IB Questionbank Chemistry11.Which statements describe the action
of a catalyst?I.It does not alter the H for a reaction.II.It
increases the Ea for the reaction.III.It alters the mechanism
(pathway) of a reaction.A.I and II onlyB.I and III onlyC.II and III
onlyD.I, II and III(Total 1 mark) 2.Consider the reaction between
gaseous iodine and gaseous hydrogen.I2(g) + H2(g) 2HI(g)HO = 9
kJWhy do some collisions between iodine and hydrogen not result in
the formation of the product?A.The I2 and H2 molecules do not have
sufficient energy.B.The system is in equilibrium.C.The temperature
of the system is too high.D.The activation energy for this reaction
is very low.(Total 1 mark)3.Curve X on the graph below shows the
volume of oxygen formed during the catalytic decomposition of a 1.0
mol dm3 solution of hydrogen peroxide.2H2O2(aq) O2(g) +
2H2O(l)Which change would produce the curve Y?A.Adding
waterB.Adding some 0.1 mol dm3 hydrogen peroxide solutionC.Using a
different catalystD.Lowering the temperature(Total 1 mark)4.Bromine
and nitrogen(II) oxide react according to the following
equation.Br2(g) + 2NO(g) 2NOBr(g)Which rate equation is consistent
with the experimental data?[Br2] / mol dm3[NO] / mol dm3Rate / mol
dm3 s10.100.101.0 1060.200.104.0 1060.200.404.0 106A.rate = k[Br2]2
[NO]B.rate = k[Br2] [NO]2C.rate = k[Br2]2D.rate = k[NO]2(Total 1
mark) 5.Which step is the rate-determining step of a reaction?A.The
step with the lowest activation energyB.The final stepC.The step
with the highest activation energyD.The first step(Total 1
mark)6.Consider the following graph of ln k against (temperature in
Kelvin) for the second order decomposition of N2O into N2 and O.N2O
N2 + O K1 (a)State how the rate constant, k varies with
temperature,
T.............................................................................................................................................................................................................................................................................(1)(b)Determine
the activation energy, Ea, for this
reaction.....................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................(3)
(c)The rate expression for this reaction is rate = k [N2O]2 and the
rate constant is0.244 dm3 mol1 s1 at 750 C.A sample of N2O of
concentration 0.200 mol dm3 is allowed to decompose. Calculate the
rate when 10 % of the N2O has
reacted.........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................(2)(Total
6 marks)7.At 25 C, 200 cm3 of 1.0 mol dm3 nitric acid is added to
5.0 g of magnesium powder. If the experiment is repeated using the
same mass of magnesium powder, which conditions will result in the
same initial reaction rate?Volume of HNO3 / cm3Concentration ofHNO3
/ mol dm3Temperature /
CA.2002.025B.2001.050C.1002.025D.1001.025(Total 1 mark) 8.Factors
that affect the rate of a chemical reaction include particle size,
concentration of reactants and the temperature of the
reaction.(i)Define the term rate of a chemical
reaction.............................................................................................................................................................................................................................................................................(1)
(ii)List the three characteristic properties of reactant particles
which affect the rate of reaction as described by the collision
theory.....................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................(3)(Total
4 marks)9.On the axes below sketch two Maxwell-Boltzmann energy
distribution curves for the same sample of gas, one at a
temperature T and another at a higher temperature . Label both
axes. Explain why raising the temperature increases the rate of a
chemical
reaction.................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................(Total
5 marks) 10.Sodium carbonate and hydrochloric acid react according
to the equation below.Na2CO3(s) + 2HCl(aq) CO2(g) + 2NaCl(aq) +
H2O(l)Which conditions will produce the fastest initial rate with
2.0 g of powdered sodium carbonate?A.100 cm3 of 1.0 mol dm3
hydrochloric acid at 323 KB.50 cm3 of 2.0 mol dm3 hydrochloric acid
at 323 KC.100 cm3 of 1.0 mol dm3 hydrochloric acid at 348 KD.50 cm3
of 2.0 mol dm3 hydrochloric acid at 348 K(Total 1 mark) 11.The rate
information below was obtained for the following reaction at a
constant temperature.2NO2(g) + F2(g) 2NO2F(g)[NO2] / mol dm3[F2] /
mol dm3Rate / mol dm3 s12.0 1031.0 1024.0 1044.0 1031.0 1028.0
1044.0 1032.0 1021.6 103What are the orders of the reaction with
respect to NO2 and F2?A.NO2 is first order and F2 is second
orderB.NO2 is second order and F2 is first orderC.NO2 is first
order and F2 is first orderD.NO2 is second order and F2 is second
