3.3.3 - halogenoalkanes

Question 1

what does CFCs stand for?

Answer 1

chlorofluorocarbons

Question 2

what are CFCs?

Answer 2

halogenoalkane molecules where all hydrogen atoms have been replaced by chlorine and fluorine atoms

Question 3

what is the ozone layer made from?

Answer 3

(O)3

Question 4

what does the ozone layer do?

Answer 4

absorbs lots of UV radiation from the sun

Question 5

dangers of UV radiation

Answer 5

• sunburn
• skin cancer

Question 6

how is the ozone layer formed?

Answer 6

oxygen molecule is broken down into 2 free radicals by UV radiation

Question 7

first step of ozone layer formation

Answer 7

O2 (+UV) = O. +O.

Question 8

second step of ozone layer formation

Answer 8

O2 + O. = O3

Question 9

CFCs and the ozone layer

Answer 9

CFCs contribute to damaging the ozone layer

Question 10

what is the first step of how CFCs damage the ozone layer?

Answer 10

chlorine radicals are formed e.g.
CCl3F (+UV) = CCl2F +Cl.

Question 11

what is the second step of how CFCs damage the ozone layer

Answer 11

Cl. + O = O2 + ClO.
ClO. + O3 = 2(O2) + Cl.

Question 12

what safer alternatives to CFCs have been made?

Answer 12

• HCFCs (hydrochlorofluorocarbons)
• HFCs (hydrofluorocarbons)

Question 13

what did CFCs mainly used to be used in?

Answer 13

• propellers in aerosols
• fire extinguishers
• coolant gas in fridges

Question 14

properties of CFCs

Answer 14

• pretty unreactive
• non flammable
• non toxic

Question 15

what is a halogenoalkane?

Answer 15

an alkane with at least one halogen atom in place of a hydrogen atom

Question 16

polarity of halogenoalkanes

Answer 16

halogens are generally more electronegative than carbon

Question 17

why are halogen carbon bonds polar?

Answer 17

• halogen is more electronegative so withdraws electron density from carbon atom
• carbon atom has slight positive charge
• halogen atom has slight negative charge