CBSE Class 12 Chemistry Chemical Kinetics Question Bank Set A

Read and download free pdf of CBSE Class 12 Chemistry Chemical Kinetics Question Bank Set A. Download printable Chemistry Class 12 Worksheets in pdf format, CBSE Class 12 Chemistry Unit 4 Chemical Kinetics Worksheet has been prepared as per the latest syllabus and exam pattern issued by CBSE, NCERT and KVS. Also download free pdf Chemistry Class 12 Assignments and practice them daily to get better marks in tests and exams for Class 12. Free chapter wise worksheets with answers have been designed by Class 12 teachers as per latest examination pattern

Unit 4 Chemical Kinetics Chemistry Worksheet for Class 12

Class 12 Chemistry students should refer to the following printable worksheet in Pdf in Class 12. This test paper with questions and solutions for Class 12 Chemistry will be very useful for tests and exams and help you to score better marks

Class 12 Chemistry Unit 4 Chemical Kinetics Worksheet Pdf

Question. For the reaction N2O5(g) → 2NO2(g) + 1/2O2(g) the value of rate of disappearance of N2O5 is given as 6.25 × 10–3 mol L–1s–1. The rate of formation of NO2 and O2 is given respectively as :
(a) 6.25 × 10–3 mol L–1 s–1 and 6.25 × 10–3 mol L–1 s–1
(b) 1.25 × 10–2 mol L–1 s–1 and 3.125 × 10–3 mol L–1 s–1
(c) 6.25 × 10–3 mol L–1 s–11 and 3.125 × 10–3 mol L–1 s–1
(d) 1.25 × 10–2 mol L–1 s–1 and 6.25 × 10–3 mol L–1 s–1
Answer. B

Question. Mechanism of a hypothetical reaction,
X2 + Y2 → 2XY, is given below :
(i) X2  → X + X (fast)
(ii) X + Y2  →  XY + Y (slow)
(iii) X + Y  → XY (fast)
The overall order of the reaction will be
(a) 2
(b) 0
(c) 1.5
(d) 1 
Answer. C

Question. The decomposition of phosphine (PH3) on tungsten at low pressure is a first-order reaction. It is because the
(a) rate is proportional to the surface coverage
(b) rate is inversely proportional to the surface coverage
(c) rate is independent of the surface coverage
(d) rate of decomposition is very slow
Answer. A

Question. The rate constant of the reaction A B is 0.6 × 10–3 mol L–1 s–1. If the concentration of A is 5 M, then concentration of B after 20 minutes is
(a) 3.60 M
(b) 0.36 M
(c) 0.72 M
(d) 1.08 M 
Answer. C

Question. For a reaction between A and B the order with respect to A is 2 and the order with respect to B is 3.The concentrations of both A and B are doubled, the rate will increase by a factor of
(a) 12
(b) 16
(c) 32
(d) 10
Answer. C

Question. In a reaction, A + B → product, rate is doubled when the concentration of B is doubled, and rate increases by a factor of 8 when the concentration of both the reactants (A and B) are doubled, rate law for the reaction can be written as
(a) rate = k[A][B]2
(b) rate = k[A]2[B]2
(c) rate = k[A][B]
(d) rate = k[A]2[B]
Answer. D

Question. Which one of the following statements for the order of a reaction is incorrect?
(a) Order can be determined only experimentally.
(b) Order is not influenced by stoichiometric coefficient of the reactants.
(c) Order of a reaction is sum of power to the concentration terms of reactants to express the rate of reaction.
(d) Order of reaction is always whole number.
Answer. D

Question. The unit of rate constant for a zero order reaction is
(a) mol L–1 s–1
(b) L mol–1 s–1
(c) L2 mol–2 s–1
(d) s–1
Answer. A

Question. For the reaction, A + B → products, it is observed that
(i) on doubling the initial concentration of A only, the rate of reaction is also doubled and
(ii) on doubling the initial concentration of both A and B, there is a change by a factor of 8 in the rate of the reaction.
The rate of this reaction is given by
(a) rate = k[A][B]2
(b) rate = k[A]2[B]2
(c) rate = k[A][B]
(d) rate = k[A]2[B]
Answer. A

Question. The reaction of hydrogen and iodine monochloride is given as :
H2(g) + 2ICl(g) → 2HCl(g) + I2(g)
This reaction is of first order with respect to H2(g) and ICl(g), following mechanisms were proposed.
Mechanism A :
H2(g) + 2ICl(g) → 2HCl(g) + I2(g)
Mechanism B :
H2(g) + ICl(g) → HCl(g) + HI(g) ; slow
HI(g) + ICl(g) → HCl(g)) + I2(g) ; fast
Which of the above mechanism(s) can be consistent with the given information about the reaction?
(a) A and B both
(b) Neither A nor B
(c) A only
(d) B only
Answer. D

Question. The rate of reaction between two reactants A and B decreases by a factor of 4 if the concentration of reactant B is doubled. The order of this reaction with respect to reactant B is
(a) 2
(b) –2
(c) 1
(d) –1 
Answer. B

Question. If the rate of the reaction is equal to the rate constant, the order of the reaction is
(a) 0
(b) 1
(c) 2
(d) 3 
Answer. A

