Syllabus Edition
First teaching 2020
Last exams 2024
Dinitrogen tetraoxide, N2O4, and nitrogen dioxide exist in equilibrium. This is represented by the reaction below:
2NO2 (g) ⇌ N2O4 (g) ∆H = -57 kJ mol-1
Which conditions give the greatest percentage of NO2 at equilibrium?
High pressure and high temperature
Low pressure and high temperature
High pressure and low temperature
Low pressure and low temperature
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Sulphuric acid is manufactured via a series of reactions in the Contact process. The reaction for the main reaction is shown below.
2SO2 (g) + O2 (g) ⇌ 2SO3 (g) ∆H= -197 kJ mol-1
Which statement about the reaction is correct?
Iron is used as a catalyst.
Increased temperature gives a higher yield of SO2.
Increased temperature gives a higher yield of SO3.
Increased pressure gives a higher yield of SO2.
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Which statement below best describes a dynamic equilibrium?
The rate of the forward reaction is equal to the backwards reaction, and the concentrations of reactants and products is constant.
The rate of the forward reaction is equal to the backwards reaction in a closed system, and the concentrations of the reactants and products are equal.
The rate of the forward reaction is equal to the backwards reaction in a closed system, and the concentrations of the reactants and products is constant.
The rate of reaction changes in either direction to counteract a change in conditions.
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An equilibrium is set up in a closed container between equal volumes of gaseous reactants A and B to form a gaseous product C.
The total pressure within the container at 50℃ is 3 atm.
A (g) + B (g) ⇌ 2C (g)
The equilibrium partial pressure of A at 50℃ is 0.5 atm
What is the partial pressure of C at this temperature?
2.5
2.75
1
2
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The Haber process is used to produce ammonia from nitrogen and hydrogen on an industrial scale. The diagram below represents the Haber process.
What is the purpose of the heat exchanger?
To cool the incoming gas mixture to avoid overheating the catalyst.
To cool the reaction products and separate the ammonia from unused nitrogen and hydrogen.
To warm the incoming gas mixture to get more ammonia.
To cool the incoming gas mixture and speed up reaction.
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Ethanol is manufactured by reacting steam with ethene.
C2H4 (g) + H2O (g) ⇌ C2H5OH (g) ∆H = -45 kJ mol-1
What would increase the equilibrium yield of ethanol in this process?
1. Adding a catalyst.
2. Increasing the pressure.
3. Decreasing the temperature.
1 and 2
1 and 3
2 and 3
1, 2 and 3
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Propyl ethanoate is formed in an esterification reaction. How can the value of the equilibrium constant Kc be increased?
Propan-1-ol + ethanoic acid ⇌ propyl ethanoate + water ∆H= -10 kJ mol-1
Increasing the temperature
Adding a catalyst
Increasing the pressure
Lowering the temperature
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In the reaction where gaseous iodine reacts with hydrogen, an equilibrium is established at 450℃. The reaction is exothermic.
H2 (g) + I2 (g) ⇌ 2HI (g)
colourless purple colourless
Which change in conditions will cause the purple colour of the equilibrium mixture to become paler?
Decrease in pressure
Decrease in temperature
Increase in pressure
Increase in temperature
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For the equilibrium 2A (g) + B (g) ⇌ 2C (g) ∆H = +6.5 kJ mol-1, what will change the value of Kp?
Adding a catalyst
Decreasing the pressure
Increasing the pressure
Increasing the temperature
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An equilibrium is established in the reaction.
AB (aq) + CD (aq) ⇌ AC (aq) + BD (aq) ∆H= +180 kJ mol-1
Which factors would affect the value of Kc in this equilibrium?
Change in temperature in the absence of a catalyst
Change in pressure in the presence of a catalyst
Increasing the concentration of AB (aq)
Increasing the concentration of AC (aq)
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Use of the periodic table is relevant to this question.
A sample of potassium oxide, K2O, is dissolved in 500 cm3 of distilled water. 25.0 cm3 of this solution is titrated against sulfuric acid of concentration 1.5 mol dm–3. 20.0 cm3 of this sulfuric acid is needed for complete neutralisation.
What is the mass of potassium oxide was originally dissolved in 500 cm3 of distilled water?
