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Unit 2: Energetics, Group Chemistry,
Halogenoalkanes and Alcohols
Halogenoalkanes and Alcohols
Topic 9: Introduction to Kinetics and Equilibria
For both AS and A Level students
Q1. Answer the question with a cross in the box you think is correct .
If you change your mind about an answer, put a line through the box and then mark your new answer with a cross .
The rate of a reaction doubles for each 10 K increase in temperature.
If the temperature of this reaction is increased from 298 K to 358 K the rate of the reaction increases by a factor of
A 6
B 12
C 36
D 64
Use this space for any rough working.
Anything you write in this space will gain no credit.
(Total for question = 1 mark)
Q2. Answer the question with a cross in the box you think is correct .
If you change your mind about an answer, put a line through the box and then mark your new answer with a cross .
The graph shows how the concentration of a reactant changes with time.
Which expression gives the best estimate for the value of the rate of this reaction at time b?
A b ÷ c
B d ÷ a
C e ÷ a
D e ÷ b
(Total for question = 1 mark)
Q3. Answer the question with a cross in the box you think is correct .
If you change your mind about an answer, put a line through the box and then mark your new answer with a cross . Hydrogen peroxide decomposes in the presence of a catalyst.
(a) What type of reaction occurs? (1)
A displacement
B disproportionate
C elimination
D hydrolysis
(b) In an experiment, the volume of oxygen produced by the decomposition of hydrogen peroxide was measured at various times as the reaction progressed and a graph was plotted.
The initial gradient of the graph was 0.50 cm3 s −1 .
What is the initial rate of decomposition of hydrogen peroxide in mol s–1?
[Molar volume of a gas at r.t.p. = 24 dm3 mol–1 ] (1)
A 2.1 × 10–2 mol s–1
B 4.2 × 10–5 mol s–1
C 2.1 × 10–5 mol s–1
D 1.0 × 10–5 mol s–1
(Total for question = 2 marks)
Q4. Answer the questions with a cross in the boxes you think are correct .
If you change your mind about an answer, put a line through the box and then mark your new answer with a cross . Hydrogen peroxide decomposes as shown.
2H2O2(aq) → 2H2O(l) + O2(g)
(a) A catalyst increases the rate of decomposition by (1)
A increasing the average kinetic energy of the H2O2 molecules
B decreasing the average kinetic energy of the H2O2 molecules
C increasing the activation energy of the reaction
D decreasing the activation energy of the reaction
(b) A bottle of hydrogen peroxide is labelled as '10 volume'.
This means that 1 cm3 of hydrogen peroxide solution decomposes to produce 10 cm3 oxygen at room temperature and pressure (r.t.p.).
What is the concentration of 10 volume hydrogen peroxide, in mol dm−3?
2H2O2(aq) → 2H2O(l) + O2(g)
[Molar volume of gas at r.t.p. = 24 000 cm3 mol−1 ] (1)
A 0.100
B 0.208
C 0.417
D 0.833
Use this space for any rough working.
Anything you write in this space will gain no credit.
(Total for question = 2 marks)
Q5. Answer the questions with a cross in the boxes you think are correct .
If you change your mind about an answer, put a line through the box and then mark your new answer with a cross .
A solution containing 0.100 mol of hydrochloric acid is added to 8.43 g of magnesium carbonate.
(a) What is the total volume (at r.t.p.) of carbon dioxide formed?
[Mr(MgCO3) = 84.3 Molar volume of a gas at r.t.p. = 24.0 dm3 mol–1 ] (1)
A 2.40 dm3
B 1.20 dm3
C 2400 dm3
D 1200 dm3
(b) Which sketch graph shows the volume of carbon dioxide (y-axis) plotted against time (x-axis) during the reaction? (1)
Q6. Answer the question with a cross in the box you think is correct .
If you change your mind about an answer, put a line through the box and then mark your new answer with a cross .
The energy profile for a reaction is shown.
What is the minimum energy needed for this reaction to occur?
A X
B Y
C X − Y
D X + Y
(Total for question = 1 mark)
Q9. Magnesium metal reacts with hydrochloric acid.
Which change in condition would have no effect on the initial rate of this reaction? (1)
A an increase in the volume of acid solution
B a decrease in the temperature of the acid solution
C an increase in the surface area of the magnesium
D a decrease in the concentration of the acid solution
(Total for question = 1 mark)
Q7. Answer the question with a cross in the box you think is correct .
If you change your mind about an answer, put a line through the box and then mark your new answer with a cross .
The solid line on the graph below shows the Maxwell–Boltzmann distribution for an uncatalysed reaction.
Ea is the activation energy of this reaction.
Q8. The diagram shows the general shape of a Maxwell-Boltzmann distribution curve for the particles present in a reaction mixture.
(b) The activation energy of an uncatalysed reaction is represented by the vertical line, Ea, on the horizontal axis.
The shaded areas A and B are the areas under the curve on either side of the line Ea.
How do the two shaded areas change, if at all, when a catalyst is added? (1)
Q9. This question is about calcium carbonate, CaCO3. Calcium carbonate decomposes on heating.
