Download Year 12 Unit 1b - Moulsham High School

A. Harman - moulsham high school
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a)
Demonstrate understanding of:
of
(i)
Name
The nomenclature and corresponding structural and displayed formulae of straight
chain alkanes and alkenes.
Structural
formula
Displayed formula
Name
Structural
formula
H
H
Methane
H C H
CH4
Ethane
Propane
Ethene
H H
H
Propene
C3 H 6
H
H H H
H
C4 H 8
H H H
H C C C C H
C4H10
H H H H
H
H H
H H
C C C C H
H
H H H
H
H H H H
Butane
H
C C C H
H H
Butene
H
C C
H
H C C C H
C3 H 8
C 2H 4
H
H C C H
C 2H 6
Displayed formula
formula
Pentene
C5H10
H H
H C C C C C H
H H H H H
H H H H H
Pentane
H C C C C C H
C5H12
H H H H H
(ii)
The nomenclature and corresponding structural and displayed formulae for:
• primary alcohols
H
R
C
H
•
The OH group is attached to a carbon which is attached to only
one other carbon (or no carbons) eg. Methanol, ethanol
OH
secondary alcohols
H
R
C
R'
OH
A. Harman - moulsham high school
The OH group is attached to a carbon which is attached to two
other carbons
2
tertiary alcohols
R''
R
C
R'
•
aldehydes
Name
Methanal
OH
The OH group is attached to a carbon which is attached to three
other carbons
Structural formula
CH2O
Displayed formula
H
C O
H
Ethanal
CH3CHO
H
O
H C C
H
H
•
ketones.
Name
Structural formula
Displayed formula
Methanone and ethanone cannot exist
Propanone
CH3COCH3
H O H
H C C C H
H
Butanone
CH3COCH2CH3
H
H O H H
H C C C C H
H
H H
(iii)
The following terms as associated with the structure of organic molecules: molecular
formulae; structural formulae,; displayed formulae;; structural isomers; functional
group, homologous
homologous series
(iv)
The following terms as associated with organic reactions: oxidation and reduction,
elimination reactions (when some atoms are removed from an organic molecule)..
b)
Recall the major properties associated with covalent bonding
c)
Interpret the
the physical properties of alcohols as characteristic of covalent compounds
d)
Recall the typical behaviour of alcohols limited to:
A. Harman - moulsham high school
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•
•
•
•
•
•
Combustion – Alcohols are oxidised by combustion to produce carbon dioxide and
water.
solubility in water – The OH bond is polar which causes hydrogen bonding.
treatment with sodium – Reduces the alcohol to the sodium salt eg. Sodium ethoxide
oxidation to carboxylic acids, aldehydes and ketones – 1o alcohols are oxidised to
aldehydes and then to carboxylic acids. 2o alcohols are oxidised to ketones.
results of testing oxidation products with Benedict’s solution – Aldehydes give a
brick red precipitate with Benedict’s. Ketones do not react at all.
Dehydration to alkene – Water is lost from the alcohol to make the alkene with the
help of an aluminium oxide catalyst.
e)
Perform calculations of reacting quantities involving organic compounds and percentage yield.
f)
Evaluate information by extraction from text and the book of data about the properties and
uses of alcohols.
alcohols
A. Harman - moulsham high school
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Topic 2
1.
Draw the displayed formula for methanol.
(1)
2.
Five formulae of alcohols with the same molecular formula, C4H10O, are shown below.
(a)
What is the name given to organic compounds with the same molecular formula, but
different structural formulae?
......................................................................................................................................
(1)
(b)
Which TWO of the formulae, A to E, represent the same alcohol?
......................................................................................................................................
(1)
(c)
Which formula represents a tertiary alcohol?
......................................................................................................................................
(1)
A. Harman - moulsham high school
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(d)
Name alcohol A.
......................................................................................................................................
(1)
(e)
Which TWO of the alcohols, A to E, can be each readily oxidised to a carboxylic acid?
......................................................................................................................................
(2)
(f)
All of the alcohols, A to E, can be dehydrated.
(i)
What is meant by the term dehydrated?
............................................................................................................................
(1)
(ii)
What functional group is formed when an alcohol is dehydrated?
............................................................................................................................
(1)
(iii)
Draw the displayed formula and give the name of the compound formed when
alcohol E is dehydrated.
Displayed formula
Name ......................................................................................................................
(2)
(Total 10 marks)
3.
