Download Multiple-choice questions : 1. The following graph shows the volume

Multiple-choice questions :
The following graph shows the volume of hydrogen gas produced against time.
Volume of hydrogen gas (cm3)
1.
Time of reaction (min)
Which of the following statements about the above graph is INCORRECT?
A.
B.
C.
D.
2.
The average rate of the reaction is about 7.25 cm3 min1.
The average rate between t = 1 min and t = 3 min is about 13.5 cm3 min1.
The instantaneous rate at t = 1 min is about 23.0 cm3 min1.
The instantaneous rate at t = 2 min is about 21.0 cm3 min1.
□
Which of the following statements concerning a rate curve is/are true?
(1) The initial rate must be the fastest.
(2) If the slope of the tangent equals zero, then the reaction stops.
(3) The slope of the tangent must decrease from the largest value to zero.
A. (1) only
B.
C.
D.
(2) only
(1) and (3) only
(2) and (3) only
□
1
3.
The rate curve of the amount of carbon dioxide produced when an acid reacts
with a carbonate is plotted. When is the rate of the reaction the fastest?
A. The graph is the steepest.
B.
C.
D.
The graph is at 45 to the horizontal.
The graph is half finished.
The graph is horizontal.
□
4.
Which of the following methods are possible to quench a reaction?
(1) Cooling the reaction mixture with an ice bath
(2) Removing one or more of the reactant(s)
(3) Diluting the reaction mixture
(4) Adding a catalyst
A. (1), (2) and (3)
B.
C.
D.
(1), (2) and (4)
(1), (3) and (4)
(2), (3) and (4)
□
5.
The rate of formation of O3(g) is 2.0 × 107 mol dm3 s1 for the reaction:
3O2(g)  2O3(g)
What is the rate of disappearance of O2(g) in mol dm3 s1?
A. 1.3 × 107
B. 2.0 × 107
C. 3.0 × 107
D. 4.5 × 107
□
6.
Which of the following statements is correct for the reaction below?
A.
B.
4P + Q  2R + 2S
The rate of formation of R is one half the rate of disappearance of Q.
The rate of decrease of Q is one quarter of the rate of disappearance of P.
C.
D.
The rates of formation of R and S are not equal.
The rate of formation of S is double the rate of disappearance of P.
□
2
What is the initial rate of the reaction (in mol dm3 s1) represented by this
graph?
Concentration (M)
7.
Time
(s)
A.
0.08
B.
C.
0.08
0.02
D.
0.02
□
8.
Which of the following diagrams shows a correct rate curve for a chemical
reaction?
A.
B.
Amount of product
in the reaction
Amount of product
in the reaction
Time
Time
C.
D.
Amount of product
in the reaction
Amount of product
in the reaction
Time
Time
3
□
9.
2MnO4
+ 5H2O2(aq) + 6H (aq)  2Mn (aq) + 8H2O(l) + 5O2(g)
Which of the following methods is/are possible for monitoring the progress of
the above reaction?
(1) Titrimetric analysis
(2) Measuring the change in colour intensity by colorimetry
(3) Measuring the change in volume of gas
A. (1) and (2) only
B. (1) and (3) only
C. (2) and (3) only
D. (1), (2) and (3)
(aq)
+
2+
□
10. Which of the following methods can be used to determine the reaction rate of the
following reaction?
Cr2O72(aq) + 14H+(aq) + 3C2O42(aq)  6CO2(g) + 7H2O(l) + 2Cr3+(aq)
(1) Measuring volume of CO2 formed
(2) Measuring time for pH change
(3) Measuring time for the colour of the solution to change from orange to
green
A. (1) and (2) only
B. (1) and (3) only
C.
D.
(2) and (3) only
(1), (2) and (3)
□
11. Which of the following statements concerning the collision theory are correct?
(1) Reactant particles must collide to trigger a reaction.
(2) Products can only be formed if the collision is in the right orientation,
regardless of the speed of the reactant particles.
(3) Only a small fraction of collisions is classified as effective collisions.