CaCO3(s) → CaO(s) + CO2(g)
(b) Calcium carbonate reacts with dilute hydrochloric acid.
CaCO3(s) + 2HCl(aq) → CaCl2(aq) + CO2(g) + H2O(l)
A student determines the initial rate of this reaction by collecting the carbon dioxide in a gas syringe and measuring the volume at regular time intervals.
(i) The gas syringe can measure a maximum of 100 cm3 of gas.
Calculate the maximum volume of 0.500 mol dm−3 hydrochloric acid that can be added to excess calcium carbonate at room temperature and pressure (r.t.p.) without exceeding the measurable volume of the gas syringe.
[Molar volume of gas at r.t.p. = 24 000 cm3 mol−1 ] (3)
(iii) The student repeats the experiment but uses hydrochloric acid with a concentration of 0.250 mol dm−3 .
All other variables are kept the same.
State what would happen to the initial rate of reaction and the final volume of carbon dioxide collected. (1)
Initial rate of reaction .............................................................................................................................................
Final volume of carbon dioxide collected .................................................................................................................................
(Total for question = 7 marks)
Q10. This question is about ethanol and bioethanol.
The main fuel used as a petrol substitute is bioethanol.
Bioethanol is ethanol that has been produced by fermentation.
The starting material is usually some form of plant material rich in starch, such as wheat, maize or potatoes.
Enzymes in yeast convert this material to simple carbohydrates such as glucose (C6H12O6) and then to ethanol and carbon dioxide.
C6H12O6 → 2CH3CH2OH + 2CO2
The mixture is left for several days until fermentation is complete.
The percentage of ethanol is never greater than 15 % because higher concentrations of ethanol kill the yeast.
A common blend of fuel is 95 % petrol and 5 % bioethanol.
The engine does not need to be modified for this mixture.
(e) Ethanol can also be produced by the hydration of ethene.
CH2 = CH2(g) + H2O(g) ↔ CH3CH2OH(g) ΔH = − 45 kJ mol−1
(ii) The rate of this reaction is increased by using a catalyst of phosphoric acid.
Label the axes on the Maxwell–Boltzmann distribution curve and use it to explain how a catalyst increases the rate of reaction.
(f) Catalysts such as phosphoric acid are bonded to a support material that contains lots of pores.
(i) Suggest the advantage of using support materials containing lots of pores. (1) ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................
(ii) Under these conditions, only about 5 % of the ethene is converted into ethanol as it passes over the catalyst.
Suggest how the overall yield of this process can be improved to make it economically viable. (2) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................
(Total for question = 7 marks)
Q11. For each question, select one answer from A to D and put a cross in the box .
If you change your mind about an answer, put a line through the box and then mark your new answer with a cross .
Which conditions give the highest yield for the forward reaction?
NH4Cl(s) ↔ NH3(g) + HCl(g)
ΔH = +176 kJ mol−1
A high temperature, high pressure
B high temperature, low pressure
C low temperature, high pressure
D low temperature, low pressure
(Total for question = 1 mark)
Q12. For each question, select one answer from A to D and put a cross in the box .
If you change your mind about an answer, put a line through the box and then mark your new answer with a cross .
Nitrogen dioxide and dinitrogen tetroxide exist in equilibrium.
When an equilibrium is set up in a gas syringe, the mixture is pale brown.
When the mixture is compressed the colour becomes
A darker
B lighter
C darker and then lighter
D lighter and then darker
(Total for question = 1 mark)
Q13. Answer the question with a cross in the box you think is correct .
If you change your mind about an answer, put a line through the box and then mark your new answer with a cross .
A mixture of hydrogen and iodine is left in a sealed container at 300°C until equilibrium is established.
H2(g) + I2(g) ↔ 2HI(g)
The equilibrium mixture is then cooled and the colour of the mixture darkens.
Which is correct?
Q14. The equilibrium reaction shown in the equation was studied by placing the components into a sealed glass container.
At equilibrium, which of the following statements is not true? (1)
A the concentrations of the NO2(g) and N2O4(g) both remain constant
B the total number of molecules is constant
C the forward and reverse reactions have both stopped
D the rate of the forward reaction is equal to the rate of the reverse reaction
(Total for question = 1 mark)
Q15. The equation for a reversible reaction is shown.
What effect will each change have on the rate of reaction and the equilibrium yield of phosphorus(V) chloride?
(a) Increasing the temperature at constant pressure. (1)
Q16. Ethanol can be made in industry by the reaction of ethene with steam, using a phosphoric(V) acid catalyst. CH2=CH2(g) + H2O(g) CH3CH2OH(g)
ΔrH = −45 kJ mol−1 The reaction is carried out at 300°C and 60 atm.
An initial yield of 5 % is achieved when the ethene and steam first pass through the reactor.
*(a) Explain the chemical reasons for the conditions used and why such a low initial yield is acceptable in the industrial process. (6)
............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................
(b) The product of the reaction is a mixture of ethanol and water. Explain why ethanol and water mix together fully.
You may find it helpful to draw a diagram. (3)
............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................
(Total for question = 9 marks)