Home Practice Examples Unit 2 part 1
1. Consider the following equations :
A. 2CO
+
02
B.
2C02
+ 702
C. C8H18
+ 121/202
3CO2 + 4H20
8CO2
D. 2NO
+
2CO
N2
E. N2
+
O2
2NO
+ 4C0
+ 9H20
+ 2CO2
Using only the letters for the equations, list those reactions most likely
to occur:
a) in the engine of a car
b) in a catalytic converter.
2. a) State why a car engine has a spark plug.
b) What is auto-ignition?
c) Auto-ignition is easily recognised because it causes a noise.
What name do we give to this phenomenon?
d) Give two reasons why auto-ignition is undesirable.
e) What compounds were added to petrol (up to the mid 1990s) to
reduce the risk of auto-ignition?
f) What is the present day solution to this problem?
3. Fossil fuels are finite. Methane is the main constituent of one
fossil fuel.
a) Name the fossil fuel.
b) State briefly how methane can be made from a renewable
source.
4. Read the following statements about naphtha and then
answer the questions which follow.
A
B
C
D
E
F
It consists of different shaped molecules with the molecular
formula C7H16.
It is a mixture of hydrocarbons with boiling points within a
certain range.
It can be used to make good quality petrol by having the
shape of its molecules altered.
It is separated from crude oil by a process that depends on
boiling points
It is frequently used, unaltered, as a fuel.
It is less volatile than diesel.
a) Identify by number the statements that are true about naphtha.
b) Which numbered statement refers to
(i) fractional distillation (ii) isomers (iii) reforming?
5.
There is likely to be a different between petrol bought in summer
and petrol bought in winter.
a) State the likely difference, in terms of chain length of the
molecules.
b) Explain the reason for the difference.
c) State one undesirable effect for each of using:
(i)
summer petrol on a very cold winter day.
(ii)
winter petrol on a very hot summer day
d) Suggest an experiment you could carry out in the lab to
distinguish between a sample of summer petrol and a sample of
winter petrol. (Remember – no naked flames can be used.)
6. During an average year about 50 people in Britain die from poisoning
caused by carbon monoxide fumes from faulty heating appliances.
a) State the conditions under which a burning fuel will produce
carbon monoxide.
b) It has been stated that sooty stains near, or above the appliance
is a warning sign that carbon monoxide may be produced. Explain
the connection between production of soot and the production of
carbon monoxide.
7.
8.
Ethanol can be made from glucose.
a) Name the process involved
b) Name the source of the catalyst.
c) Name the type of catalyst involved.
d) State why we do not use ethanol as a source of liquid
fuel in Scotland.
e) Sugar extracted from sugar cane has already provided ethanol to
be blended with conventional petrol in Brazil. State one reason
why sugar cane is likely to be a source of fuel well into the 21st
century.
f) (i) Name another alkanol being considered as an alternative fuel.
(ii) State two disadvantages in using this other alkanol as a fuel.
g) Show (i) the molecular and (ii) the structural formulae of ethanol
and this other alkanol.
C7H16
+ 02
CO2
+
H2O
This unbalanced equation is shown in a third year pupil’s notes to
represent the burning of petrol in a car engine.
a) Balance the above equation for the reaction.
b) Name three other gases that are commonly present in car exhaust,
and state the source of each gas.
c) Write a balanced equation for the burning of hydrogen.
d) Compare the products of the equations in the answers to 8. a) and
8. c) Suggest one environmental advantage as a fuel in place of
petrol.
9. Reforming is an important process in the petroleum industry.
a) Name molecules A. and B.
b) Molecules B can be classified as an aromatic hydrocarbon. Classify
the hydrocarbon molecules A and C.
c) Molecule D is a branched chain hydrocarbon. Draw a possible
structure for this molecule.
10. Here are the boiling points of hydrocarbons.
Alkane
Butane
Pentane
Heptane
Octane
Boiling POINT /ºC.
-1
36
98
126
Cycloalkane
Boiling Point /ºC.
Cyclobutane
12
Cyclopentane
49
Clyloheptane
118
Clclooctane
148
a) (i) How do the boiling points of hydrocarbons change as
the molecular size increases?
(ii) Explain why the boiling points change in this way.
b) (i) How do the boiling of alkanes compare with those of
cycloalkanes?
(ii)
Explain your answer to b) in terms of the forces of
attraction between the molecules and the ability of the
molecules to make close contact.
c) Use the data in the table to predict the boiling points of:
(i) hexane
(ii) cyclohexane.
d) Use your data booklet to note the actual boiling point for each of
these compounds.