A. (1) and (2) only
B.
C.
D.
(1) and (3) only
(2) and (3) only
(1), (2) and (3)
□
4
12. In the graphs below, curve (i) was obtained when 3 g of zinc granules was reacted
with excess 2.0 M hydrochloric acid. Curves (ii) and (iii) were obtained after making
changes to the acid.
Curve (ii): Excess 1.0 M nitric acid
Curve (iii): Excess 1.5 M sulphuric acid
Which of the following graphs matches the rate curves (i), (ii) and (iii) correctly?
A.
Volume
of H2(g)
ii
i
iii
Time
B.
Volume
of H2(g)
ii
i
iii
Time
C.
Volume
iii
of H2(g)
i
ii
Time
D.
Volume
of H2(g)
iii
i
ii
Time
5
□
13. Zinc metal reacts with excess 1.0 M HCl according to the following equation:
Zn(s) + 2H+(aq)  Zn2+(aq) + H2(g)
Which of the following changes will increase the rate of evolution of H2(g)?
(1) Using zinc dust instead of chunks.
(2) Using 200 cm3 of 1.0 M HCl in place of 100 cm3.
(3) Using 2.0 M HCl instead of 1.0 M HCl.
A. (1) only
B. (2) only
C. (1) and (3) only
D. (2) and (3) only
□
14. Consider the reaction of excess dilute hydrochloric acid and magnesium ribbon,
which of the following parameters is/are NOT changed upon changes in the
concentration of the hydrochloric acid, given other factors are kept constant?
(1) The total heat energy released from the reaction mixture
(2) The time taken for the reaction to complete
(3) The total volume of gas collected
A. (1) only
B. (2) only
C. (1) and (3) only
D.
(2) and (3) only
□
15. Consider the following reaction:
S2O32(aq) + 2H+(aq)  SO2(g) + H2O(l) + S(s)
A white tile with a black cross marked on it was placed under a beaker. 50.0 cm3
of 0.10 M sodium thiosulphate solution and 10.0 cm3 of 1.0 M hydrochloric acid
were mixed in the beaker. Sulphur was produced and the cross was blocked.
Which of the following changes can make the cross disappear in a shorter time?
(1) Warm the reagents before the reaction.
(2)
(3)
A.
B.
C.
D.
Use 100 cm3 of 0.10 M sodium thiosulphate solution instead.
Use 20.0 cm3 of 2.0 M hydrochloric acid instead.
(1) only
(2) only
(1) and (3) only
(2) and (3) only
□
6
16. When temperature is increased, which of the following concerning collisions of
reactant particles will occur?
(1) There will be a larger number of effective collisions.
(2) There will be a larger number of ineffective collisions.
(3) Reactant particles will have a higher average kinetic energy.
A. (1) and (2) only
B. (1) and (3) only
C. (2) and (3) only
D. (1), (2) and (3)
□
17. When the surface area of a solid reactant is increased, which of the following
concerning the reactant particles will NOT occur?
(1) There will be a larger number of collisions.
(2)
(3)
A.
B.
C.
D.
Reactant particles will have a greater amount of average kinetic energy.
There will be a larger fraction of effective collisions.
(1) and (2) only
(1) and (3) only
(2) and (3) only
(1), (2) and (3)
□
18. Which of the following factors determine(s) the rate of a chemical reaction?
(1) Molar mass of reactants added
(2) Average kinetic energy of reactant particles
(3) Surface area of solid reactants
A. (1) only
B. (2) only
C. (1) and (3) only
D. (2) and (3) only
□
7
Mass
19. Excess magnesium was added to a beaker of aqueous hydrochloric acid on a
balance. A graph of the mass of the beaker and contents was plotted against time
(curve 1).
1
2
Time
Which of the following changes in the experiment could give curve 2?
(1) The same mass of magnesium but in smaller pieces
(2)
(3)
A.
B.
C.
D.
