exam questions

Question 1

What is meant by the term radical?

Answer 1

species with an unpaired electron (1)

Question 2

State the conditions necessary to bring about the formation of the chlorine free
radicals from Cl2.

Answer 2

uv (light)/high temperature/min of 400° C/sunlight (1)

Question 3

State the type of bond fission involved in the formation of the chlorine radicals

Answer 3

homolytic (fission) (1)

Question 4

The chlorine radicals react with butane in several steps to produce C4H9Cl.
Write equations for the two propagation steps.

Answer 4

C4H10 + Cl* (1) → C4H9* + HCl (1)
C4H9* + Cl2 (1) → C4H9Cl + Cl*
(1)

Question 5

Ethanol, C2H5OH, is manufactured on a large scale by two methods:
* Fermentation, using yeast, of sugars, such as glucose, C6H12O6.
C6H12O6(aq) → 2C2H5OH(aq) + 2CO2(g)
The ethanol is then distilled off.
* Hydration of ethene, C2H4, with steam in the presence of an acid catalyst.
C2H4(g) + H2O(g) → C2H5OH(g)

Compare the sustainability of these methods of manufacturing ethanol in terms of:
* availability of starting materials and energy requirements;
* atom economy

Answer 5

availability
sugar is renewable because it can be grown (1)
ethane is finite because it is obtained by processing of crude oil (1)

energy:
fermentation: energy is required for distillation/
hydration: energy is required to generate steam (1)

atom economy and waste products:
atom economy for fermentation < atom economy hydration (1)
In fermentation, CO2 is produced in addition to ethanol/ethanol is
not the only product (1)
In hydration, ethanol is the only product/hydration is an addition
reaction (1)
Atom economy of fermentation could be increased by finding a use
CO2 (1)
Atom economy linked to a chemical equation to show that hydration
has 100% atom economy/fermentation has 51% atom economy (1)

Question 6

structural isomers

Answer 6

same molecular formula, different structural formula (1)

Question 7

two ways in which chemists are trying to minimise the damage to the
environment caused by the disposal of polymers.

Answer 7

development of biodegradable polymers
cracking of waste polymers

Question 8

Suggest the general formula for a carboxylic acid.

Answer 8

CnH2nO2

Question 9

Propan-2-ol can be formed by the hydration of an alkene in the presence of a
catalyst.
(i) Suggest a suitable catalyst for this reaction

Answer 9

phosphoric acid

Question 10

What is meant by the term
electrophile?

Answer 10

electron pair of electrons acceptor

Question 11

Suggest why 2-methylbut-2-ene is less soluble in water than either of the structural
isomers formed.

Answer 11

Does not contain OH group(s)

Does not form hydrogen bonds with water ✔

Question 12

What is the general formula of the homologous series that has allyl bromide as a
member?

Answer 12

CnH2n−1Br ✔

Question 13

What does a curly arrow represent in mechanisms?

Answer 13

Movement of an electron pair

Question 14

Explain the increase in boiling points of the cycloalkanes shown in the table

Answer 14

More carbons (in ring)
stronger london forces ✔
More energy needed to break the
intermolecular forces

Question 15

Explain what is meant by the term stereoisomers.

Answer 15

same structural
formula but a different arrangement (of
atoms) in space

Question 16

Why is this step an example of homolytic fission?

Answer 16

one electron from the bond (pair) goes to
each atom / chlorine/radical

Question 17

Describe how a σ-bond forms

Answer 17

Overlap of orbitals directly between the
bonding atoms

Question 18

State one advantage and one disadvantage of using combustion as a method for the
disposal of waste polymer E.

Answer 18

ad-Energy production / (energy) used to produce electricity
dis-Formation of CO2/gases that cause global warming / greenhouse gases