(a)
Propan-1-ol can be dehydrated to produce propene gas.
(i)
Draw the displayed formula of propan-1-ol.
(1)
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(ii)
One method used to dehydrate propan-1-ol uses a solid catalyst.
Draw a fully labelled diagram of the apparatus used to prepare and collect propene
gas. Name the solid catalyst.
(4)
(b)
Propan-1-ol reacts with sodium to produce an ionic compound and hydrogen gas.
(i)
Name the ionic compound formed.
............................................................................................................................
(1)
(ii)
When carrying out this reaction, a student collected 48 cm3 of hydrogen gas at
room temperature and pressure. Calculate the number of moles of hydrogen
molecules collected.
[Molar volume is 24 000 cm3 mol–1 at room temperature and pressure]
(1)
(c)
Propan-1-ol can be partially oxidised to produce the aldehyde, propanal.
Some alcohols can be oxidised to produce ketones.
(i)
Write the structural formula and give the name of the alcohol that can be oxidised
to produce the ketone, propanone.
Formula ............................................................................................................
Name ................................................................................................................
(2)
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(ii)
Describe what you would expect to see if propanal and propanone were separately
warmed with Benedict’s solution.
Propanal
............................................................................................................................
............................................................................................................................
Propanone
............................................................................................................................
............................................................................................................................
(2)
(Total 11 marks)
4.
(a)
Cyclohexanol and hexan-1-ol are both alcohols containing 6 carbon atoms per molecule.
(i)
Draw the displayed formula of each alcohol.
cyclohexanol
hexan-1-ol
(2)
(ii)
Explain why cyclohexanol and hexan-1-ol are not isomers.
..........................................................................................................................
..........................................................................................................................
(1)
(iii)
State whether each of the two alcohols is a primary, secondary or tertiary alcohol.
Cyclohexanol ....................................................................................................
Hexan-1-ol ........................................................................................................
(2)
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(iv)
Hexan-1-ol was heated gently with a mixture of potassium dichromate and
sulphuric acid. The product of the reaction was distilled off as it formed.
Give the structural formula of the product and name it.
Name .................................................................................................................
(2)
(v)
The reaction in (iv) was repeated using cyclohexanol. The products which were
distilled off from each of the two alcohols contain different functional groups.
State a test to distinguish between these functional groups and give the result in
each case.
Test ..................................................................................................................
..........................................................................................................................
Result with the product from hexan-1-ol .........................................................
..........................................................................................................................
Result with the product from cyclohexanol .....................................................
..........................................................................................................................
(3)
(b)
Cyclohexanol can be converted to cyclohexene.
(i)
What type of reaction is this?
............................................................................................................................
(1)
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(ii)
Draw a fully labelled diagram of the laboratory apparatus, including the chemicals,
which you would use to convert cyclohexanol into cyclohexene and collect the
liquid cyclohexene which forms.
(4)
(iii)
Describe how you would obtain a dry sample of cyclohexene from the liquid
collected.
..........................................................................................................................
..........................................................................................................................
..........................................................................................................................
(2)
(Total 17 marks)
5.
The following reaction scheme shows some of the reactions of butan-2-ol.
(a)
Why is butan-2-ol classified as a secondary alcohol?
.......................................................................................................................................
.......................................................................................................................................
.......................................................................................................................................
(1)
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(b)
Compound A can be prepared from butan-2-ol by passing its vapour over a heated solid,
X.
(i)
Give the name of the organic compound A.
................................................................................................................................
(1)
(ii)
Name the solid X.
................................................................................................................................
(1)
(iii)
What type of reaction is taking place?
................................................................................................................................
(1)
(iv)
Draw a labelled diagram of the apparatus you would use to prepare and collect gas
A from butan-2-ol.
(4)
(v)
Give the structural formula of another possible product of this reaction.
(1)
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(c)
(i)
State TWO observations which could be made while butan-2-ol is reacting with
sodium.
Observation 1 .........................................................................................................
................................................................................................................................
Observation 2 .........................................................................................................
................................................................................................................................
(2)
(ii)
Give the molecular formula of B.
................................................................................................................................
(1)
(d)
(i)
Give the structural formula and the name of compound C.
Structural formula ..................................................................................................
Name ......................................................................................................................
(2)
(ii)
Describe the appearance of the mixture after compound C is boiled with Benedict’s
solution.
................................................................................................................................
................................................................................................................................