2.83 g
28.3 g
47.1 g
56.6 g
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A dynamic equilibrium was set up between carbon monoxide hydrogen and methanol in a 2 dm3 sealed vessel at a constant temperature.
CO (g) + 2H2 (g) ⇌ CH3OH (g)
The number of moles of each gas at equilibrium was, carbon monoxide 6.20 x 10-3, hydrogen 4.80 x 10-3, methanol 5.20 x 10-5.
Where has the equilibrium shifted, and what is the value for Kc at this temperature?
To the right, Kc = 364
To the left, Kc = 364
To the left, Kc = 1456.1
To the right, Kc = 1456.1
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Gaseous reactants A and B react to form a gaseous product C in a 1: 3: 2 ratio in a 5 dm3 container. In an experiment, 1.0 mol of A and 1.0 mol of B are used, and the reaction is heated until equilibrium is reached. At equilibrium, only 10% of A had reacted.
What is the equilibrium concentration of product C at this temperature?
0.18 mol dm-3
0.02 mol dm-3
0.04 mol dm-3
0.2 mol dm-3
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Four molecules of oxygen can bind to one molecule of haemoglobin, Hb, according to the following equation.
Hb (aq) + 4O2 (aq) ⇌ Hb (O2)4 (aq)
At equilibrium, the concentration of oxygen is 6.7 x 10-6 mol dm-3 and the equilibrium concentrations of Hb and Hb(O2)4 are the same.
What is the value of Kc for this equilibrium?
5 x 1020 mol-4 dm12
1.3 x 105 mol-4 dm12
7.6 x 10-6 mol-4 dm12
3.3 x 10-21 mol-4 dm12
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An aqueous solution was prepared containing 1.0 mol of silver nitrate and 1.0 mol of iron sulphate (II) in a 2.00 dm3 container. When equilibrium was established, there was a 0.44 mol of silver ions in the mixture.
Ag+ (aq) + Fe 2+ ⇌ Ag (s) + Fe3+ (aq)
What is the numerical value of Kc?
5.79
5.79 mol-1 dm3
1.27 mol-1 dm3
1.27
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560 kg of nitrogen and 120 kg of hydrogen are pressurized, heated and passed over an iron catalyst. When the mixture of gases reaches equilibrium, it contains 96 kg of hydrogen.
What mass of ammonia will it contain?
1.36 x 102
2.04 x 105
1.36 x 105
2.72 x 105
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The percentage yield of ammonia produced if the equilibrium was established during the Haber process is plotted against the operating pressure for two temperatures, 400˚C and 500˚C.
Which diagram correctly represents the two graphs?
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Equimolar quantities of strontium carbonate and magnesium carbonate are heated separately, resulting in complete thermal decomposition. The minimum temperature for the reaction to occur is called Td.
The cold residues are separately added to equal volumes of water, and the change in pH is measured. The change in pH is called ∆pH.
Which metal has the highest value of Td, and the greater value of ∆pH?
|
Td |
∆pH |
|
|
A B C D |
Sr Sr Mg Mg |
Mg Sr Mg Sr |
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Shown below are two equilibria.
The numerical value for Kc in reaction I is 2.
Reaction I 2A2 (g) + B2 (g) ⇌ 2A2B (g)
Reaction II A2B (g) ⇌ A2 + 
B2 (g)
Under the same conditions, what is the numerical value of Kc for reaction II?
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1
4
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The following equilibrium is set up in a mixture of sulfuric acid and concentrated nitric acid.
H2SO4 + HNO3 ⇌ HSO4- + H2NO3+
Which row correctly describes the behaviour of each molecule within the equilibrium?
|
H2SO4 |
HNO3 |
HSO4– |
H2NO3+ |
|
|
A B C D |
Acid Base Acid Acid |
Acid Acid Base Base |
Base Acid Base Acid |
Base Base Acid Base |
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At 450℃ the value for Kc for the below reaction is 60.
H2 (g) + I2 (g) ⇌ 2HI (g)
The equilibrium moles of H2 and I2 are 2 mol and 0.3 mol, respectively.
How many moles of HI (g) is present at equilibrium?
