2
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Section A
For each question there are four possible answers, A, B, C and D. Choose the one you consider to
be correct.
Use of the Data Booklet may be appropriate for some questions.
11 Which statement about enthalpy changes is correct?
:
A
Enthalpy changes of atomisation are always negative.
B
Enthalpy changes of combustion are always positive.
C
Enthalpy changes of formation are always positive.
D
Enthalpy changes of neutralisation are always negative.
2 2 Beams of charged particles are deflected by an electrical field. The angle of deflection of a
particle is proportional to its charge / mass ratio.
In an experiment protons are deflected by an angle of +15°. In another experiment under identical
conditions 2H– ions are deflected by an angle of Y°.
What is the value of Y?
A
3
–30.0
B
–7.5
C
+7.5
D
+30.0
Rubidium and bromine form ions that are isoelectronic. Each ion has 36 electrons.
Which row is correct?
•
3
4
rubidium radii
bromine
/ bromide radii
A
atomic < ionic
atomic < ionic
B
atomic < ionic
atomic > ionic
C
atomic > ionic
atomic < ionic
D
atomic > ionic
atomic > ionic
In which set do all the molecules have all their atoms arranged in one plane?
A
Al Cl 3, BF3, PH3
B
Al Cl 3, CO2, NH3
C
BF3, C2H4, C3H6
D
C2H4, CO2, H2O
Sof
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The reaction pathway diagram for a chemical reaction is shown.
energy
progress of reaction
Which statement is correct?
A
The activation energy of the forward reaction and the enthalpy change of the backward
reaction have the same sign.
B
The activation energy of the forward reaction is more than twice the enthalpy change of the
backward reaction and opposite in sign.
C
The enthalpy change of the forward reaction and the activation energy of the backward
reaction have the same sign.
D
The enthalpy change of the forward reaction is more than twice the activation energy of the
backward reaction.
Al-Hassan
715 What changes in conditions or molecular properties make it more likely that gases approach ideal
behaviour?
8
A
higher pressure
B
lower temperature
C
more polar molecules
D
weaker intermolecular forces
Ethanol can be oxidised to ethanal by dilute acidified dichromate(VI) ions.
The oxidation reaction equation is C2H5OH → C2H4O + 2H+ + 2e–.
The reduction reaction equation is Cr2O72– + 14H+ + 6e– → 2Cr3+ + 7H2O.
Which equation is correct?
A
Cr2O72– + 8H+ + 3C2H5OH → 2Cr3+ + 7H2O + 3C2H4O
B
Cr2O72– + 12H+ + C2H5OH → 2Cr3+ + 7H2O + C2H4O
C
Cr2O72– + 12H+ + 3C2H5OH → 2Cr3+ + 6H2O + 3C2H4O
D
Cr2O72– + 14H+ + 3C2H5OH → 2Cr3+ + 6H2O + 3C2H4O
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Section B
For each of the questions in this section, one or more of the three numbered statements 1 to 3 may
be correct.
Decide whether each of the statements is or is not correct (you may find it helpful to put a tick against
the statements that you consider to be correct).
The responses A to D should be selected on the basis of
A
B
C
D
1, 2 and 3
are
correct
1 and 2
only are
correct
2 and 3
only are
correct
1 only
is
correct
No other combination of statements is used as a correct response.
Use of the Data Booklet may be appropriate for some questions.
16
31 One mole of sulfuric acid is used to make an aqueous solution. The solution contains H2SO4
molecules, H+ ions, SO42– ions and HSO4– ions.
Which statements are correct?
1
The solution contains 6.02 × 1023 sulfur atoms.
2
The solution contains an exactly equal number of H+ ions and HSO4– ions.
3
One mole of SO42– ions contains two moles of electrons.
32 Which statements are correct?
1
The hydrogen bonds in ice are more regularly arranged than in water.
2
The solidification of water to form ice is exothermic.
3
Pure water is less dense than ice.
33
17 Calcium reacts with water to form calcium hydroxide and hydrogen.
Ca(s) + 2H2O(l) → Ca(OH)2(s) + H2(g)
The standard enthalpy change for this reaction is – 414 kJ mol–1.
What further information is needed in order to calculate the standard enthalpy change of
formation of calcium hydroxide,
Ca(OH)2(s)?
1
for H2O(l)
2
for H2(g)
3
first and second ionisation energies of Ca
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Answer all the questions in the spaces provided.
1
Sulfuric acid is manufactured by the Contact process.
One stage in this process is the conversion of sulfur dioxide into sulfur trioxide in the presence of a
heterogeneous catalyst of vanadium(V) oxide, V2O5.