(1)
(e)
Butan-2-ol can be used to clean plastic materials, such as CDs and DVDs.
Suggest ONE precaution which should be taken when using butan-2-ol in this way.
.......................................................................................................................................
.......................................................................................................................................
.......................................................................................................................................
(1)
(Total 16 marks)
6.
Properties of some organic compounds containing three carbon atoms per molecule are
summarised on the following chart.
C3 H 6
Reaction 1
C3 H 7 OH
Reaction 2
C3 H 6 O
Y
Na
X
A. Harman - moulsham high school
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(a)
(i)
What type of reaction is Reaction 1?
..........................................................................................................................
(1)
(ii)
Name or give the formula for a suitable reagent for carrying out Reaction 1.
..........................................................................................................................
(1)
(iii)
What type of hydrocarbon is the compound C3H6?
..........................................................................................................................
(1)
(b)
(i)
Write the structural formula for the ionic solid X which may be isolated from the
reaction involving sodium, showing the ionic charges clearly.
..........................................................................................................................
(2)
(ii)
What gas is produced at the same time as X?
..........................................................................................................................
(1)
(c)
(i)
What type of reaction is Reaction 2?
..........................................................................................................................
(1)
(ii)
Name or give chemical formulae for suitable reagents for carrying out
this conversion.
.......................................... mixed with ............................................................
(2)
(d)
The compound Y is found not to react with Benedict’s solution. Draw displayed
formulae for Y and for the alcohol from which it is made.
Y, C3H6O
alcohol, C3H7OH
(4)
(Total 13 marks)
A. Harman - moulsham high school
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7.
(a)
Draw a displayed formula for 2–methylpropan–1–ol.
(2)
(b)
Is this a primary, secondary or tertiary alcohol?
....................................................................................................................................
(1)
(Total 3 marks)
8.
An alcohol, X, has the molecular formula C4H10O.
(a)
X reacts with sodium, forming bubbles of a colourless gas.
Write a balanced equation for the reaction.
(2)
(b)
When X is heated under reflux with a mixture of sodium dichromate(VI) solution and
concentrated sulphuric acid, a green solution forms.
(i)
Give the formula of the ion responsible for the green colour of the solution.
...........................................................................................................................
(1)
(ii)
Draw a labelled diagram of the apparatus used to reflux the mixture.
(3)
A. Harman - moulsham high school
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(iii)
A colourless organic liquid, Y, is distilled from the green solution.
This liquid will not neutralise sodium carbonate solution, and it will not react with
Benedict’s solution.
Draw the displayed formula of Y and state its name.
Displayed formula
Name ....................................................................................................................
(2)
(iv)
Deduce the structural formula of X.
...........................................................................................................................
(1)
(c)
Dehydration of X produces a mixture of products.
(i)
Name a reagent which could be used to dehydrate X.
...........................................................................................................................
(1)
(ii)
Draw displayed formulae of TWO of the possible dehydration products.
(2)
A. Harman - moulsham high school
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(d)
An isomer of X
•
does not react with a mixture of sodium dichromate(VI) solution and concentrated
sulphuric acid
•
reacts with sodium
•
can be dehydrated.
Draw the displayed formula and state the name of this isomer of X.
Displayed formula
Name .................................................................................................................................
(2)
(Total 14 marks)
9.
This question is about the secondary alcohol, X, which has the molecular formula C4H10O.
(a)
Draw the displayed formula of this secondary alcohol, X. Give its systematic name.
Name ...........................................................................................................................
(3)
A. Harman - moulsham high school
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(b)
(i)
Draw the structural formula of Y, a primary alcohol, which is an isomer of X.
(1)
(ii)
If X and Y are heated with sodium dichromate and sulphuric acid, products with
different functional groups are formed. Give the names of the products which could
be formed.
Oxidation product of X .....................................................................................
Oxidation products of Y .....................................................................................
.....................................................................................
(3)
(c)
(i)
Draw a fully labelled diagram of the laboratory apparatus to show how the alcohol
Y could be fully oxidised.
(3)
(ii)
How would you separate the organic product of this reaction from the resulting
mixture?
...........................................................................................................................
(1)
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(d)
(i)
The secondary alcohol, X, can be dehydrated. Draw the structural formulae and
give the names of TWO possible alkenes which could be formed.
(3)
(ii)
If either of the alkenes is shaken with acidified potassium manganate(VII), what
colour change would you see?
From .................................................... to ..........................................................