6
0.001
36
0.1
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Ethyne and hydrogen are formed from methane, and a dynamic equilibrium is established.
2CH4 (g) ⇌ 3H2 + C2H2 (g)
What are the units for Kc?
mol dm-3
mol2 dm-6
mol3 dm-9
mol4 dm-12
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Upon heating, dinitrogen tetroxide will dissociate into nitrogen dioxide.
N2O4 (g) ⇌ 2NO2 (g)
At a particular temperature, the equilibrium partial pressure of nitrogen dioxide was 0.67 atm and dinitrogen tetroxide 0.33 atm.
What is the numerical value of Kp at this temperature?
1.36
0.49
0.65
2.03
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Nitrogen monoxide and oxygen can be formed from the thermal decomposition of nitrogen dioxide.
2NO2 (g) ⇌ 2NO (g) + O2 ( g)
In an experiment 4 mol of nitrogen dioxide were put into a 1 dm3 container and heated to a constant temperature. The equilibrium mixture contains 0.8 mol of oxygen.
What is the value of the equilibrium constant, Kc, at the temperature of the experiment?
0.82 x 0.8 / 42
1.6 x 0.8 / 2.42
1.62 x 0.8 / 2.4
1.62 x 0.8 / 2.42
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The Contact process is used for the industrial production of sulfuric acid. The three main chemical reactions involved in the contact process are listed below.
S (s) + O2 (g) → SO2 (g)
SO2 (g) + O2 (g) → SO3 (g)
SO3 (g) + H2O (l) → H2SO4 (l)
Which statement about this process is correct?
In the first stage, a large excess of air under high pressure is used to improve the yield.
Two of the three stages are equilibria.
All three stages are exothermic.
In the final stage, SO3 is absorbed by water droplets.
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The dissociation of gas X2Y4 into XY2 is represented in the equation below.
X2Y4 (g) ⇌ 2XY2 (g) ΔHθ = + 60 kJ mol-1
At constant pressure, if the temperature of the equilibrium mixture of the gases is increased, will the volume of the mixture increase or decrease and why?
The volume will increase, but only because of a shift of equilibrium towards the right.
The volume will increase, both because of a shift of equilibrium towards the right and also because of thermal expansion.
The volume will stay the same because any thermal expansion could be exactly counteracted by a shift of equilibrium towards the left.
The volume will decrease because a shift of equilibrium towards the left would more than counteract any thermal expansion.
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The table gives the concentrations and pH values of the aqueous solutions of two compounds, P and Q. Either compound could be an acid or a base.
|
P |
Q |
|
|
Concentration pH |
2 mol dm–3 9 |
2 mol dm–3 6 |
Student X concluded that Q is a strong acid.
Student Y concluded that the extent of dissociation is lower in Q (aq) than in P (aq).
Which of the students are correct?
X only
Y only
Both X and Y
Neither X nor Y
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A compound, WX, will dissociate into an X- ion and a W+ ion in solution. This is represented by the equation below.
WX (aq) ⇌ X- (aq) + W+ (aq)
2 dm3 of a 0.4 mol solution of WX was heated to a constant temperature until equilibrium was established. The equilibrium mixture is found to contain 0.1 mol of the W+ ion.
What is the correct expression for the equilibrium constant Kc.
0.12 / 0.3
0.15 / 0.052
0.052 / 0.15
0.05 / 0.15
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Ammonia is produced from hydrogen and nitrogen in the Haber process.
N2 (g) + 3H2 (g) ⇌ 2NH3 (g)
A mixture of 2.00 mol of nitrogen, 3.00 mol of hydrogen and 1.98 mol of ammonia is allowed to reach equilibrium in a sealed container with a volume of 1 dm3 under certain conditions. It was found that 1.64 mol of ammonia were present in the equilibrium mixture.
What is the value of Kc under these conditions?
0.10
0.03
0.22
2.17
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When 5.00 mol of A reacts with 5.00 moles of B in a sealed vessel of volume 1 dm3 and total pressure of 1.5 atm an equilibrium is established which contains 3.00 moles of C.
A + B ⇌ 2C
What is the equilibrium partial pressure of A?
2.00 atm
0.525 atm
0.350 atm
0.450 atm
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