: Expensive to produce

Question 11

Adv and Dis of hydrocarbons

Answer 11

A: Can be used as propellant in aerosols, cheap
D: Flammable

Question 12

Adv and Dis of pump action spray disp

Answer 12

A: Cheap
D: Only aerosols, not fridges etc

Question 13

Initiation step

Answer 13

CFC broken down into Cl radical and remaining radical

Question 14

2 propagation steps

Answer 14

Cl radical collides with O3》ClO radical and O2
ClO radical collides with O radical》Cl radical and O2

Question 15

Overall reaction of breakdown of Ozone

Answer 15

O3+O》2O2

Question 16

Natural cause of ozone depletion

Answer 16

Nitrogen oxide radicals created by lightning strikes