chapter 15

Question 1

how do you name the haloalkanes

Answer 1

• they are compounds containing halogen atoms
• parent chain + prefix
• fluoro = fluorine
• chloro = chlorine
• bromo = bromine
• iodo = iodine

Question 2

explain the reactivity of the haloalkanes

Answer 2

• they have a carbon-halogen bond in their molecule
• halogen atoms are more electronegative than the carbon atoms
• their charge can attract a nucleophile

Question 3

what is a nucleophile

Answer 3

• they are negative ions
• they are electron pair donators

Question 4

explain a nucleophilic reactions

Answer 4

• primary haloalkanes undergo nucleophilic substitution reactions
• the halogen atom is replaced with an -oh group to form an alcohol during a hydrolysis reaction

Question 5

hydrolysis and carbon-halogen bond strength

Answer 5

• the rate of haloalkanes depends upon the strength of the carbon-halogen bond
• iodoalkanes react the fastest because the bond is the weakest
• fluoroalkanes will react the slowest because the bond is he strongest

Question 6

the ozone layer

Answer 6

• absorbs the biologically damaging high energy UV radiation
• exposure to UV-B causes sun burn and long term affects such as skin cancer and genetic damage

Question 7

what are some uses of the haloalkanes

Answer 7

• solvents for cleaning
• dry cleaning solvents
• polymers
• flame retardants
• refrigerants

Question 8

explain the ozone layer

Answer 8

• its continually being broken down and reformed
• in a steady state
• the high energy UV radiation breaks oxygen into radicals and then a steady state is formed
• human activity is increasing the reverse reaction meaning it is no longer in a steady state

Question 9

what are CFCs

Answer 9

• chlorofluorocarbons
• strength of the carbon halogen bond is very strong meaning that they are very stable
• chemically inert, non-toxic, low flammability
• low boiling points and can be compressed into liquids

Question 10

explain the chlorine radical cycle

Answer 10

• initiation step makes chlorine radicals, this wont stop until the chlorine reaches the ionosphere
• propagation creates a chain reaction and the chlorine radicals catalyse the rate of the forwards reaction, this means that the chlorine radical is always regenerated

Question 11

give one advantage and one disadvantage of HCFCs

Answer 11

• break down quicker than CFCs
• will break down in the troposphere
• the hydrogen and carbon bonds will break first
• if it gets to the stratosphere, it will still produce the chlorine radicals

Question 12

give an advantage and a disadvantage of HFCs

Answer 12

• contain no chlorine
• doesn’t catalyse the breakdown of the ozone layer
• very expensive to manufacture

Question 13

give an advantage and a disadvantage of hydrocarbons

Answer 13

• propellants in aerosols
• flammable

Question 14

give an advantage and a disadvantage of pump action spray dispensers

Answer 14

• cheap
• cant be used for anything else

Question 15

what is the Montreal protocol

Answer 15

• to introduce steps for the complete removal of CFCs