(i) hexane
(ii) cyclohexane.
11. (i) Name these molecules:
a) CH3C(CH3)2CH2CH2CH3
b) CH3CH2CCCH2CH2CH3
c)
d)
e)
f) CH2=CHCH2CH3
(ii) Identify the isomers by letter.
12. a) Give the general formulae for the:
(i) alkanes (ii) alkenes (iii) alkynes (iv) cycloalkanes (v) cycloalkenes
b) Your answer to a) should help you to identify a homologous
series in each case which will provide isomers for:
(i) cycloalkaes
(ii) cycloalkanes.
c) Using only molecules with four carbon atoms draw the structural
formulae of examples to justify your answers to both parts of b) above.
d) Explain with reference to the alkanes, why the alkenes and
cycloalkanes have the same general formula.
13. a) For each of the following molecules draw
(i)
shortened structural formulae (ii) full structural formulae
A. 4,4-dimethylpent-2-yne
B. cyclohexane
C. 4-ethyl-2,2-dimethylhexane D. hexa-1,3,5-triene
b) Which of the above molecules, A to D, are:
(i) saturated
(ii) unsaturated (iii) hydrocarbons
(iv) straight chain
(viii) alkynes
(vi) cyclic
(vii) alkanes
14. (a) Hydrocarbons can be sub-divided into several groups, mostly
____________ series (which have general formulae).
(b) Complete the following classification of hydrocarbons:
15.
a) Write chemical equations, using molecular formulae, for:
(i) reaction A
(ii) reaction B
b) What name can be applied to both reactions?
c) Name the organic chemicals in your equations in a) (i) and (ii) which are
saturated?
16. Saturated hydrocarbons are commonly used as fuels.
Unsaturated hydrocarbons are generally unsuitable for use as
fuels.
a) Write a balanced equation for the complete combustion of hexane.
b) (i) Describe the test (and of course the result) for unsaturated
hydrocarbons.
(ii) Represent this test as an equation using hexane as your example.
(iii) Write the colours of the chemicals below each formula in b) (ii).
c) State whether alkanes or alkenes are more reactive. Give a reason.
17. Ethene reacts with hydrogen chloride to form one product.
a) Name this type of reaction.
b) (i) Use equations to show that propene can form two isomeric products
in a similar reaction.
Write the names of two products under their formulae.
18.
Substance A
Substance B
A pupil found that both these molecules decolourise bromine solution
immediately when well mixed. However she claimed that, using the bromine
solution, she could tell which was which.
Describe and explain a method that she could use.
19.
CH3C=CCH2CH3 can react with bromine in a two stage reaction.
a) To which homologous series does the hydrocarbon belong?
b) Name the kind of reaction described.
c) Show the full structural formula and name the product at each
stage.
20.
Ethyne can react with hydrogen chloride gas in two stages to form two
isomeric molecules B and C. In the flow diagram below give the structural
formulae for molecules A, B, and C, and name each of these substances.
21. Ethanol has been made for centuries by fermentation. In the last 50 years
ethanol has also become a by-product of the petroleum industry.
a)
b)
State the reason for using this new synthetic route.
Complete the flow diagram for the preparation carried out in the
petroleum industry, writing the type of reaction in the process box, and
the reaction conditions above and below the arrow.
c)
Rewrite the reaction as an equation using structural formulae.
d)
Propanol can be made by a reaction similar to the synthesis of ethanol
in b). Two isomers of propanol can be formed in this reaction. Write an
equation for the reaction using structural formulae to show how the
two isomers are formed. Name both isomers.
22.
Identify the molecule(s) which:
a) are primary alkanols.
b) Can be made by hydration of but-2-ene.
c) Will form but-1-ene when passed over hot aluminium oxide.
d) Will form 2-methylprop-1-ene on dehydration.
23.
a) Identify the process(es).
(i) hydrogenation
(ii) dehydrogenation
(ii) hydration
(iv) dehydration.
b) Identify the process which
(i) occurs in a catalytic cracker
(ii) is used to supplement the alcohol made by fermentation.
(iii) Uses Ni powder as a catalyst
(iv) Uses phosphoric acid as the catalyst in industry
(v) Uses hot Al2O3 as a catalyst in the laboratory experiment.
