A. Very-Short-Answer Questions
1. What is the unit of the rate of a
reaction?
2. How is the order of a reaction
related to its stoichiometry?
3. If rate = k[A][B]2 for a reaction, what is
the order of the reaction?
4. What are the units for the rate constants of
zero order and first-order reactions?
5. What is the order of reaction if the rate
constant is 1.35x10-2 mol-2 L2s-1?
6. On what factor does the rate constant of a
reaction depends?
7. What is the half-life of a reaction?
8. How is the half-life related to the initial
concentration of the reactant for a (i) zero-order reaction, (ii) first-order
reaction?
9. The enthalpy of a reaction is 50 kJ. What is
the minimum value of the activation energy for the reaction?
10. How does the rate of a zero-order reaction
change with time?
B. Short-Answer Questions
1. What do you understand by the rate of a
chemical with time?
2. What is the difference between average rate
and instantaneous rate?
3. On what factor does the rate of reaction
depend?
4. What is the rate law?
5. What is the rate constant?
6. The rate constant of a reaction is 75s-1.
What will be the rate constant if the unit of time is the minute?
7. Draw graphs to show the change in the
concentration of the reactant with time for a
(i) zero-order reaction (ii) first-order reaction.
(i) zero-order reaction (ii) first-order reaction.
8. For a zero-order reaction, how does the length
of the first half-life compare with the length of the second half-life?
9. Why do gaseous decomposition reactions on
metal surfaces follow zero-order kinetics in the beginning but change to
first-order later?
10. What
is a pseudo-first-order reaction?
11. For a reaction, rate = k[A]2/[B]. What will happen to the rate if the concentration of
(i)
A is doubled,
(ii)
B is doubled,
(iii)
Both A and B are doubled?
12. What
do you understand by the mechanism of a reaction?
13. What
do you understand by the rate-determining step?
14. What
is the molecularity of a reaction?
15. What
is activation energy?
16. Why
does the rate of reaction increase with a rise in temperature?
17. What
is the Arrhenius equation?
18. What
is the significance of the pre-exponential factor in the Arrhenius equation?
19. How does a catalyst increase the rate of a
reaction?
20. Why is it not possible for a catalysed
reaction to occur in a single step?
21. What is a transition state?
22. What is a reaction intermediate?
C. Long-Answer Question
1. The reaction A+B → C+D is believed to occur in two steps:
Step 1 (fast): A+B → E
Step 2 (slow): E → C+D
(i)
Which is the
rate-determining step?
(ii)
What is the rate
molecularity of the rate-determining step?
(iii)
What is the order
if the reaction?
2. The reaction mechanism for a reaction is as
follows.
Step 1 (slow): O3(g) + NO3(g)
→
NO3(g) + O2(g)
Step 2 (fast): NO3(g) + NO2(g) → N2O5(g)
(i)
Write the overall
reaction.
(ii)
Identify the
molecularity of each step.
(iii)
Identify the
reactants, products, catalysts and reaction intermediates (whichever apply).
(iv)
What is the rate
law expression for this mechanism?
3. The reaction mechanism for a reaction is as
follows.
Step 1 (slow): Cl(g) + O3(g) → ClO(g) + O2(g)
Step 2 (fast): ClO(g) + O2 → Cl(g) + O2(g)
(i)
Write the overall
reaction.
(ii)
Identify the
molecularity of each step.
(iii)
Identify the
reactants, products, catalysts and reaction intermediates (whichever apply)
(iv)
What is the rate
law expression for this mechanism?
4. The reaction mechanism for a reaction is as
follows.
Step 1 (slow): 2NO(g) + O2(g) → 2NO2(g)
Step 2 (fast): 2[NO2(g) + SO2(g)
→ NO(g) + SO3(g)]
(i)
What is the
overall reaction?
(ii)
Identify the
molecularity of each step.
(iii)
Identify the
reactants, products, catalysts and reaction intermediates(whichever apply).
(iv)
What is the rate
law expression for this mechanism?
5. The reaction mechanism for a reaction is as
follows.
Step 1 (fast eq.): 2NO(g) → N2O2(g)
Step 2 (fast eq.): N2O2(g)
+ H2(g) → N2O(g) +
H2O(g)
Step 3 (slow): N20(g) + H2(g) → N2(g) + H2
(i)
What is the
overall reaction?
(ii)
Identify the
molecularity of each step.
(iii)
Identify the
reactants, products, catalysts and reaction intermediates
(iv)
What is the rate
law expression?
6. The reaction for a mechanism is as follows.
Step 1 (fast eq.): I2(g) → 2I(g)
Step 2 (fast eq.): H2(g) + I(g) → H2I(g)
Step 3 (slow): H2I(g) + I(g) → 2HI(g)
(i)
What is the
overall reaction?
(ii)
Identify the
molecularity of each step.
(iii)
Identify the
reactants, products, catalysts and reaction intermediates
(iv)
What is the rate
law expression?
7. In acidic solution, the breakdown of sucrose
into glucose and fructose has the rate law:
rate = k[H+] [sucrose]. The initial rate of sucrose breakdown is measured in a solution that is 0.010 M H+, 0.10 M fructose, and 0.01 M glucose. How does the rate change if
rate = k[H+] [sucrose]. The initial rate of sucrose breakdown is measured in a solution that is 0.010 M H+, 0.10 M fructose, and 0.01 M glucose. How does the rate change if
(a) The concentration of sucrose is changed to 2.5
M?
(b) The concentrations of sucrose, fructose, and
glucose are all changed to 0.50 M?
(c) The concentration of H+ is changed
to 0.00010 M?
(d) The concentration of sucrose and H+
are each changed to 0.10 M?
8. The following data were obtained in the study
of a first-order reaction for the decomposition of A to form products.
[A](M)
|
1.00
|
0.80
|
0.60
|
0.35
|
0.15
|
Time(sec)
|
0
|
110
|
255
|
525
|
950
|
(a) What you must plot to show that this reaction
follows first-order kinetics?
(b) If a suitable plot is made using given data
and a straight line with
slope = -2.0x10-3 is obtained, what are the value and unit of k for this reaction?
slope = -2.0x10-3 is obtained, what are the value and unit of k for this reaction?
9. In order to determine the order of the
reaction A + B → C, a student determined the rates at different initial
concentrations. His / Her data are tabulated below. Comment on his / her
effort.
[A] (mol/L)
|
[B] (mol/L)
|
Rate of formation of C (mol/L s)
|
0.03
|
0.03
|
3x10-5
|
0.06
|
0.06
|
1.2x10-4
|
0.09
|
0.09
|
2.7x10-4
|
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