(1)
(iii)
What other reagent could you use to show that the products of the dehydration of X
are alkenes?
............................................................................................................................
(1)
(Total 16 marks)
10.
This question is about some of the isomers with the molecular formula C4H8O.
(a)
Draw the structural formula of the isomer(A) which is a ketone.
A
(1)
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(b)
Draw the displayed formula and give the name of an isomer(B) which would turn
Benedict’s solution from blue to red on warming.
Displayed formula of B
Name of B......................................................
(2)
(c)
Draw the structural formula of an isomer(C) which is both an alkene and an alcohol.
C
(1)
(d)
Draw the structural formulae for two isomers(D and E) which are cyclic alcohols.
D
E
(2)
(e)
(i)
Which of your isomers(A to E) would react with sodium to give off hydrogen?
.................................................................................................................
(1)
(ii)
For ONE of the isomers you listed in (e)(i), write a balanced equation for its
reaction with sodium. Show the charges on the ionic product.
(2)
(f)
Which one of the isomers(A to E) will decolourize bromine water?
....................................................................................................................................
(1)
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(g)
State TWO reagents that can be used to dehydrate your alcohols D and E. Suggest a
structural formula for either of the organic products.
....................................................................................................................................
....................................................................................................................................
(3)
(Total 13 marks)
11.(a) Draw the displayed formula of a tertiary alcohol containing four carbon atoms.
(2)
(b)
Give the structural formula of the alkene that would be obtained by dehydrating your
tertiary alcohol.
(1)
(Total 3 marks)
12.
Propene, C3H6, can be made by the dehydration of propan–1–ol.
(a)
Draw a displayed formula for propene.
(1)
(b)
Propan–1–ol can be dehydrated by passing its vapour over a heated catalyst or by heating
it with a dehydrating agent.
(i)
Name a suitable catalyst ....................................................................................
(ii)
Name a suitable dehydrating agent .....................................................................
(2)
(c)
(i)
Name and draw a displayed formula for a secondary alcohol which is an isomer of
propan–1–ol.
Name.................................................................................................................
Displayed formula
(2)
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(ii)
If your laboratory had run out of propan–1–ol, would your isomer in (c)(i) be
equally suitable for making propene?
Justify your answer.
..........................................................................................................................
..........................................................................................................................
..........................................................................................................................
(2)
(Total 7 marks)
13.
The six structures, A to F, represent compounds with the same molecular formula, C6H12O.
H
H
C
C
H
H
H
C
C
C
CH3
H
H
H
C
OH
H
CH 3
C
C
H
H
C2H5
A
B
OH
H
H
H
H
H
H
H
C
C
C
C
C
C
H
H
H
H
H
C
H
O
D
H
H
H
O
H
H
C
C
C
C
C
C
H
H
H
H
H
H
H
H
H
OH H
C
C
C
H
H
CH3
E
(a)
OH
C
H
C
H
F
What is the name given to compounds which have different structural formulae but the
same molecular formula?
……………………………………………………………………………………….
(1)
(b)
Which two of the compounds, A to F, are the same?
……………………………………………………………………………………….
(1)
(c)
What is the name of compound E?
……………………………………………………………………………………….
(2)
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(d)
(i)
Which of the compounds, A to F, could be readily oxidized to a carboxylic acid
containing six carbon atoms?
…………………..…………………………………………………………….
(2)
(ii)
Which TWO reagents would be used and what conditions are required?
Reagents ………………………………………………………………………
…………………..…………………………………………………………….
Conditions …………………………………………………………………….
(3)
(Total 9 marks)
14.
This question is about butan–1–ol, C4H9OH, some of whose reactions are shown below:
C 4 H 9 ONa
C 3 H 7 CHO
B
A
Reaction 1
Reaction 2
C 4 H 9 OH
Reaction 4
C4 H 8
D
(a)
Reaction 3
C 3 H 7 CO 2 H
C
Draw a displayed formula for butan–1–ol.
(1)
(b)
Name the reactant which must be added to butan–1–ol to bring about Reaction 1.
....................................................................................................................................
(1)
(c)
In Reaction 2 the same reagents can be used as in Reaction 3 but under
different conditions.
(ii)
What is the general name given to this type of reaction?
..........................................................................................................................
(1)
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(ii)
Name the two reagents needed to bring about both these reactions.
..........................................................................................................................
..........................................................................................................................
(2)
(iii)
What conditions would be used to bring about each reaction?