24. a) Draw the full structural formula and shortened structural
formula for butanal.
b) Name and write the shortened structural formula for:
c) Name and draw the full structural formula for CH3CH2COCH3.
d) Name and write the shortened structural formula for:
25. Which of the following statements are true of the alkanals?
a) Which of the following statements are true of the alkanals?
b) All of the members can be represented by the same general formula.
c) The chemical properties of all the members are similar.
d) The physical properties of all the members are similar.
e) The longer the chain the more van der Waals’ forces will form
between the molecules and so the greater the viscosity.
f) Each member differs from its neighbours in the series by a –CH2group only
26. a) Explain why CH3CH2COCH3 can be called butanone and
not butan-2-one.
b) Explain why there is not a compound with the name
butan-1-one.
27.
Copy each of the above structures then circle and label the following
functional groups each time they occur:
Carboxyl, hydroxyl; (state whether primary, secondary or tertiary);
carbon to carbon double bond.
28. Alkanols can be oxidised in two stages.
a) Name a suitable oxidising agent.
b) State the colour changes you would see during this experiment.
c) Name the class of compound formed at each stage of the reaction.
29.
Identify a substance which:
a)
b)
c)
d)
e)
can be oxidised to an aldehyde.
Is a ketone
Is a carboxylic acid.
Cannot be oxidised by acidified dichromate solution
Can be formed by oxidation of B.
30. The following reaction sequence was noted:
a) State, with reasons, whether Reactions 1 and 2 are oxidations or
reductions.
b) Suggest likely identities for molecules A, B and C.
31.
Identify the substance(s) which
a) is an alcohol but cannot be oxidised by passing over hot copper (II)
oxide.
b) React with tertiary alcohol.
c) Will form a ketone on oxidation.
Problem Solving Questions
1.
CL2
C4H10
A
Light
NaOH
C4H9C1
B
C4H10O
C
Compound C is an alcohol which does not react with acidified potassium
dichromate solution.
a)
Explain why compound C does not react with acidified potassium
dichromate.
From this information, identify the structure for compound C and
hence compounds B and A.
Name compounds A to C.
b)
c)
2.
Br2
C4H10
A
NaOH
C4H9Br
Light
B
H+
C4H10O
C
MnO4-
C4H8O
D
Compound D is stable to oxidation.
a)
b)
c)
d)
3.
C4H10
A
To which class of compounds does D belong?
Hence, identify the type of alcohol which compound C is.
Identify the only possible structures for compounds D, C, B and A.
Name compounds A to E.
Br2
NaOH
H+
H+
C4H9Br
C4H10O
C4H8O
C4H8O2
2Light
B
C
MnO4D
Cr2O7
E
a) Starting with compound E, work backwards through the reaction scheme
to identify the homologous series to which each compound belongs.
b) Identify the structures of all the compounds, from E to A.
c) Name compounds A to E.
4.
5.
Repeat question 3 but give an alternative isomeric set of structures for
these compounds.
A hydrocarbon A, C8H8 reacts with bromine water forming compound B,
C8H8Br2, which does not react further with bromine water.
a) What type of reaction is this?
b) What do the formulae for A and B indicate about these compounds.
c) Assign suitable structures to A and B.
d) Name compound A and give an industrial use for this compound.
6.
Pentane reacts as shown in the above reaction scheme. Compounds B and E
are isomeric alcohols. Compound C does not react with Benedict’s solution
while compound F does.
a) explain the difference in behaviour of compounds C and F with
Benedict’s solution.
b) Assign structures to all of the compounds, A-F.
c) Name compounds A to F.
d) What type of alcohol is compound B.
e) Name a suitable reagent for oxidation of B and another for oxidation of
E.
7.
oxidation
C7H8O
A
Light
oxidation
C7H6O
B
C7H6O2
C
To which classes of compounds to compounds A and C belong?
Identify the structure for compounds A to C.
Name compounds A to C.
8.
Compound B does not react with sodium dichromate solution.
Identify structures for compounds A and B and then name the compounds.
9. Draw and name the isomers of heptane.
10. If you have more time than your know what to do with, draw and name the
isomers of octane!
11. Catalytic dehydration of butan-2-ol in the gas phase produces two products
which are isomers.
12. Butanol (C4H90H) has 4 isomeric structures, all of which are alcohols.
a) Draw and name the isomers.
b) State which of the isomers are primary, secondary or tertiary.
c) The four alcohols are contained, separately, in four bottles marked A, B,
C and D. From the following information decide which bottle contains
which alcohol. State your reasoning briefly at each stage.
i) The contents of A, B and C can readily be oxidised by acidified potassium
dichromate solution, while those of D cannot.
ii) A and B, on complete oxidation by the acidified dichromate, give acids of
formulae C3H7C00H. C does not give an acid.
All four substances can be dehydrated to give alkenes, but
iii)
iv)
A and D can both form the same alkene.
B and C can both form the same alkene, which is an isomer of that
formed by A and D.