The same volume of a more concentrated solution of hydrochloric acid
A lower temperature
(1) only
(2) only
(1) and (3) only
(2) and (3) only
□
20. Catalyst is an important chemical that can increase the reaction rate greatly.
Which of the following reactions and catalysts are correctly matched?
Reaction
(1) 2SO2(g) + O2(g)
(2) N2(g) + 3H2(g)
Catalyst
2SO3(g)
Pt
2NH3(g)
Fe
(3) 2H2O2(aq)  2H2O(l) + O2(g)
A.
B.
C.
(1) and (2) only
(1) and (3) only
(2) and (3) only
D.
(1), (2) and (3)
MnO2
□
8
21. The following set-up is used to investigate the decomposition of hydrogen
peroxide.
2H2O2(aq)  2H2O(l) + O2(g)
stopwatch
cotton wool
a small amount of
solid MnO2
measured volume of standard
H2O2(aq)
electronic balance
A graph of the mass of the reaction mixture against time was plotted. Which of
the following curves would be obtained?
Mass of
reaction
A
B
C
mixture
D
Time
□
22. Consider the following chemical reaction:
2NaN3(s)  2Na(s) + 3N2(g)
It was found that 0.524 g of NaN3 decomposes to form 0.290 dm3 of nitrogen gas
at a certain temperature and pressure. What is the molar volume of N2 at that
temperature and pressure?
A.
B.
C.
D.
22.8 dm3 mol1
23.5 dm3 mol1
24.0 dm3 mol1
25.3 dm3 mol1
□
9
23. 4NH3(g) + 5O2(g)  4NO(g) + 6H2O(g)
At constant temperature and pressure, what is the maximum volume of NO that
can be produced from 14.0 dm3 of NH3 and 16.0 dm3 of O2?
A. 12.8 dm3
B. 14.0 dm3
C. 17.5 dm3
D. 20.0 dm3
□
24. At a certain temperature and pressure, 3.0 dm3 of sulphur dioxide is reacted with
2.0 dm3 of oxygen according to the equation below.
2SO2(g) + O2(g)  2SO3(g)
What volume of sulphur trioxide (in dm3) was formed at the same temperature
and pressure?
A.
B.
C.
D.
5.0
4.0
3.0
2.0
□
25. Which of the following pairs of gases have the same number of atoms at the
same temperature and pressure?
A.
200 cm3 of steam
200 cm3 of ammonia
B.
1 dm3 of carbon dioxide
1 dm3 of sulphur trioxide
C.
100 cm3 of methane
500 cm3 of neon
D.
50 cm3 of hydrogen chloride
50 cm3 of hydrogen sulphide
□
3
3
26. 30 cm of chlorine is mixed with 70 cm of hydrogen in a test tube with a stopper.
Then the test tube is allowed to expose to sunlight for half an hour. In the
presence of sunlight, chlorine reacts with hydrogen to give hydrogen chloride.
What is the volume of hydrogen chloride produced?
(Assume that all the volumes are measured at r.t.p.)
A. 30 cm3
B. 40 cm3
C. 60 cm3
D. 140 cm3
□
10
27. What is the volume of oxygen required for the complete combustion of 50 cm3 of
methane, CH4 at r.t.p.?
A. 100 cm3
B. 50 cm3
C. 25 cm3
D. 10 cm3
□
28. Which of the following gases has the greatest number of atoms under r.t.p.?
A. 18 dm3 of ammonia
B. 32 dm3 of helium
C.
D.
6.0 dm3 of methane
8.0 dm3 of sulphur trioxide
□
29. What is the number of molecules in 305 cm3 of O2(g) at r.t.p.?
A. 3.83 × 1021
B. 7.64 × 1022
C. 1.53 × 1022
D 7.65 × 1021
□
30. 0.22 g of carbon dioxide occupies a volume of 120 cm3 at r.t.p. What is the
molar mass of carbon dioxide?
A.
B.
C.
D.
43.4 g mol1
43.6 g mol1
43.8 g mol1
44.0 g mol1
□
31. What volume of 0.5 M hydrochloric acid is required to neutralize excess
anhydrous sodium carbonate, with 1200 cm3 of carbon dioxide produced at
r.t.p.?