order(Total 1 mark) 12.Consider the following reaction.2NO(g) +
2H2(g) N2(g) + 2H2O(g)A proposed reaction mechanism is:NO(g) +
NO(g) N2O2(g)fastN2O2(g) + H2(g) N2O(g) + H2O(g)slowN2O(g) + H2(g)
N2(g) + H2O(g)fastWhat is the rate expression?A.rate = k[H2]
[NO]2B.rate = k[N2O2] [H2]C.rate = k[NO]2 [H2]2D.rate = k[NO]2
[N2O2]2 [H2](Total 1 mark)13.Hydrogen and nitrogen(II) oxide react
according to the following equation.2H2(g) + 2NO(g) N2(g) +
2H2O(g)At time = t seconds, the rate of the reaction israte =
k[H2(g)][NO(g)]2 (i)Explain precisely what the square brackets
around nitrogen(II) oxide, [NO(g)], represent in this
context.............................................................................................................................................................................................................................................................................(1)
(ii)Deduce the units for the rate constant
k.............................................................................................................................................................................................................................................................................(1)(Total
2 marks) 14.Under which conditions will the reaction between 1.0 g
calcium carbonate and excess hydrochloric acid be the fastest?
Assume that all reactions are carried out at the same
temperature.A.One large piece of calcium carbonate and 2 mol dm3
hydrochloric acidB.One large piece of calcium carbonate and 1 mol
dm3 hydrochloric acidC.Powdered calcium carbonate and 2 mol dm3
hydrochloric acidD.Powdered calcium carbonate and 1 mol dm3
hydrochloric acid(Total 1 mark)15.Powdered manganese(IV) oxide,
MnO2(s), increases the rate of the decomposition reaction of
hydrogen peroxide, H2O2(aq). Which statements about MnO2 are
correct?I.The rate is independent of the particle size of
MnO2.II.MnO2 provides an alternative reaction pathway for the
decomposition with a lower activation energy.III.All the MnO2 is
present after the decomposition of the hydrogen peroxide is
complete.A.I and II onlyB.I and III onlyC.II and III onlyD.I, II
and III(Total 1 mark) 16.The Haber process uses an iron catalyst to
convert hydrogen gas, H2(g), and nitrogen gas, N2(g), to ammonia
gas, NH3(g).3H2(g) + N2(g) 2NH3(g)Which statements are correct for
this equilibrium system?I.The iron catalyst increases the rates of
the forward and reverse reactions equally.II.The iron catalyst does
not affect the value of the equilibrium constant, Kc.III.The iron
catalyst increases the yield of ammonia gas, NH3(g).A.I and II
onlyB.I and III onlyC.II and III onlyD.I, II and III(Total 1
mark)17.Alex and Hannah were asked to investigate the kinetics
involved in the iodination of propanone.They were given the
following equation by their teacher.CH3COCH3(aq) + I2(aq)
CH2ICOCH3(aq) + HI(aq)Alexs hypothesis was that the rate will be
affected by changing the concentrations of the propanone and the
iodine, as the reaction can happen without a catalyst. Hannahs
hypothesis was that as the catalyst is involved in the reaction,
the concentrations of the propanone, iodine and the hydrogen ions
will all affect the rate.They carried out several experiments
varying the concentration of one of the reactants or the catalyst
whilst keeping other concentrations and conditions the same. Their
results are shown graphically below. (a)Discuss whether either
Alexs or Hannahs hypothesis is
correct.........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................(2)
(b)Explain why the reaction rate will increase with increasing
temperature.........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................(2)(c)(i)This
reaction uses a catalyst. Sketch and annotate the Maxwell-Boltzmann
energy distribution curve for a reaction with and without a
catalyst on labelled axes below.(3) (ii)Describe how a catalyst
works.......................................................................................................................................................................................................................................................(1)(Total
8 marks) 18.Which experimental procedure could be used to determine
the rate of reaction for the reaction between a solution of cobalt
chloride, CoCl2(aq), and concentrated hydrochloric acid,
HCl(aq)?Co(H2O)62+(aq) + 4Cl(aq) CoCl42(aq) + 6H2O(l)A.Measure the
change in pH in a given timeB.Measure the change in mass in a given
timeC.Use a colorimeter to measure the change in colour in a given
timeD.Measure the change in volume of the solution in a given
time(Total 1 mark)19.Sodium thiosulfate solution, Na2S2O3(aq), and
hydrochloric acid, HCl(aq), react spontaneously to produce solid
sulfur, S(s), according to the equation below.S2O32(aq) + 2H+(aq)
