Chemical Kinetics and Energetics (12)1, 6 One suggestion for the
reduction of greenhouse gas emissions from coal-fired power
stations is to separate the CO2 from the flue gases and pump it
into the sea bed, where it can dissolve in water under
pressure.
()
()
() During this process, hydrogen bonds are formed between CO2
and H2O moledules. What will be the signs of H and S for this
equilibrium for the forward reaction? HS A-- B-+ C+- D++ (12)1, 12
Lead is the final product formed by a series of changes in which
the rate-determining step is the radioactive decayofuranium-238.
This radioactive decay is afirst-order reaction with a half-life of
4.5 x 109 years. How long would it take for a rock sample,
originally lead-free, to contain a molar proportion of uranium to
lead of 1:3? A.1.5 x 109 years B.2.25 x 109 years C.9.0 x 109 years
D.13.5 x 109 years (12)1, 13 The decomposition of hydrogen peroxide
in aqueous solution is a first order process. If 10% of the
hydrogen peroxide in a solution of concentration 0.1moldm-3
decomposes in 5
minutesatacertaintemperature,whatpercentageofthehydrogenperoxideinasolutionof
concentration 0.2moldm-3 would decompose in 5 minutes at the same
temperature? A.5% B.10% C.19% D.20% (12)1, 14 The uncatalysed
reaction between SO2 and O2 is slow.
ThereactionisspeededupinthepresenceofthehomogeneouscatalystNO,which
participates as follows.
Whichreactionpathwaydiagramismostappropriatefordescribingtheenthalpychanges
occurringduringthecatalysedreaction?Ineachcasethereactionpathwayforthe
uncatalysed reaction is shown as a dashed line. (11)1, 5 The
standard enthalpy change of combustion of but-1-ene, C4H8(g), is x
kJmol-1. The standard enthalpy change of the reaction
()
() is y kJmol-1. What is the standard enthalpy change of
combustion of ethene, C2H4(g)? A.
B.
C.
D.
(11)1, 6 The table shows the charge and radius of each of six
ions. IonJ+L+M2+X-Y-Z2- Radius /nm0.140.180.150.140.180.15 The
ionic solids JX, LY and MZ are of the same lattice type. What is
the correct order of their lattice energies, placing the most
exothermic first? A.JX, MZ, LY B.LY, MZ, JX C.MZ, JX, LY D.MZ, LY,
JX (11)1, 7 At temperatures below 13C, shiny, ductile metallic tin,
known as white tin, changes slowly into a grey powder which is
brittle. Data for each form of tin are given in the table. Hf
/kJmol-1S /JK-1mol-1 White051.4 Grey-2.0944.1 What is the
expression for G, in Jmol-1, for the formation of grey tin from
white tin at 12C? A.G = -2.09 285(-7.3) B.G = -2.09 12(+7.3) C.G =
-2090 12(+7.3) D.G = -2090 -285(-7.3) (11)1, 12 The reaction
between NO2 and SO2 is a key stage in the formation of acid
rain.
()
() ()
() The initial rate of this reaction was measured for different
concentrations of reactants and the following results obtained.
[NO2] /moldm-3[SO2] /moldm-3Relative rate 0.0050.0051.00
0.0060.0061.44 0.0080.0061.92 Which row gives the correct orders of
reaction with respect to the two reactants? Order with respect to
[NO2] Order with respect to [SO2] A10 B11 C20 D21 (11)1, 13 The
rate of the decomposition of the diazonium cation,
can be followed by measuring the time taken for the same volume
of nitrogen to be produced from a range of diazonium cation
concentrations.