A.
B.
C.
D.
100 cm3
200 cm3
250 cm3
300 cm3
□
11
32. What is the number of atoms in 2.80 g of carbon monoxide at room temperature
and pressure?
A. 1.20 × 1023
B. 2.01 × 1023
C. 6.02 × 1022
D. 6.02 × 1023
□
33. A student uses hydrochloric acid to react with sodium carbonate at r.t.p. If
hydrochloric acid is the limiting reagent, what volume of carbon dioxide can be
produced from 50 cm3 of 1.0 M hydrochloric acid?
A.
B.
C.
0.60 dm3
1.2 dm3
1.8 dm3
D.
2.4 dm3
□
34. C3H8(g) + 5O2(g)  3CO2(g) + 4H2O(l)
2.0 g of C3H8(g) undergoes complete combustion to give CO2(g) and H2O(l) at
r.t.p.
Calculate the volume of O2 required in this combustion.
A. 24.0 dm3
B.
C.
D.
5.47 dm3
12.0 dm3
3.27 dm3
□
Each question below consists of two separate statements. Decide whether each of
the two statements is true or false; if both are true, then decide whether or not
the second statement is a correct explanation of the first statement. Then select
one option from A to D according to the following table:
A. Both statements are true and the 2nd statement is a correct explanation
of the 1st statement.
B. Both statements are true and the 2nd statement is NOT a correct
explanation of the 1st statement.
C. The 1st statement is false but the 2nd statement is true.
D. Both statements are false.
12
35.
The instantaneous rate of a reaction is
calculated from the slope of the tangent
to the rate curve at t = 0.
The rate curve of most reactions is the
steepest at first and becomes less steep
with time.
□
36.
Sodium carbonate can be used to
quench the reaction between
propanone and iodine.
An acid is used as the catalyst in the
reaction between propanone and iodine.
□
37.
Catalysts can increase the rate of a
chemical reaction.
A catalyst is chemically unchanged at
the end of a reaction.
□
38.
Reaction rate depends on the
concentration of reactants for most
reactions.
Increasing the concentration of the
excess reactant will increase the
reaction rate for most reactions.
□
39.
100 cm3 of oxygen reacts with excess
carbon to give 100 cm3 of carbon
dioxide at r.t.p.
1 mole of oxygen reacts with excess
carbon to give 1 mole of carbon
dioxide at r.t.p..
□
40.
1 dm3 of H2 and 1 dm3 of O2 DO NOT
contain the same number of molecules
According to the Avogadro’s Law, equal
volumes of all gases contain the same
number of molecules only at room
temperature and pressure.
□
at 100C and 2 atm.
13
Conventional questions :
1.
Consider the following reaction:
2NaHCO3(s) + H2SO4(aq)  Na2SO4(aq) + 2H2O(l) + 2CO2(g)
When 3.5 g of sodium hydrogencarbonate was added to 25.0 cm3 of 3.0 M
sulphuric acid, the sodium hydrogencarbonate reacted and disappeared in 180
seconds.
(a) Which of the two reagents is in excess?
(b) Calculate the average rate of decrease of sodium hydrogencarbonate in
g s 1 .
(c) Calculate the average rate of decrease of sulphuric acid in M s1.
(d) Calculate the average rate of production of carbon dioxide in g s1.
[7M]
14
2.
In an experiment of a chemical reaction A + B  C, the amounts of reactant A
recorded at one-minute intervals are shown below.
Time (t)/min
Amount of A/mol
0
1
2
3
4
5
6
0.8
0.4
0.2
0.1
0.05
0.025
0.0125
(a) Calculate the average rate of change in the amount of A in the mixture in
mol min1 throughout the reaction.
(b) Plot a graph of ‘Amount of A’ against ‘Time’.
(c) Calculate, from your graph, the initial rate of reaction.
(d) Calculate, from your graph, the instantaneous rate at the third minute.
[8M]
15
3.