(a) (i)
=
2 O=S=O(g) + O=O(g)
O
2 O=S=O(g)
H = –196 kJ mol–1
State the effect of a catalyst on a reaction.
Explain how a catalyst causes this effect.
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
....................................................................................................................................... [2]
(ii)
State the meaning of the term heterogeneous as applied to catalysts.
.............................................................................................................................................
.............................................................................................................................................
....................................................................................................................................... [1]
(b) Some bond energies are given.
bond
bond energy / kJ mol–1
S=O (in SO2)
534
O=O
496
Use the data, and the enthalpy change for the conversion of sulfur dioxide into sulfur trioxide,
to calculate a value for the S=O bond energy in SO3.
S=O bond energy in SO3 = .............................. kJ mol–1 [2]
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The Contact process is usually carried out at a temperature of about 400 °C and a pressure just
above atmospheric pressure. Using a higher or lower temperature and pressure would affect both
the rate of production of sulfur trioxide and the yield of sulfur trioxide.
(c) A reaction pathway diagram for both the catalysed and uncatalysed reactions between SO2
and O2 is shown.
A
energy
2SO2 + O2
E
C
D
B
2SO3
progress of reaction
The letters A–E represent energy changes.
Complete the table by stating which letter, A–E, represents the energy change described.
energy change
letter
the energy change for the production of SO3
the activation energy for the production of SO3 in the absence
of a catalyst
the activation energy for the first step in the decomposition of
SO3 in the presence of a catalyst
[3]
AS-NEEDE
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The equation for this stage of the Contact Process is shown.
2SO2(g) + O2(g)
(d) (i)
2SO3(g)
ΔH = –196 kJ mol–1
State and explain the effect of increasing temperature on the rate of production of SO3.
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
....................................................................................................................................... [3]
(ii)
State and explain the effect of increasing temperature on the yield of SO3.
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
....................................................................................................................................... [3]
(e) The SO3 produced is converted to sulfuric acid in two stages. In the first stage the SO3 is
reacted with concentrated sulfuric acid to produce oleum, H2S2O7.
The oleum is then reacted with water to form sulfuric acid.
Suggest an equation for the reaction of oleum, H2S2O7, with water to form sulfuric acid.
.............................................................................................................................................. [1]
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(f) SO2 reacts with water to form sulfurous acid.
Sulfurous acid is a weak Brønsted-Lowry acid, while sulfuric acid is a strong Brønsted-Lowry
acid.
(i)
Complete the ‘dot-and-cross’ diagram to show the bonding in a molecule of SO2. Show
outer electrons only.
[1]
(ii)
State the meaning of the term strong Brønsted-Lowry acid.
.............................................................................................................................................
.............................................................................................................................................
....................................................................................................................................... [2]
(iii)
Write an equation to show the acid-base behaviour of sulfuric acid with water. Include
state symbols.
....................................................................................................................................... [2]
[Total: 20]
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2
The elements in Group 17 of the Periodic Table are called the halogens. They form stable compounds
with both metals and non-metals.
The table gives some data about F2, HCl and CaF2.
(a) (i)
F2
HCl
CaF2
boiling point / K
85
188
2773
relative formula mass
38.0
36.5
78.1
State what is meant by the term relative formula mass.
.............................................................................................................................................
.............................................................................................................................................
....................................................................................................................................... [2]
(ii)
F2 and HCl are both covalent molecules.
Suggest why the boiling point of HCl is higher than that of F2.
.............................................................................................................................................
.............................................................................................................................................
....................................................................................................................................... [2]
(iii)
Explain why CaF2 has a very high boiling point.
.............................................................................................................................................
....................................................................................................................................... [1]
(iv)
CaF2(aq) can be made by the reaction of calcium carbonate with hydrofluoric acid, HF(aq).
Write an equation for this reaction. Include state symbols.
....................................................................................................................................... [2]
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(b) (i)
Complete the electronic configuration of a chloride ion.
1s2 ................................................................................................................................. [1]
(ii)
When Cl 2 is passed over hot iron, FeCl 3 is formed.
However, when I2(g) is passed over hot iron, the following reaction occurs.
Fe(s) + I2(g)
FeI2(s)
State what you would observe during the reaction between Fe and I2. Explain why FeI2(s)
is formed rather than FeI3(s).
observation .........................................................................................................................
.............................................................................................................................................
explanation .........................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
[2]
(iii)
FeI2 is soluble in water.