Tofindtheorderofthereactionwithrespecttothediazoniumcation,whichwouldbethe
most suitable graph to plot using the data? A.[C6H5N2+] against
time B.[C6H5N2+] against 1/time C.Volume N2 against time D.Volume
N2 against 1/time (11)1, 34 The kinetics of the zero order reaction
were investigated under different conditions. The table shows pairs
of quantities that were plotted as graphs. Which pairs gave the
following graph? y-axisx-axis 1RateTime 2Rate constantTime 3Rate
constantTemperature (10)1, 8 Which class of reaction always has an
endothermic enthalpy change? A.Atomisation B.Combustion C.Formation
D.Solution (10)1, 9 The diagram shows the reaction pathway diagram
for an uncatalysed reaction. The reaction is then catalysed. What
are the changes in the rate constant and the reaction pathway
diagram? (10)1, 10 When steam condenses, 44kJmol-1 of heat enthalpy
is evolved. What is the entropy change when 54g of steam condenses
at 100C? A.-354 JK-1mol-1 B.-118 JK-1mol-1 C.118 JK-1mol-1 D.354
JK-1mol-1 (10)1, 33
Solutesdissolveinsolventstoformsolutions.Ifasemi-permeablemembrane,thatallows
solventmoleculestopassthroughit,isplacedbetweenapuresolventandasolution
containinga solute in that solvent, puresolventonly willgo through
the membrane into the solution. This process is called osmosis. In
which processes will S be positive? 1.Dissolving the solute in a
solvent 2.The evaporation of the solvent from the solution 3.The
passage of the solvent through a semi-permeable membrane during
osmosis (10)1, 34 Hydrogen reacts with gaseous bromine to form
hydrogen bromide,
()
() () and with gaseous iodine to form hydrogen iodide.
()
() () For the first reaction, the rate equation is
[
][
]
[
]
[] For the second reaction, the rate equation is [
][
] What can be deduced from this information only? 1.For the
hydrogen/bromine reaction, the formation of HBr slows down therate
of the forward reaction. 2.Only the hydrogen/iodine reaction could
be a single step reaction. 3.The mechanism of the hydrogen/bromine
reaction involves free radicals. (12)2, 2
Fossilfuelswhicharefoundindepositsbeneaththegroundhavebeenformedfromplants
and animals that lived up to 300 million years ago.
Whenfossilfuelsareburnedininternalcombustionengines,CO2andH2Oarethemain
products, with NO and SO2 also being formed. a)[3]
i.Whichclassofcompound,presentinfossilfuels,producesCO2andH2Oon
combustion? ii.Briefly explain how NO is formed in an internal
combustion engine.
iii.Suggestwhichclassofcompound,originallypresentinthelivingmatterthat
producedthefossilfuel,containedthesulphurthatproducesSO2on
combustion.
Mostofthesulphurpresentinfossilfuelsisremovedatoilrefineries.Itisusedtoproduce
SO2 which is converted, in the Contact process, into SO3 which is
used for the manufacture of sulfuric acid. The Contact process
involves the oxidation of SO2 using a vanadium(V) oxide
catalyst.
()
()
()---------- reaction 1 b)[4] i.At 298K, Hf(SO2) = -297 kJmol-1
and Hf(SO3) = -396kJmol-1. Use these data to calculate H for
reaction 1. State the units. ii.For reaction 1, S = -93.5JK-1mol-1
at 298K. Use this value and your answer to (i) to calculate G for
reaction 1 at 298K. For any reaction, G and the equilibrium
constant, Kc, are related according to the equation
. c)[7] i.Use this equation to calculate a value of Kc for the
oxidation of SO2 at 298K. ii.Suggest what is the significance of
the magnitude of our answer in (i). iii.Suggest why SO2 and SO3 is
formed when sulphur is heated in air.
iv.Useyouranswerto(iii)tosuggestwhyacatalystisusedindustriallyinthe
Contact process. Explain your answer. (12)3, 3 a)When heated, the
carbonates of the Group II elements can lose carbon dioxide.
()()
()
Undertheinfluenceofthemetalcation,thecarbonateionisthoughttobreakupas
follows. O-O-OM2+M2+O2-+CO2 The nitrates of the Group II elements
also decompose on heating. [3] i.Write an equation for the
decomposition of Mg(NO3)2.
ii.StateandexplainthetrendobservedinthethermalstabilityoftheGroupII
nitrates.
b)Dinitrogenpentoxide,N2O5,existsascovalentmoleculesO2N-O-NO2inthegas
phase,butastheionic[NO2+NO3-]inthesolidorinsolution.N2O5hasbeen
suggested as a possible intermediate in the thermal decomposition
of Group II nitrates M(NO3)2. [7] i.Using this information, and
that provided in (a), suggest a mechanism for the formation of N2O5
from a Group II nitrate, M(NO3)2. N2O5 decomposes on heating in a
first order reaction to give NO2 and O2. The mechanism of this
thermal decomposition is thought to involve three steps.