Hydrogen peroxide decomposes according to the following equation:
2H2O2(aq)  2H2O(l) + O2(g)
(a) Suggest ONE method to determine the reaction rate of the above reaction.
(b) Name the catalyst that can speed up this reaction.
(c) If a catalyst is used in the reaction, outline the procedure of a titrimetric
analysis used to follow the progress of the reaction.
(d) Balance the following ionic equation for the titration reaction.
H2O2(aq) + MnO4(aq) + H+(aq)  Mn2+(aq) + H2O(l) + O2(g)
[7M]
16
The graph below shows the volume of carbon dioxide gas produced against time
when excess calcium carbonate is added to x cm3 of 2.0 M hydrochloric acid.
Volume of CO2
4.
Time
(a) Write an ionic equation for the reaction.
(b) State and explain the change in the rate of reaction with time. Give a
method to determine the rate of the reaction at a particular time from the
curve.
(c) Sketch, on the same graph, the curves would be obtained if:
(i) the same volume of 1.0 M HCl is used.
(ii) the volume of 1.0 M HCl used is doubled.
Label the curves and explain your answer in each case.
17
[10M]
5.
A student found that colourless gas bubbles were evolved when a raw egg (with
eggshell) was immersed in vinegar.
(a) Write an equation to show the chemical reaction involved.
(b) The student did the following experiments to investigate the rate of reaction
between eggshell and vinegar. Each experiment was done by adding
eggshell to vinegar in a conical flask and measuring the decrease in mass of
the reaction mixture with time.
Experiment
Reaction conditions
1
3 g of eggshell fragments + 50 cm3 of 2.0 M vinegar
25C
2
3 g of eggshell powder + 50 cm3 of 2.0 M vinegar
25C
3
3
3 g of eggshell powder + 50 cm of 2.0 M vinegar
50C
Sketch, on the same graph, the three curves obtained from the experiments.
(c) Explain the differences in the initial rates between
(i) Experiments 1 and 2.
(ii) Experiments 2 and 3.
18
[11M]
6.
A student carried out five experiments to investigate the factors affecting
reaction rate of the reaction between magnesium and dilute hydrochloric acid.
Five rate curves were obtained from these experiments. Magnesium metal is in
excess in the five experiments. The table below shows the experimental
conditions in each experiment.
Experiment
1
2
3
4
5
Volume of HCl (cm3)
20
75
70
70
50
Concentration of HCl (M)
2.0
2.0
3.0
3.0
3.0
Temperature of HCl (C)
20
35
50
35
35
Size of Mg
ribbons
granules
powder
granules
powder
(a) Explain why sodium is not used to carry out the experiment.
Volume of H2(g)
(b) Assign the following rate curves to their corresponding experiments.
Time
(c) Explain the following phenomena briefly.
(i)
Slaked lime that used to neutralize acid soils is usually in powdered
form.
(ii) Ingredients of soup are usually cut into small pieces.
(iii) Food can be kept longer in a refrigerator.
19
[13M]
7.
The uncatalyzed decomposition of X to Y is represented as X  2Y. The amount
of X decreased as the reaction proceeded was recorded in the following table.
Time (min)
Amount of X (mol)
0
0.010
1
0.0066
2
0.0046
3
0.0030
4
0.0024
5
0.0020
6
0.0020
(a) Plot a graph to determine the initial rate of the reaction (in mol s1).
(b) Sketch, on the same graph, the rate curve that would be obtained if a
catalyst was used in the reaction. Label the new curve as ‘b’ and explain any
difference between the two curves.
(c) The catalyst used in (b) is in the form of granules. Suggest and explain a
method to increase the reaction rate.
20
[8M]
8.
Consider the following reaction:
2H2O2(aq)  2H2O(l) + O2(g)
(a) Oxygen can be prepared by the catalytic decomposition of hydrogen
peroxide. This reaction is catalysed by manganese(IV) oxide.
(i) Explain the term ‘decomposition’.
(ii)
Given that manganese(IV) oxide increases the rate of reaction, state
the criteria to be fulfilled to show that it is a catalyst for this
reaction.