S(s) + SO2(aq) + H2O(l)A student experimentally determined the rate
expression to be:rate = k[S2O32(aq)]2Which graph is consistent with
this information?(Total 1 mark)20.Alex and Hannah were asked to
investigate the kinetics involved in the iodination of
propanone.They were given the following equation by their
teacher.CH3COCH3(aq) + I2(aq) CH2ICOCH3(aq) + HI(aq)Alexs
hypothesis was that the rate will be affected by changing the
concentrations of the propanone and the iodine, as the reaction can
happen without a catalyst. Hannahs hypothesis was that as the
catalyst is involved in the reaction, the concentrations of the
propanone, iodine and the hydrogen ions will all affect the
rate.They carried out several experiments varying the concentration
of one of the reactants or the catalyst while keeping other
concentrations and conditions the same, and obtained the results
below.Composition by volume of mixture / cm3Initial
rateExperiment1.00 mol dm3CH3COCH3(aq)Water1.00 mol dm3H+(aq)5.00
103mol dm3 I2 in KI/ mol dm3 s1110.060.010.020.04.96
106210.050.010.030.05.04 10635.065.010.020.02.47
106410.065.05.020.02.51 106 (a)Explain why they added water to the
mixtures.............................................................................................................................................................................................................................................................................(1)
(b)(i)Deduce the order of reaction for each substance and the rate
expression from the
results.............................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................(2)(ii)Comment
on whether Alexs or Hannahs hypothesis is
correct.......................................................................................................................................................................................................................................................(1)
(c)Using the data from Experiment 1, determine the concentration of
the substances used and the rate constant for the reaction
including its
units.....................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................(3)
(d)(i)This reaction uses a catalyst. Sketch and annotate the
Maxwell-Boltzmann energy distribution curve for a reaction with and
without a catalyst on labelled axes below.(3) (ii)Describe how a
catalyst
works.......................................................................................................................................................................................................................................................(1)(Total
11 marks) 21.(a)The production of ammonia is an important
industrial process.N2(g) + 3H2(g) 2NH3(g) (i)Using the average bond
enthalpy values in Table 10 of the Data Booklet, determine the
standard enthalpy change for this reaction.(3) (ii)The standard
entropy values, S, at 298 K for N2(g), H2(g) and NH3(g) are 193,
131 and 192 JK1 mol1 respectively. Calculate SO for the reaction
and with reference to the equation above, explain the sign of
SO.(4) (iii)Calculate GO for the reaction at 298 K.(1) (iv)Describe
and explain the effect of increasing temperature on the spontaneity
of the reaction.(2) (b)The reaction used in the production of
ammonia is an equilibrium reaction. Outline the characteristics of
a system at equilibrium.(2) (c)Deduce the equilibrium constant
expression, Kc, for the production of ammonia.(1) (d)(i)0.20 mol of
N2(g) and 0.20 mol of H2(g) were allowed to reach equilibrium in a
1dm3 closed container. At equilibrium the concentration of NH3(g)
was 0.060moldm3. Determine the equilibrium concentrations of N2(g)
and H2(g) and calculate the value of Kc.(3) (ii)Predict and explain
how increasing the temperature will affect the value of
Kc.(2)(e)Describe how increasing the pressure affects the yield of
ammonia.(2) (f)In practice, typical conditions used in the Haber
process are a temperature of 500 C and a pressure of 200
atmospheres. Outline why these conditions are used rather than
those that give the highest yield.(2) (g)A catalyst of iron is used
in the Haber process. State and explain how the catalyst affects Kc
and the position of equilibrium.(3)(Total 25 marks) 22.Which unit
could be used for the rate of a chemical reaction?A.molB.mol
dm3C.mol dm3 s1D.dm3(Total 1 mark)23.Which of the following can
increase the rate of a chemical reaction?I.Increasing the
temperatureII.Adding a catalystIII.Increasing the concentration of
reactantsA.I and II onlyB.I and III onlyC.II and III onlyD.I, II
and III(Total 1 mark) 24.The graph below shows how the volume of
carbon dioxide formed varies with time when a hydrochloric acid
solution is added to excess calcium carbonate in a flask.
