Haloalkanes

Question 1

What elements do haloalkanes contain?

Answer 1

Carbon, hydrogen and at least one halogen.

Question 2

Which order do you list the halogens in the haloalkane?

Answer 2

In alphabetical order.

Question 3

Out of halogen and carbon atoms, which are more electronegative? What does this mean?

Answer 3

The halogen are more electronegative than carbon atoms. The electron pair is therefore closer to the halogen atom than the carbon atom. The carbon-halogen bond is therefore polar.

Question 4

What is the definition of a nucleofile? Give an example

Answer 4

An atom or group of atoms that donate a pair of electrons to form a new covalent bond. An example is hydroxide ions, water molecules and ammonia molecules.

Question 5

What happens in a nucleophilic substitution reaction?

Answer 5

The nucleophile replaces the halogen in a substitution reaction. A new compound is produced containing a different functional group.

Question 6

What is hydrolysis?

Answer 6

A chemical reaction involving water or an aqueous solution of a hydroxide that causes the breaking of a bond in a molecule.

Question 7

What happens in the hydrolysis of a haloalkane? Include a mechanicm diagram in your answer.

Answer 7

The halogen atom is replaced by an -OH group

Question 8

How can you form a haloalkane form an alcohol? What is the other product?

Answer 8

Use a hydrogen halide. A substituation reaction will occur to produce a molecule of water.

Question 9

How can you form a haloalkane from an alkene? What type of reaction is this?

Answer 9

Add a hydrogen halide at room temperature. This is an electrophilic substitution reaction.

Question 10

How can you form a haloalkane from an alkane? Whta type of reaction is this?

Answer 10

Add chlorine under UV light. This is a ncleophilic substitution reaction.

Question 11

What is the bond polarity of carbon to halogen bonds?

Answer 11

C d+ and Cl/Br/F d-

Question 12

Why can H₂O and OH^- act as nucleophiles?

Answer 12

H₂O contains a lone pair of electrons and OH^- has a single lone electron.

Question 13

Acidified silver nitrate is a test for the halides. What colour precipitate would you expect to observe if chlorine is present?

Answer 13

White

Question 14

Acidified silver nitrate is a test for the halides. What colour precipitate would you expect to observe if bromine is present?

Answer 14

Cream

Question 15

Acidified silver nitrate is a test for the halides. What colour precipitate would you expect to observe if iodine is present?

Answer 15

Yellow

Question 16

What is the trend in reactivity as group seven is decended.

Answer 16

The reactivity increases as the group is decended.

Question 17

Fill in the gaps. As Group 7 is _______, the size of the halogen atom _______ so the carbon to halogen bond length _______. This results in the carbon to halogen bond _______ decreasing which means it is _______ to break the bond.

Answer 17

As Group 7 is decended, the size of the halogen atom increases so the carbon to halogen bond length increases. This results in the carbon to halogen bond enthalpy decreasing which means it is easier to break the bond.

Question 18

How does electronegativity change as you go down group 7?

Answer 18

Electronegativity decreases as you go down the group.

Question 19

What conditions are required for the nucleophilic substitution of chloroethane and sodium hydroxide?

Answer 19

Reflux

Question 20

What conditions are required for the nucleophilic substitution of chloroethane and water?

Answer 20

Reflux and an ethanol solvent.

Question 21

What does CFC stand for?

Answer 21

Chlorofluorocarbon

Question 22

Give an example of a CFC.

Answer 22

Trichlorofluoromethane

Question 23

State 4 previous major uses of CFCs.

Answer 23

1) fridges
2) propellant for aerosols
3) air conditioning
4) packaging

Question 24

State three properties of CFCs that make them ideal for their applications to real life.

Answer 24

They are volatile, unreactive and non toxic to humans.

Question 25

Which bond is most likely to be broken in CClF₃?

Answer 25

C-Cl

Question 26

What general name do we give to the highly reactive species formed by homolitic bond fission?

Answer 26

Radicals

Question 27

What health issues can be caused by exposure to UV radiation?

Answer 27

Skin cancer, eye cataracts and a weakened immune system.

Question 28

What happens to ozone (O₃) when it is exposed to UV radiation?

Question 29

What is the Montreal Protocol?

Answer 29

A piece of legislation signed by lots of major countries on the prevention of CFCs

Question 30

Why did ozone levels continue to drop after the introduction of the Montreal Protocol?

Answer 30

Because there were still CFCs and Cl· in the atmosphere.

Question 31

In what year is the ozone predicted to have made a full recovery?

Answer 31

Between 2060 and 2070.

Question 32

Write equations to show the formation and destruction of ozone in the stratosphere.

Answer 32

O₂→2O•

O• + O₂ → O₃

O₃ → O• + O₂

Question 33

How are Cl• formed from CFCs? Use CCl₃F in your equation

Answer 33

CCl₃F → CCl₂F + Cl•

Question 34

How does Cl• react with an O₃ molecule?

Answer 34

Cl•

Question 35

Give the reaction between Nitrogen and Oxygen to give NO•

Why do these reactions require high temperatures to take place?

Answer 35

N₂ + O₂ → 2NO•

Because they have high bond enthalpies.

Question 36

Which peak on a mass spectrometry print out is the base peak? What does this mean?

Answer 36

The highest peak which is the most likely to form.

Question 37

Which peak on a mass spectrometry print out is the molecular ion peak?

Answer 37

The peak that is the furthest to the right.

Question 38

True or false? Only the negative ions are detected by the mass spectrometer.

Answer 38

False. Only positive ions are detected in the mass spectrometer.