(iii)
Draw the set-up that could be used to prepare and collect oxygen
produced by the decomposition of hydrogen peroxide.
(b) At room temperature and pressure, 100 cm3 of 2.0 M hydrogen peroxide
decomposed in the presence of a catalyst.
(i)
Calculate the number of moles of hydrogen peroxide in 100 cm3 of
2.0 M hydrogen peroxide.
(ii) Calculate the number of moles of oxygen (O2) formed.
(iii) Calculate the volume of oxygen produced.
[8M]
21
9.
Suppose an airship was filled with 4.80 × 103 dm3 of hydrogen gas initially at
r.t.p. In an accident, the hydrogen gas inside the airship was ignited and all of the
hydrogen gas reacted with oxygen in air to form water. (Density of water is 1.0 g
cm3.)
(a) Calculate the number of moles of hydrogen gas present in the airship.
(b) Write a balanced equation for the above reaction.
(c) Calculate the volume of oxygen consumed and water formed at r.t.p.
(d) Suppose air contains 21% by volume of oxygen, calculate the volume of air
required to complete the reaction.
[6M]
22
10. Hydrocarbons undergo complete combustion to give carbon dioxide under
sufficient oxygen supply. Toxic carbon monoxide is produced if the oxygen
supply is insufficient. Catalytic converters are usually installed in vehicles to
minimize the emission of carbon monoxide in exhaust gas.
(a) (i) Balance the following equation:
CH3CH2CH3(g) + O2(g)  CO2(g) + CO(g) + H2O(l)
(ii) Suppose 4.95 g of propane (CH3CH2CH3) gas is introduced. What is
the volume of carbon monoxide produced at r.t.p. from the above
incomplete combustion?
(b) Inside the converter, carbon monoxide is converted to carbon dioxide in the
presence of oxygen. Write a chemical equation for the reaction involved.
(c) (i)
What is the volume of oxygen required at r.t.p. to remove the amount
of carbon monoxide calculated in part (a)(ii)?
(ii) Express the amount of oxygen required in g.
[8M]
23
11. Consider the following reaction:
Mg3N2(s) + 6H2O(l)  3Mg(OH)2(s) + 2NH3(g)
(a) What is the mass of magnesium nitride needed to produce 116.6 g of
magnesium hydroxide?
(b) What volume of ammonia is formed at r.t.p. using the amount of
magnesium nitride specified in part (a)?
(c) What volume of 2.0 M hydrochloric acid is needed to neutralize all the
ammonia gas formed in part (b)?
[8M]
24
Answers :
Multiple-choice questions :
1
2
3
4
5
6
7
8
9
10
D
B
A
A
C
B
B
C
D
D
11
12
13
14
15
16
17
18
19
20
B
C
C
C
C
D
C
D
B
D
21
22
23
24
25
26
27
28
29
30
D
B
A
C
C
C
A
A
D
D
31
32
33
34
35
36
37
38
39
40
B
A
A
B
C
A
B
B
B
D
Conventional questions :
1.
(a) Number of moles of NaHCO3 =
3.5
mol = 0.0417 mol
23.0  1.0  12.0  16.0  3
Number of moles of H2SO4 = 3.0 ×
25.0
mol = 0.0750 mol [1]
1000
From the equation, the mole ratio of NaHCO3 to H2SO4 is 2 : 1.
0.0750 mol of H2SO4 needs 0.150 mol of NaHCO3 to react completely.
∴ H2SO4 is in excess. [1]
(b) The average rate of decrease of sodium hydrogencarbonate =
3. 5
g s1 =
180
0.0194 g s1 [1]
(c) From the equation, the mole ratio of sodium hydrogencarbonate to sulphuric acid
is 2 : 1.
Number of moles of H2SO4 reacted =
Change in concentration of H2SO4 =
0.0417
mol = 0.0209 mol
2
0.0209
M = 0.836 M [1]
25.0
1000
25
Average rate of decrease of H2SO4 =
0.836
M s1 = 4.64 × 103 M s1 [1]
180
(d) From the equation, the mole ratio of sodium hydrogencarbonate to carbon
dioxide is 1 : 1.