Reaction 2 .......................................................................................................
Reaction 3 .......................................................................................................
(2)
(d)
How could you distinguish between pure samples of substances B and C in your
school laboratory?
Give a different test for each substance and describe the expected result.
Test for substance B ..................................................................................................
....................................................................................................................................
Result .........................................................................................................................
....................................................................................................................................
Test for substance C ..................................................................................................
....................................................................................................................................
Result .........................................................................................................................
....................................................................................................................................
(4)
(e)
Which reaction will result in the formation of an ionic organic product?
....................................................................................................................................
(1)
(f)
(i)
Draw a labelled diagram to show how you would carry out Reaction 4 in the
laboratory to collect a sample of substance D.
(4)
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(ii)
What would you expect to see when substance D is shaken with an acidified
solution of potassium manganate (VII)?
Colour at the start .............................................................................................
Colour at the end ..............................................................................................
(2)
(iii)
Write a balanced equation, including state symbols, for the complete combustion of
substance D in air.
..........................................................................................................................
(3)
(Total 21 marks)
15.
What is the name of the technique which involves boiling a liquid in a flask fitted with a vertical
water–cooled condenser?
..............................................................................................................................................
(1)
16.
Methanol may be oxidized catalytically using the following apparatus:
Glass rod
Platinum wire
preheated until
red–hot
Methanol
When placed in position, the wire continues to glow and the pungent odour of methanal
is noticed.
(a)
Draw the displayed formula for the pungent–smelling product, methanal.
(1)
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(b)
(i)
What is the oxidizing agent in this reaction?
..........................................................................................................................
(1)
(ii)
What can be deduced from the fact that the wire continues to glow?
..........................................................................................................................
(1)
(c)
The reaction can be carried out by an alternative method.
(i)
What oxidising mixture might be used in an alternative method?
............................................... mixed with ........................................................
(2)
(ii)
When an alternative method is used a possible problem is that the methanal might
be oxidized further to methanoic acid.
Suggest TWO ways of minimizing this problem.
A .......................................................................................................................
B .......................................................................................................................
(2)
(d)
What colour change is expected when methanal is warmed with Benedict’s solution (with
added sodium hydroxide if necessary)?
From ...................................................... to ..............................................................
(2)
(Total 9 marks)
17.
Some reactions of butan–2–ol are illustrated on the following reaction scheme.
X
oxidizing
agent
CH 3 CH 2 CHOHCH 3
Na
Y
butan–2–ol
conc. H3 PO4
Z
(a)
Write the name and structural formula for the organic product X.
Name ............................................... Formula .............................................................
(2)
(b)
Name a suitable oxidizing agent for obtaining X and name a suitable acid to use with it.
Oxidizing agent ............................................................................................................
Acid .............................................................................................................................
(2)
(c)
What would you expect to see if a sample of X was warmed with Benedict’s solution,
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which is initially blue?
....................................................................................................................................
....................................................................................................................................
(1)
(d)
Give a formula for the ionic product Y showing clearly its ionic charges.
(2)
(e)
Z is a mixture of isomeric products. Give structural formulae for two of them.
(2)
(f)
What type of organic reaction is the production of Z from butan–2–ol?
....................................................................................................................................
(1)
(Total 10 marks)
18.
What is the name of the compound represented by the following displayed formula
H
H
H
H
C
C
C
C
H
H
O
H
H
..............................................................................................................................................
(1)
19.
Give the names and structural formulae of the main organic products formed when
(a)
ethanol is treated with sodium
Name .........................................................................................................................
Structural formula
(2)
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(b)
cyclohexanol is oxidized with sodium dichromatic(VI) and sulphuric acid
Name .........................................................................................................................
Structural formula
(2)
(Total 4 marks)
20.
In the preparation of cyclohexanone (molar mass = 98 g mol–1) from cyclohexanol (molar mass
= 100 g mol–1), 2.0 g of cyclohexanol was reacted and 1.2 g of cyclohexanone was obtained.
Calculate the percentage yield, quoting your answer to 2 significant figures.
(2)
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a)
Demonstrate understanding of the terms:
terms
•
•
•
•
b)
standard conditions – A temperature of 298 K and a pressure of 100 kPa
standard enthalpy changes of formation – The enthalpy change when one mole of a
compound is formed from its elements under standard conditions; both elements and
compound are in their standard states
standard enthalpy changes
changes of reaction – The enthalpy change when amounts of reactants, as
shown in the reaction equation, react together under standard conditions to give products in
their standard states.