(i)Explain the shape of the curve.(3) (ii)Copy the above graph on
your answer sheet and sketch the curve you would obtain if double
the volume of hydrochloric acid solution of half the concentration
as in the example above is used instead, with all other variables
kept constant from the original. Explain why the shape of the curve
is different.(4)(iii)Outline one other way in which the rate of
this reaction can be studied in a school laboratory. Sketch a graph
to illustrate how the selected variable would change with time.(2)
(iv)Define the term activation energy and state one reason why the
reaction between calcium carbonate and hydrochloric acid takes
place at a reasonably fast rate at room temperature.(2)(Total 11
marks) 25.The following data were obtained for the reaction between
gases A and B.ExperimentInitial [A] / mol dm3Initial [B] / mol
dm3Initial rate / mol dm3 min111.0 1031.0 1032.0 10422.0 1031.0
1032.0 10432.0 1032.0 1034.0 104Which relationship represents the
rate expression for the reaction?A.rate = k[B]2B.rate = k[A]2C.rate
= k[A]D.rate = k[B](Total 1 mark)26.Consider the following
reaction.NO2(g) + CO(g) NO(g) + CO2(g)At T < 227 C the rate
expression is rate = k[NO2]2. Which of the following mechanisms is
consistent with this rate expression?A.NO2 + NO2 N2O4fastN2O4 + 2CO
2NO + 2CO2slowB.NO2 + CO NO + CO2slowC.NO2 NO + OslowCO + O
CO2fastD.NO2 + NO2 NO3 + NOslowNO3 + CO NO2 + CO2fast(Total 1
mark)27.A piece of zinc was added to aqueous nitric acid and the
volume of hydrogen gas produced was measured every minute. The
results are plotted on the graph below.Which graph would you expect
if the same mass of powdered zinc was added to nitric acid with the
same concentration?(Total 1 mark)28.Which changes increase the rate
of the reaction below?C4H10(g) + Cl2(g) C4H9Cl(l) +
HCl(g)I.Increase of pressureII.Increase of temperatureIII.Removal
of HCl(g)A.I and II onlyB.I and III onlyC.II and III onlyD.I, II
and III(Total 1 mark) 29.What is the equilibrium constant
expression for the reaction below?2NO2(g) N2O4(g)A.Kc = B.Kc = C.Kc
= D.Kc = (Total 1 mark)30.The formation of nitric acid, HNO3(aq),
from nitrogen dioxide, NO2(g), is exothermic and is a reversible
reaction.4NO2(g) + O2(g) + 2H2O(l) 4HNO3(aq)What is the effect of a
catalyst on this reaction?A.It increases the yield of nitric
acid.B.It increases the rate of the forward reaction only.C.It
increases the equilibrium constant.D.It has no effect on the
equilibrium position.(Total 1 mark) 31.The Haber process enables
the large-scale production of ammonia needed to make
fertilizers.The equation for the Haber process is given below.N2(g)
+ 3H2 2NH3(g)The percentage of ammonia in the equilibrium mixture
varies with temperature. (i)Use the graph to deduce whether the
forward reaction is exothermic or endothermic and explain your
choice.(2) (ii)State and explain the effect of increasing the
pressure on the yield of ammonia.(2)(iii)Explain the effect of
increasing the temperature on the rate of reaction.(2)(Total 6
marks) 32.Consider the following reaction.2P + Q R + SThis reaction
occurs according to the following mechanism.P + Q XslowP + X R +
SfastWhat is the rate expression?A.rate = k[P]B.rate =
k[P][X]C.rate = k[P][Q]D.rate = k[P]2[Q](Total 1 mark) 33.What
happens when the temperature of a reaction increases?A.The
activation energy increases.B.The rate constant increases.C.The
enthalpy change increases.D.The order of the reaction
increases.(Total 1 mark) 34.(a)There are four structural isomers
with the molecular formula C4H9Br. One of these structural isomers
exists as two optical isomers. Draw diagrams to represent the
three-dimensional structures of the two optical isomers.(2)(b)All
the isomers can by hydrolysed with aqueous sodium hydroxide
solution. When the reaction of one of these isomers, X, was
investigated the following kinetic data were
obtained.ExperimentInitial [X] /mol dm3Initial [OH] /mol dm3Initial
rate of reaction /mol dm3 min112.0 1022.0 1024.0 10322.0 1024.0
1024.0 10334.0 1024.0 1028.0 103 (i)Deduce the rate expression for
the reaction.(3) (ii)Determine the value of the rate constant for
the reaction and state its units.(2) (iii)State the name of isomer
X and explain your choice.(2) (iv)State equations for the steps