ThereisaninitialhomolyticbreakingofanN-ObondtogiveNO2and NO3
radicals. ThisisfollowedbythedimerizationoftheNO3radicaltogiveN2O6,
which contains a O-O- peroxide bond. The third step involves the
dissociation of this dimer via further N-O bond cleavage to form
the products. ii.Write a balanced equation for the thermal
decomposition of N2O5.
iii.Usetheinformationgivenabovetodrawoutthefullmechanismforthe
thermal decomposition of N2O5. You are advised to use structural
formulae for allspecies,suchas NO OO H2NOO H2
forN2O5,sothatitisclearwhich bonds are broken and which are formed.
Indicate any unpaired electrons by a dot ().
iv.Suggestwhichofthestepsyouhavedrawnisthesloweststep.Explainyour
reasoning.
c)WhenbenzeneisaddedtoasolutionofN2O5inCCl4,anexcellentyieldof
nitrobenzene is obtained in the absence of any added catalyst. [3]
i.Suggest the other product formed during this reaction.
ii.Suggestamechanismforthisreaction,showingallchargesandusingcurly
arrows to show the movements of electron pairs. The following table
lists some Hf values. CompoundHf /kJmol-1 NO2(g)+33.2 N2O5(g)+5.0
The enthalpy change for the dissociation of N2O5(g) is given below.
Reaction 1:
()
()
(), H = +92.5kJmol-1 d)Use the data above to calculate [3] i.Hf
of NO3(g), ii.H for reaction 2. Reaction 2:
()
()
()
e)Byconsideringtheentropyandenthalpychangesduringreaction1andreaction2,
suggest how the standard Gibbs free energy change of the two
reactions will compare in sign and in magnitude. Hence predict
which reaction will be the more spontaneous. Explainyour reasoning.
[4] (11)3, 4 a)Briefly describe what is meant by the secondary,
tertiary and quaternary structures of proteins. [6]
b)Oncetheprimarystructuresofthepolypeptidechainsofhaemoglobinhavebeen
formedfromtheirconstituentaminoacids,andinthepresenceofhaemgroups,the
chains spontaneously coalesce into a haemoglobin molecule. By
considering the chemical interactions involved at each step,
suggest what the signs of G, H and S would be for the overall
process. Explain your reasoning. [3] (10)2, 3
Nitrogenmonoxide,NO,isaby-productofthecombustionofhydrocarbonfuelsininternal
combustion engines. a)NO is considered to be involved in the
formation of acid rain. State one other undesirable consequence of
the presence of NO in the atmosphere. [1] Nitrogen monoxide is
readily converted into nitrogen dioxide. ()
()
() In order to determine the rate equation for this reaction, an
investigation wascarried out at a constant temperature and with the
same partial pressure of oxygen,
, for each experiment.The following results were obtained.
Initial rate /Nm-2s-116.247.278.8124172
/Nm-20.300.500.660.820.95 (
)
/N2m-40.090.250.440.670.90
b)Todeterminetheorderofreactionwithrespectto
,usethesedatatoplota suitable graph. [3] c)What is the order of
reaction with respect to
? Explain your answer. [2] d)The partial pressure of oxygen was
halved and a new series of experiments carried out at the same
temperature. When a similar graph was plotted, the gradient at each
point was half that obtained from the first graph. What is the
order of reaction with respect to
? Explain your answer. [2] e)[2] i.Construct the rate equation
for the reaction between NO and O2. ii.What are the units of the
rate constant for this reaction? (10)2, 4
DataconcerningtheelementsofGroupIIofthePeriodicTable,at298K,aregiveninthe
table. Further data may be found in the Data Booklet. No
calculation is required. MgCaSrBa Hhydration of M2+
/kJmol-1-1980-1650-1480-1365 Shydration of M2+
/Jmol-1K-1-293-238-222-188 Ghydration of M2+
/kJmol-1-1895-1582-1415-1310 Solubility of sulphate/mol per 100g
water1.8 x 10-14.7 x 10-37.1 x 10-59.4 x 10-7 a)When a salt such as
a Group II sulphate dissolves in water, the lattice energy must be
overcome. [2]
i.HowwillthemagnitudeofthelatticeenergyofGroupIIsulfateschange from
MgSO4 to BaSO4? ii.Suggest a reason for this trend.
b)Whenthesulfatehasdissolved,theanionsandcationsareeachsurroundedbya
numberofwatermolecules.Theformationofthesehydratedionsisanexothermic
process. [4]
i.Drawsimplediagramstoshowhowawatermoleculecanbeattachedtoa
magnesium cation, and to a sulfate anion. Label each diagram to
show the type of interaction involved. ii.Suggest why Hhydration of
M2+ becomes less negative from Mg2+ to Ba2+.