Hess’s Law – The total enthalpy change for a chemical reaction is independent of the route by
which the reaction takes place, provided initial and final conditions are the same.
Plan investigations for determining enthalpy changes and justify the procedures involved.
In these experiments you need to:
1. Use a polystyrene cup to act as an insulating vessel..
2. Add known amounts of reactants and stir
3. Measure temperature change using at thermometer that reads to at least 0.2oC accuracy.
4. Calculate energy transfer using:
Energy transfer = mc∆T (joules)
c)
Calculate enthalpy changes from experimental data, with the energy changes given in joules.
Energy transfer = mc∆T (joules)
d)
Select appropriate data to calculate enthalpy changes of reaction using Hess’s Law
eg. Methane is formed from the reaction of carbon and hydrogen.
C(s) + 2H2(g)
What is
CH4(g)
for this reaction?
are
In order to determine this value, we need to make use of reactions for which the values of
known. The reactions must be such that when they are combined, they give the desired reaction.
Reaction A
C(s) + O2(g)
CO2(g)
= –393.5 kJ mol-1
And Reaction B
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2H2(g) + O2(g)
2H2O(l)
= –571.6 kJ mol-1
If we add A and B, we get
C(s) + 2H2(g) + 2O2(g)
CO2(g) + 2H2O(l)
Reaction C
CH4(g) + 2O2(g)
CO2(g) + 2H2O(l)
= –890 kJ mol-1
If we reverse reaction C and then add it to the combination of A and B, we get:
C(s) + 2H2(g) + 2O2(g)
CO2(g) + 2H2O(l)
C(s) + 2H2(g)
CO2(g) + 2H2O(l)
CH4(g) + 2O2(g)
CH4(g)
These can be shown on an energy level diagram:
This shows methane being formed and then oxidised on the right hand side.
Carbon and hydrogen are oxidised separately on the left hand side.
The products are the same in
each case.
= -393.5 -571.6 + 890 (since we reversed Reaction C, the value
of is now positive).
= -75.1 kJ mol-1
A. Harman - moulsham high school
29
Topic 5
21. Use the Hess cycle and the data, at 298 K, to calculate the standard enthalpy change of formation
of chloroethene.
∆H
C2 H 3 Cl(g) +114 O 2 (g)
[C 2 H 3 Cl(g)]
∆ H f [H 2 O(l)]
∆ H f [CO 2 (g)]
c
∆ H c [C 2 H 3 Cl]
= –1264 kj mol –1
= – 286 kj mol –1
= – 394 kj mol –1
2CO 2 (g) + 32 H 2 O(l) + 21 Cl 2 (g)
∆ H f [C 2 H 3 Cl]
2C(graphite) + 32 H 2 (g) + 12 Cl2 (g) + 114 O 2 (g)
(3)
22.
1.308 g of zinc was added to an excess of copper(II) sulphate solution. The heat energy
produced was measured and found to be 4.40 kJ.
Calculate the standard enthalpy change for the reaction, giving its correct sign and units.
Use the Periodic Table as a source of data.
(3)
23.
This question is about zinc and some of its compounds.
Zinc is extracted from zinc sulphide by a process which begins with the roasting of the sulphide
ore in air.
2ZnS(s) + 3O2(g)
2ZnO(s) + 2SO2(g)
Values for ∆Hf at 298 K for the compounds in the equation are given below.
∆H f [ZnS(s)] = –200 kJ mol–1
∆H f [ZnO(s)] = –348 kJ mol–1
∆H f [SO2(g)] = –297 kJ mol–1
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(a)
(i)
Explain fully what is meant by ∆H f [ZnS(s)] at 298 K.
..……………………………………………………………………………….
..……………………………………………………………………………….
(2)
(ii)
Calculate ∆Ht for this reaction giving the sign and appropriate units in your answer.
(2)
(iii)
Is the reaction exothermic or endothermic?
..……………………………………………………………………………….
(1)
(b)
(i)
What environmental pollution problem could arise from this process?
..……………………………………………………………………………….
(1)
(ii)
What type of substance could be used to react with and so remove this pollutant?
..……………………………………………………………………………….
(1)
(c)
By considering your answers to part (a)(iii) and (b) suggest TWO things a manufacturer
might do to make the production of zinc more profitable.
Explain how each of your suggestions would make the process more economic.