that take place in the mechanism of this reaction and state which
of the steps is slow and which is fast.(2)(Total 11 marks) 35.What
is the best definition of rate of reaction?A.The time it takes to
use up all the reactantsB.The rate at which all the reactants are
used upC.The time it takes for one of the reactants to be used
upD.The increase in concentration of a product per unit time(Total
1 mark)36.Which factors can affect reaction rate?I.The state of the
reactantsII.The frequency of the collisions between
particlesIII.The average kinetic energy of the particlesA.I and II
onlyB.I and III onlyC.II and III onlyD.I, II and III(Total 1 mark)
37.Equal masses of powdered calcium carbonate were added to
separate solutions of hydrochloric acid. The calcium carbonate was
in excess. The volume of carbon dioxide produced was measured at
regular intervals. Which curves best represent the evolution of
carbon dioxide against time for the acid solutions shown in the
table below.25 cm3 of 2 mol dm3 HCl50 cm3 of 1 mol dm3 HCl25 cm3 of
1 mol dm3 HClA.IIIIIVB.IIVIIIC.IIIIIID.IIIIII(Total 1 mark) 38.This
question refers to the following reaction.X2 + 2Y 2XYThe reaction
occurs in a series of steps.X2 2XslowX + Y XYfastWhat is the
rate-determining step for this reaction mechanism?A.X2 + 2Y 2XYB.X2
+ Y XY + XC.X2 2XD.X + Y XY(Total 1 mark) 39.This question refers
to the following reaction.X2 + 2Y 2XYThe reaction occurs in a
series of steps.X2 2XslowX + Y XYfastWhat is the rate expression
for this reaction?A.rate = k[XY]B.rate = k[X2][Y]2C.rate =
k[X2]D.rate = k[2X](Total 1 mark)40.What is the function of iron in
the Haber process?A.It shifts the position of equilibrium towards
the products.B.It decreases the rate of the reaction.C.It provides
an alternative reaction pathway with a lower activation energy.D.It
reduces the enthalpy change of the reaction.(Total 1 mark)
41.(a)Define the term activation energy,
Ea.............................................................................................................................................................................................................................................................................(1)
(b)State two conditions necessary for a reaction to take place
between two reactant
particles.........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................(2)(c)Sketch
an enthalpy level diagram to describe the effect of a catalyst on
an exothermic reaction.(3)(Total 6 marks) 42.Consider the following
reaction.5Br(aq) + BrO3(aq) + 6H+(aq) 3Br2(aq) + 3H2O(l)The rate
expression for the reaction is found to be:rate = k[Br]
[BrO3][H+]2Which statement is correct?A.The overall order is
12.B.Doubling the concentration of all of the reactants at the same
time would increase the rate of the reaction by a factor of
16.C.The units of the rate constant, k, are mol dm3 s1.D.A change
in concentration of Br or BrO3 does not affect the rate of the
reaction.(Total 1 mark)43.The rate expression for a reaction
is:rate = k [X][Y]Which statement is correct?A.As the temperature
increases the rate constant decreases.B.The rate constant increases
with increased temperature but eventually reaches a constant
value.C.As the temperature increases the rate constant
increases.D.The rate constant is not affected by a change in
temperature.(Total 1 mark) 44.Consider the following reaction
mechanism.Step 1H2O2 + I H2O + IOslowStep 2H2O2 + IO H2O + O2 +
IfastWhich statement correctly identifies the rate-determining step
and the explanation?A.Step 2 because it is the faster stepB.Step 1
because it is the slower stepC.Step 1 because it is the first
stepD.Step 2 because it is the last step(Total 1 mark) 45.(i)Define
the term rate of reaction.(1) (ii)State an equation for the
reaction of magnesium carbonate with dilute hydrochloric
acid.(1)(iii)The rate of this reaction in (ii), can be studied by
measuring the volume of gas collected over a period of time. Sketch
a graph which shows how the volume of gas collected changes with
time.(1) (iv)The experiment is repeated using a sample of
hydrochloric acid with double the volume, but half the
concentration of the original acid. Draw a second line on the graph
you sketched in part (iii) to show the results in this experiment.