Number of moles of CO2 produced = Number of moles of NaHCO3 reacted =
0.0417 mol [1]
Change in mass of CO2 = 0.0417 × (12.0 + 16.0 × 2) g = 1.83 g
Average rate of production of CO2 =
1.83
g s1 = 0.0102 g s1 [1]
180
2.
(a) Average rate of change in the amount of A =
(0.0125  0.8)mol
[1]
(6  0)min
= 0.13 mol min1 [1]
Amount of A (mol)
(b)
Time (min)
For correct labelling of axes [1]
For correct plot of graph [1]
26
Amount of A (mol)
(c)
Time (min)
Initial rate of reaction =
(0.38  0.8)mol
[1] = 0.42 mol min1 [1]
(1  0)min
Amount of A (mol)
(d)
Time (min)
Instantaneous rate of reaction at the third minute =
(0.04  0.17)mol
[1]
(4  2)min
= 0.065 mol min1 [1]
27
3.
(a) Collect the oxygen formed by gas syringe, [1] and record the volume collected at
regular time intervals. [1]
(b) Manganese(IV) oxide [1]
(c) At regular time intervals, [1] withdraw a small portion of the reaction mixture
and filter out the catalyst. [1] Then titrate the small portion of the reaction
mixture against standard acidified potassium permanganate solution. [1]
(d) 5H2O2(aq) + 2MnO4(aq) + 6H+(aq)  2Mn2+(aq) + 8H2O(l) + 5O2(g) [1]
4.
Volume of CO2
(a) CaCO3(s) + 2H+(aq)  Ca2+(aq) + H2O(l) + CO2(g) [1]
(b) The rate decreases with time. [1]
The concentration of the reactants decreases with time so the number of effective
collisions decreases. [1]
Draw a tangent to the curve at time t.
Rate of reaction at time t = slope of the tangent [1]
(c)
original
(ii)
(i)
Time
Correct sketching of curve (i) [1]
Correct sketching of curve (ii) [1]
(i) Volume of CO2 produced is smaller as the amount of HCl is halved. [1]
The curve is less steep since the concentration of HCl is lower. [1]
(ii) Equal volume of CO2 is produced since amount of HCl is unchanged. [1]
The curve is less steep since the concentration of HCl is lower. [1]
28
5.
Decrease in mass
(a) CaCO3(s) + 2CH3COOH(aq)  (CH3COO)2Ca(aq) + CO2(g) + H2O(l) [1]
(b)
3
2
1
Time
Correct curves [3]
(c) (i) Experiment 2 gives a higher initial rate than experiment 1. [1] The powder
provides a larger surface area than the fragments. [1] The higher chance of
collision increases the number of effective collisions and hence the reaction
rate. [1]
(ii) Experiment 3 gives a higher initial rate than experiment 2. [1] The increase
in temperature raises the average kinetic energy of the reactant particles. [1]
They have more energy and move faster. [1] The higher chance of collision
increases the number of effective collisions and hence the reaction rate. [1]
29
Volume of H2(g)
6.
(a) Sodium reacts with hydrochloric acid explosively [1] so the experiment is very
difficult to control. [1]
(b)
3
4
5
2
1
Time
Correct assignment of five curves [5]
(c) (i) Powdered slaked lime has a much larger surface area, [1] so it can
neutralize acid soils much faster. [1]
(ii) The surface area of the ingredients increases, [1] so the cooking process can
be faster. [1]
(iii) The temperature inside the refrigerator is low, [1] so the reactions that lead
to deterioration of food proceed slower. [1]
Amount of X (mol)
7.