……………………………………………………………………………………….
……………………………………………………………………………………….
……………………………………………………………………………………….
……………………………………………………………………………………….
(3)
(d)
(i)
Suggest a reaction by which zinc could be obtained from zinc oxide.
Justify your answer by reference to the reactivity series.
..……………………………………………………………………………….
..……………………………………………………………………………….
..……………………………………………………………………………….
(2)
(ii)
What type of reaction is this?
..……………………………………………………………………………….
(1)
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(e)
Zinc sulphate can be obtained from the solution formed by dissolving zinc oxide in dilute
sulphuric acid.
(i)
Write a balanced equation, including state symbols, for the reaction between zinc
oxide and dilute sulphuric acid.
(2)
(ii)
Describe how you would obtain dry crystals of hydrated zinc sulphate,
ZnSO4.7H2O, from the solution.
..……………………………………………………………………………….
..……………………………………………………………………………….
..……………………………………………………………………………….
..……………………………………………………………………………….
..……………………………………………………………………………….
..……………………………………………………………………………….
(3)
(f)
(i)
What is the mass of 1 mole of zinc sulphate crystals, ZnSO4.7H2O?
Use the Periodic Table as a source of data.
(2)
(ii)
5.0 g of the crude zinc sulphide ore was converted into exactly 5.0 g of pure
hydrated zinc sulphate crystals.
Calculate the percentage purity of the zinc sulphide ore, assuming 100% conversion
in the reactions.
(3)
(Total 23 marks)
24.
Sodium hydrogencarbonate, NaHCO3, decomposes on heating. The decomposition products are
sodium carbonate, carbon dioxide and water. The equation for the reaction is
2NaHCO3(s) → Na2CO3(s) + CO2(g) + H2O(l)
The standard enthalpy changes of formation at 298 K of the four compounds are listed below
∆Hf /kJ mol–1
A. Harman - moulsham high school
NaHCO3(s)
–951
Na2CO3(s)
–1131
CO2(g)
–394
H2O(l)
–286
32
(a)
Complete the following Hess cycle by filling in the empty box.
2NaHCO3(S)
∆H2
Na2HCO3(S) + CO2(g) + H2O(I)
∆H1
∆H3
(2)
(b)
Use your completed cycle to calculate the standard enthalpy change (in kJ) accompanying
the thermal decomposition of 2 moles of sodium hydrogencarbonate.
Remember to include the appropriate sign in your answer.
(2)
(c)
–
The hydrogencarbonate ion, HCO3 , can behave either as an acid or as a base, using the
Brøsted–Lowry definitions.
Write down the formula of the entity (ion or molecule) produced in each case.
(i)
–
When acting as an acid, HCO3 becomes ……………………………………
(ii)
–
When acting as a base, HCO3 becomes ……………………………………..
(2)
(d)
A clean nichrome wire was moistened with concentrated hydrochloric acid, then dipped
into a sample of sodium hydrogencarbonate and held in a non–luminous Bunsen flame.
What colour would the flame be?
….……………………………………………………………………………………
(1)
(e)
Samples of sodium hydrogencarbonate to be used in baking powder must be of high
purity.
How could examination of the emission spectrum of a sample be used to check that it did
not contain a significant quantity of potassium?
….……………………………………………………………………………………
….……………………………………………………………………………………
….……………………………………………………………………………………
….……………………………………………………………………………………
(1)
(Total 8 marks)
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25.
An excess of zinc powder was added to 20.0 cm3 of a solution of copper(II) sulphate of
concentration 0.500 mol dm–3. The temperature increased by 26.3 °C.
(a)
How many moles of copper(II) sulphate were used in this experiment?
(1)
(b)
Calculate the enthalpy change, ∆H, in kJ mol–1 for this reaction given that:
energy change =
specific
heat capacity
× mass of
solution
× temperature
change
/J
/J g−1 K−1
/g
/K
Assume that the mass of solution is 20.0 g and the specific heat capacity of the solution
is 4.18 J g–1K–1.
(2)
(Total 5 marks)
26.
This question is about a self-heating can of coffee.
The bottom of the can has a compartment containing copper(II) nitrate solution. When a button
on the bottom of the can is pressed, magnesium powder is released into the compartment where
it reacts with the copper(II) nitrate solution.
(a)
(i)
Write an ionic equation for the reaction between magnesium powder and copper(II)
ions. Include state symbols, but omit any spectator ions.