Explain why this line is different from the original line.(4)(Total
7 marks) 46.Nitrogen monoxide reacts at 1280 C with hydrogen to
form nitrogen and water.All reactants and products are in the
gaseous phase.(i)The kinetics of the reaction were studied at this
temperature. The table shows the initial rate of reaction for
different concentrations of each reactant.experiment[NO(g)]/mol dm3
103[H2(g)]/mol dm3 103Initial rate/mol dm3 s1
10515.002.001.25210.002.005.00310.004.0010.00Deduce the order of
the reaction with respect to NO and H2, and explain your
reasoning.(4) (ii)Deduce the rate expression for the reaction.(1)
(iii)Determine the value of the rate constant for the reaction from
Experiment 3 and state its units.(2)(Total 7 marks)47.The gas-phase
decomposition of dinitrogen monoxide is considered to occur in two
steps.Step 1: N2O(g) N2(g) + O(g)Step 2: N2O(g) + O(g) N2(g) +
O2(g)The experimental rate expression for this reaction is rate = k
[N2O]. (i)Identify the rate-determining step.(1) (ii)Identify the
intermediate involved in the reaction.(1)(Total 2 marks) 48.The
conversion of CH3NC into CH3CN is an exothermic reaction which can
be represented as follows.CH3NC transition state CH3CNThis reaction
was carried out at different temperatures and a value of the rate
constant, k, was obtained for each temperature. A graph of ln k
against 1/T is shown below.(i)Define the term activation energy,
Ea.(1) (ii)Construct the enthalpy level diagram and label the
activation energy, Ea, the enthalpy change, H, and the position of
the transition state.(3) (iii)Describe qualitatively the
relationship between the rate constant, k, and the temperature,
T.(1) (iv)Calculate the activation energy, Ea, for the reaction,
using Table 1 of the Data Booklet.(4)(Total 9 marks)
49.Hydrochloric acid is reacted with large pieces of calcium
carbonate, the reaction is then repeated using calcium carbonate
powder. How does this change affect the activation energy and the
collision frequency?Activation energyCollision
frequencyA.increasesincreasesB.stays
constantincreasesC.increasesstays constantD.stays constantstays
constant(Total 1 mark)50.Which statement is true about using
sulfuric acid as a catalyst in the following reaction?CH3COCH3(aq)
+ I2(aq) CH3COCH2I(aq) + HI(aq)I.The catalyst increases the rate of
reaction.II.The catalyst lowers the activation energy for the
reaction.III.The catalyst has been consumed at the end of the
chemical reaction.A.I and II onlyB.I and III onlyC.II and III
onlyD.I, II and III(Total 1 mark) 51.Graphing is an important
method in the study of the rates of chemical reaction. Sketch a
graph to show how the reactant concentration changes with time in a
typical chemical reaction taking place in solution. Show how the
rate of the reaction at a particular time can be determined.(Total
4 marks) 52.(a)A solution of hydrogen peroxide, H2O2, is added to a
solution of sodium iodide, NaI, acidified with hydrochloric acid,
HCl. The yellow colour of the iodine, I2, can be used to determine
the rate of reaction.H2O2(aq) + 2NaI(aq) + 2HCl(aq) 2NaCl(aq) +
I2(aq) + 2H2O(l) The experiment is repeated with some changes to
the reaction conditions. For each of the changes that follow,
predict, stating a reason, its effect on the rate of
reaction.(i)The concentration of H2O2 is increased at constant
temperature.(2) (ii)The solution of NaI is prepared from a fine
powder instead of large crystals.(2)(b)Explain why the rate of a
reaction increases when the temperature of the system
increases.(3)(Total 7 marks) 53.Two species, P and Q, react
together according to the following equation.P + Q RThe accepted
mechanism for this reaction isP + P P2fastP2 + Q R + PslowWhat is
the order with respect to P and Q?PQA.11B.12C.21D.22(Total 1 mark)
54.The activation energy of a reaction may be determined by
studying the effect of a particular variable on the reaction rate.