(a)
Time (min)
Correct labelling of axes [1]
30
Correct curve [1]
0  0.010
Initial rate =
mol s1 = 6.94 × 105 mol s1 (The negative sign
(2.4  0)  60
means a decrease in the amount of X) [1]
Amount of X (mol)
(b)
‘b’
Time (min)
Correct sketching [1]
The reaction rate is higher when a catalyst is used, so the new curve is steeper
initially and becomes horizontal earlier. [1] The amount of X remained is
unchanged since a catalyst has no effect on the yield of the product. [1]
(c) Use powdered catalyst [1] to increase the surface area of the catalyst [1] and
hence the reaction rate.
31
8.
(a) (i)
Decomposition is a process in which a compound breaks down into two or
more substances, usually as a result of heating. [1]
(ii) It should be regenerated at the end of the reaction [1] and it is used in only
trace amount. [1]
(iii)
gas syringe
oxygen gas
H2O2(aq)
manganese(IV)
oxide
Correct diagram [1]
Correct labelling [1]
(b) (i)
Number of moles of hydrogen peroxide =
100
× 2.0 mol = 0.200 mol [1]
1000
(ii) Mole ratio of H2O2 : O2 = 2 : 1
Number of moles of oxygen (O2) formed =
0.200
mol = 0.100 mol [1]
2
(iii) Volume of oxygen produced = 0.100 × 24.0 dm3 = 2.40 dm3 [1]
9.
4.80  103
(a) Number of moles of H2 present =
mol = 200 mol [1]
24.0
(b) 2H2(g) + O2(g)  2H2O(l) [1]
(c) From the equation, mole ratio of H2 : O2 = 2 : 1
By Avogadro’s Law, volume ratio of H2 : O2 = 2 : 1
Volume of oxygen consumed =
4.80  103
dm3 = 2.40 × 103 dm3 [1]
2
Mole ratio of H2 : H2O = 1 : 1
Number of moles of water formed = 200 mol
Mass of water formed = 200 × (1.0 × 2 + 16.0) g = 3600 g [1]
Volume of water formed =
3600
cm3 = 3600 cm3 [1]
1 .0
32
(d) Volume of air required =
2.40  103
dm3 = 11 429 dm3 [1]
21%
10.
CH3CH2CH3(g) + 4O2(g)  CO2(g) + 2CO(g) + 4H2O(l) [1]
4.95
(ii) Number of moles of CH3CH2CH3(g) =
mol = 0.113 mol
12.0  3  1.0  8
(a) (i)
[1]
Mole ratio of CH3CH2CH3(g) to CO(g) is 1 : 2.
∴ number of moles of CO(g) = 2 × 0.113 mol = 0.226 mol [1]
Volume of CO(g) produced = 0.226 × 24.0 dm3 = 5.42 dm3 [1]
(b) 2CO(g) + O2(g)  2CO2(g) [1]
(c) (i) Mole ratio of CO(g) : O2(g) = 2 : 1
Number of moles of O2(g) =
0.226
mol = 0.113 mol [1]
2
Volume of O2(g) = 0.113 × 24.0 dm3 = 2.71 dm3 [1]
(ii) Mass of O2(g) = 16.0 × 2 × 0.113 g = 3.62 g [1]
11.
(a) Number of moles of magnesium hydroxide produced =
116.6
mol = 2.00 mol [1]
24.3  16.0  2  1.0  2
From the equation, the mole ratio of magnesium nitride to magnesium hydroxide
is 1 : 3.
Number of moles of magnesium nitride needed =
2.00
mol = 0.667 mol [1]
3
Mass of magnesium nitride = 0.667 × (24.3 × 3 + 14.0 × 2) g = 67.3 g [1]
(b) The mole ratio of magnesium nitride to ammonia is 1 : 2, so the number of moles
of ammonia = 0.667 × 2 mol = 1.33 mol [1]
Volume of ammonia = 1.33 × 24.0 dm3 = 31.9 dm3 [1]
(c) NH3(g) + HCl(aq)  NH4Cl(aq) [1]
The mole ratio of ammonia to hydrochloric acid is 1 : 1.
∴ number of moles of HCl needed = 1.33 mol [1]
Volume of 2.0 M HCl needed =
1.33
dm3 = 0.665 dm3 [1]
2.0
33