(2)
A. Harman - moulsham high school
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(ii)
Show how the standard enthalpy change for this reaction could be calculated from
the standard enthalpies of formation of copper(II) ions and magnesium ions. You
should include a Hess cycle in your answer.
(3)
(b)
The can contains 150 g of a solution of coffee in water.
The temperature of the solution needs to increase by 60 °C to produce a hot drink.
(i)
Calculate the energy change needed to produce a temperature increase of 60 °C in
the coffee, using the relationship
Energy change = 4.2 × mass of solution × temperature change.
Remember to include a unit in your answer.
(2)
(ii)
The standard enthalpy change for this reaction is –530 kJ mol–1.
Calculate the number of moles of reactants needed to produce the energy change in
(i).
(1)
A. Harman - moulsham high school
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(iii)
A solution of copper(II) nitrate of concentration 8.0 mol dm–3 is used.
Use your answer to (ii) to calculate the volume, in cm3, of copper(II) nitrate
solution needed.
Your answer should be given to two significant figures.
(1)
(c)
Suggest TWO reasons why the temperature of the coffee may not increase by as much as
60 °C.
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
(2)
(Total 11 marks)
27.
A reaction of ammonium dichromate(VI) is shown by the following equation.
(NH4)2Cr2O7(s) heat
→ N2(g) + 4H2O(g) + Cr2O3(s)
(a)
What type of reaction is this?
......................................................................................................................................
(1)
(b)
The enthalpy change for this reaction can be calculated from standard enthalpy changes of
formation.
(i)
State fully what is meant by the standard enthalpy change of formation, ∆Hfο,
of a compound.
...............................................................................................................................
...............................................................................................................................
...............................................................................................................................
...............................................................................................................................
(3)
A. Harman - moulsham high school
36
(ii)
Complete the Hess cycle for the reaction so that you can calculate the enthalpy
change of the reaction from standard enthalpy changes of formation.
(3)
(iii)
What is the value of ∆Hfο[N2(g)]? ......................................................................
(1)
(iv)
Calculate ∆Hοr for the reaction using the following data. Remember to include a
sign and units in your answer.
–1810 kJ mol–1
∆Hfο[(NH4)2Cr2O7(s)]
=
∆Hfο[H2O(g)]
=
–242 kJ mol–1
∆Hfο[Cr2O3(s)]
=
–1140 kJ mol–1
(3)
A. Harman - moulsham high school
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(c)
In this reaction, water vapour is formed which condenses to liquid water on cooling.
Is this reaction H2O(g) → H2O(l) exothermic or endothermic?
Justify your answer.
......................................................................................................................................
......................................................................................................................................
......................................................................................................................................
......................................................................................................................................
(2)
(Total 13 marks)
28.
When solutions of potassium carbonate and calcium chloride are mixed together, the following
reaction takes place
CaCl2(aq) + K2CO3(aq) → CaCO3(s) + 2KCl(aq)
(a)
Re-write the above equation as an ionic equation. Include state symbols, but omit any
spectator ions.
(2)
(b)
An experiment was carried out to measure the enthalpy change for this reaction. 50 cm3 of
a 1.00 mol dm–3 solution of potassium carbonate was added to 50 cm3 of a 1.00 mol dm–3
solution of calcium chloride. The temperature fell by 1.5 °C.
(i)
Calculate the energy taken in from the surroundings using the relationship
energy =
/J
mass of
solution
/g
× specific heat capacity × temperature
of solution
change
–1
–1
/J g °C
/°C
You may assume that
•
1.0 cm3 of solution has a mass of 1.0 g.
•
The specific heat capacity of the solution is 4.2 J g–1 °C–1.
Energy taken in = .................... J
(1)
(ii)
How many moles of calcium chloride are used in this experiment?
A. Harman - moulsham high school
38
(1)
(iii)
Calculate the enthalpy change for the reaction, giving your answer to two
significant figures. Include a sign and units in your answer.
(2)
(iv)
Which measurement is likely to have caused the major source of error in this
experiment? Explain your answer.
................................................................................................................................
................................................................................................................................
................................................................................................................................
................................................................................................................................
(1)
(v)
What apparatus should be used to contain the reaction mixture during this
experiment?
................................................................................................................................
(1)
(c)
If the experiment in (b) was repeated, but using only 25 cm3 of each solution, predict what
the fall in temperature would be.
.......................................................................................................................................
(1)
(Total 9 marks)
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