A student carries out a chemical test to confirm that a solution of FeI2 contains aqueous
iodide ions, I–(aq). The student adds a single reagent and a precipitate forms.
Identify the reagent the student uses. State the colour of the precipitate that forms.
reagent ...............................................................................................................................
colour of precipitate ............................................................................................................
[2]
(iv)
Compounds containing I– are often contaminated by bromide ions, Br –.
Identify a further reagent that the student could use to show that the precipitate formed in
(iii) contained iodide ions.
....................................................................................................................................... [1]
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(c) HOF is the only known molecule that contains only the elements hydrogen, oxygen and fluorine.
(i)
Draw a ‘dot-and-cross’ diagram to represent the bonding in a molecule of HOF.
Show the outer shell electrons only.
[2]
(ii)
HOF can be made by the reaction of F2 with ice at – 40 °C. The reaction is similar to the
reaction of Cl 2 with cold water.
Suggest an equation for the reaction of F2 with ice.
....................................................................................................................................... [1]
(iii)
HOF is an unstable compound and decomposes to form HF and O2.
HOF → HF +
1
2
O2
ΔH = –139 kJ mol–1
Draw a fully labelled reaction pathway diagram on the axes provided to show the
decomposition of HOF into HF and O2.
enthalpy
progress of reaction
[2]
TRISTAR
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(iv)
Pure HF is a colourless liquid at 273 K. The liquid contains HF molecules that have strong
hydrogen bonds between them.
Draw a fully labelled diagram to suggest how a hydrogen bond can form between two HF
molecules.
[3]
(d) Interhalogen compounds, such as BrCl or IF5, contain two or more different halogen atoms
that are covalently bonded.
D is an interhalogen compound that contains only chlorine and fluorine.
At 0 °C and 101 325 Pa, 1 dm3 of D has a mass of 4.13 g.
(i)
Use the general gas equation to calculate the relative molecular mass, Mr, of D.
Mr = ..............................
[3]
(ii)
Use your answer to (i) to determine the molecular formula of D.
If you were unable to calculate the Mr in (i), assume that the Mr is 130.5. This is not the
correct value.
molecular formula of D = ..............................
[1]
[Total: 25]
Tiff
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Trihalomethanes are organic molecules in which three of the hydrogen atoms of methane are
replaced by halogen atoms, for example CHCl 3.
(a) CHCl 3 is a colourless liquid with a high vapour pressure.
(i)
Explain what is meant by high vapour pressure.
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
....................................................................................................................................... [2]
(ii)
An important reaction of CHCl 3(g) is the manufacture of CHCl F2(g), using the following
reversible reaction.
CHCl 3(g) + 2HF(g)
CHCl F2(g) + 2HCl (g)
Use the data to calculate the enthalpy change of reaction, ΔHr , for the formation of
CHCl F2(g) as shown in the equation.
compound
enthalpy change of
formation, ΔHf / kJ mol–1
CHCl 3(g)
–103.2
CHCl F2(g)
– 482.2
HF(g)
–273.3
HCl (g)
–92.3
enthalpy change of reaction, ΔHr = .............................. kJ mol–1 [3]
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(iii)
The reaction in (ii) is carried out using a heterogeneous catalyst.
Explain fully the meaning of the terms heterogeneous and catalyst.
heterogeneous ....................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
catalyst ...............................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
[3]
(b) CHCl F2 was used as an alternative to chlorofluorocarbons (CFCs). CHCl F2 should no longer
be used because it was found to contribute to the enhanced greenhouse effect.
(i)
Give the meaning of the term enhanced greenhouse effect.
.............................................................................................................................................
....................................................................................................................................... [1]
(ii)
Explain how CHCl F2(g) may contribute to this effect.
.............................................................................................................................................
.............................................................................................................................................
....................................................................................................................................... [2]
(iii)
Suggest another environmental problem associated with the use of CHCl F2.
....................................................................................................................................... [1]
_ItD_f&
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(c) CHCl F2 is also used to produce the monomer tetrafluoroethene, C2F4.
This monomer can be used to produce poly(tetrafluoroethene), PTFE.
(i)
State the type of polymerisation that occurs during the production of PTFE.
....................................................................................................................................... [1]
(ii)
(iii)
Draw the repeat unit of PTFE.
[1]
Suggest why PTFE is used as a coating for cooking pans.
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
....................................................................................................................................... [1]
(iv)
Waste disposal can cause litter problems.
State two other difficulties associated with the disposal of PTFE.
1 ..........................................................................................................................................
.............................................................................................................................................
2 ..........................................................................................................................................
.............................................................................................................................................
[2]
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