Which variable must be changed?A.pHB.ConcentrationC.Surface
areaD.Temperature(Total 1 mark)55.Consider the following reaction
studied at 263 K.2NO(g) + Cl2(g) 2NOCl(g)It was found that the
forward reaction is first order with respect to Cl2 and second
order with respect to NO. The reverse reaction is second order with
respect to NOCl. (i)State the rate expression for the forward
reaction.(1) (ii)Predict the effect on the rate of the forward
reaction and on the rate constant if the concentration of NO is
halved.(2) (iii)1.0 mol of Cl2 and 1.0 mol of NO are mixed in a
closed container at constant temperature. Sketch a graph to show
how the concentration of NO and NOCl change with time until after
equilibrium has been reached. Identify the point on the graph where
equilibrium is established.(4)(Total 7 marks) 56.Consider the
following reaction.NO2(g) + CO(g) NO(g) + CO2(g)Possible reaction
mechanisms are:Above 775 K:NO2 + CO NO + CO2slowBelow 775 K:2NO2 NO
+ NO3slowNO3 + CO NO2 + CO2fastBased on the mechanisms, deduce the
rate expressions above and below 775 K.(Total 2 marks) 57.State two
situations when the rate of a chemical reaction is equal to the
rate constant.(Total 2 marks) q 58.Consider the following graph of
ln k against for the first order decomposition of N2O4 into NO2.
Determine the activation energy in kJ mol1 for this reaction.(Total
2 marks)59.Excess magnesium, was added to a beaker of aqueous
hydrochloric acid. A graph of the mass of the beaker and contents
was plotted against time (line 1).What change in the experiment
could give line 2?A.The same mass of magnesium in smaller
piecesB.The same volume of a more concentrated solution of
hydrochloric acidC.A lower temperatureD.A more accurate instrument
to measure the time(Total 1 mark) 60.Which quantities in the
enthalpy level diagram are altered by the use of a catalyst?A.I and
II onlyB.I and III onlyC.II and III onlyD.I, II and III(Total 1
mark)61.What is the order of reaction with respect to NO2(g) and
F2(g) given the following rate data at a certain
temperature?[NO2(g)] / mol dm3[F2(g)] / mol dm3Rate / mol dm3
min10.10.20.10.20.20.40.10.40.2Order with respect to NO2(g)Order
with respect to
F2(g)A.firstfirstB.firstsecondC.secondfirstD.secondsecond(Total 1
mark) 62.Nitrogen(II) oxide reacts with hydrogen according to the
following equation:2NO(g) + 2H2(g) N2(g) + 2H2O(g)The table shows
how the rate of reaction varies as the concentrations of the
reactants are changed.ExperimentInitial [NO] /mol dm3Initial [H2]
/mol dm3Initial rate /mol (N2) dm3
s110.1000.1002.5310620.1000.2005.0510630.2000.1001.0110540.3000.1002.28105(a)Determine
the order of reaction with respect to H2 and with respect to NO.H2
................................................................................................................................NO
..............................................................................................................................(2)(b)Write
the rate expression for the
reaction......................................................................................................................................(1)
(c)Calculate the value for the rate constant, and state its units
using the data from
experiment1.....................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................(2)(d)A
suggested mechanism for this reaction is as follows.H2 + NO Xfast
stepX + NO Y + H2Oslow stepY + H2 N2 + H2Ofast stepState and
explain whether this mechanism agrees with the experimental rate
expression in
(b).........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................(4)
(e)Explain why a single step mechanism is unlikely for a reaction
of this
kind.....................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................(2)
(f)Deduce and explain how the initial rate of formation of H2O
compares with that of
N2.....................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................(2)(Total
13 marks)