Question. 2A → B + C, It would be a zero order reaction when
(a) the rate of reaction is proportional to square of concentration of A
(b) the rate of reaction remains same at any concentration of A
(c) the rate remains unchanged at any concentration of B and C
(d) the rate of reaction doubles if concentration of B is increased to double.
Answer. B

Question. For the reaction; 2N2O5 → 4NO2 + Orate and rate constant are 1.02 × 10–4 and 3.4 × 10–5 sec–1 respectively, then concentration of N2O5 at that time will be
(a) 1.732
(b) 3
(c) 1.02 × 10–4
(d) 3.4 × 105
Answer. B

Question. The given reaction, 2FeCl3 + SnCl2 → 2FeCl2 + SnCl4 is an example of
(a) third order reaction
(b) first order reaction
(c) second order reaction
(d) none of these. 
Answer. A

Question. The data for the reaction A + B → C, is
Exp.   [A]0       [B]0      Initial rate
1      0.012      0.035      0.10
2      0.024      0.070      0.80
3      0.024      0.035      0.10
4      0.012      0.070      0.80
The rate law corresponds to the above data is
(a) rate = k[A][B]3
(b) rate = k[A]2[B]2
(c) rate = k[B]3
(d) rate = k[B]4.
Answer. C

Question. The rate constant for a first order reaction is 4.606 × 10–3 s–1. The time required to reduce 2.0 g of the reactant to 0.2 g is
(a) 100 s
(b) 200 s
(c) 500 s
(d) 1000 s 
Answer. C

Question. If the rate constant for a first order reaction is k, the time (t) required for the completion of 99% of the reaction is given by
(a) t = 2.303/k
(b) t = 0.693/k
(c) t = 6.909/k
(d) t = 4.606/k
Answer. D

Question. A first order reaction has a rate constant of 2.303 × 10–3 s–1. The time required for 40 g of this reactant to reduce to 10 g will be [Given that log10 2 = 0.3010]
(a) 230.3 s
(b) 301 s
(c) 2000 s
(d) 602 s
Answer. D

Question. The correct difference between first and second order reactions is that
(a) the rate of a first-order reaction does not depend on reactant concentrations; the rate of a second-order reaction does depend on reactant concentrations
(b) the half-life of a first-order reaction does not depend on [A]0 ; the half-life of a second-order reaction does depend on [A]0
(c) a first-order reaction can be catalysed; a secondorder reaction cannot be catalysed
(d) the rate of a first-order reaction does depend on reactant concentrations; the rate of a secondorder reaction does not depend on reactant concentrations. 
Answer. B

Question. When initial concentration of the reactant is doubled, the half-life period of a zero order reaction
(a) is halved
(b) is doubled
(c) is tripled
(d) remains unchanged.
Answer. B

Question. A first order reaction has a specific reaction rate of 10–2 sec–1. How much time will it take for 20 g of the reactant to reduce to 5 g?
(a) 138.6 sec
(b) 346.5 sec
(c) 693.0 sec
(d) 238.6 sec 
Answer. A

Question. The rate of first-order reaction is 0.04 mol L–1 s–1 at 10 seconds and 0.03 mol L–1 s–1 at 20 seconds after initiation of the reaction. The half-life period of the reaction is
(a) 44.1 s
(b) 54.1 s
(c) 24.1 s
(d) 34.1 s 
Answer. C

Question. When initial concentration of a reactant is doubled in a reaction, its half-life period is not affected. The order of the reaction is
(a) second
(b) more than zero but less than first
(c) zero
(d) first. 
Answer. D

Question. A reaction is 50% complete in 2 hours and 75% complete in 4 hours. The order of reaction is
(a) 1
(b) 2
(c) 3
(d) 0
Answer. A

Question. The half-life of a substance in a certain enzymecatalysed reaction is 138 s. The time required for the concentration of the substance to fall from 1.28 mg L–1 to 0.04 mg L–1 is
(a) 414 s
(b) 552 s
(c) 690 s
(d) 276 s
Answer. C

Question. Half-life period of a first order reaction is 1386 seconds. The specific rate constant of the reaction is
(a) 0.5 × 10–2 s–1
(b) 0.5 × 10–3 s–1
(c) 5.0 × 10–2 s–1
(d) 5.0 × 10–3 s–1
Answer. B

Question. If 60% of a firstorder reaction was completed in 60 minutes, 50% of the same reaction would be completed in approximately (log 4 = 0.60, log 5 = 0.69)
(a) 45 minutes
(b) 60 minutes
(c) 40 minutes
(d) 50 minutes.
Answer. A

Question.For a first order reaction A → B the reaction rate at reactant concentration of 0.01 M is found to be 2.0 × 10–5 mol L–1 s–1. The half-life period of the reaction is
(a) 30 s
(b) 220 s
(c) 300 s
(d) 347 s
Answer. D

Question. The rate of a first order reaction is 1.5 × 10–2 mol L–1 min–1 at 0.5 M concentration of the reactant. The half-life of the reaction is
(a) 0.383 min
(b) 23.1 min
(c) 8.73 min
(d) 7.53 min
Answer. B

Question. The reaction A → B follows first order kinetics. The time taken for 0.8 mole of A to produce 0.6 mole of B is 1 hour. What is the time taken for conversion of 0.9 mole of A to produce 0.675 mole of B ?
(a) 1 hour
(b) 0.5 hour
(c) 0.25 hour
(d) 2 hours
Answer. A

Question. For a first-order reaction, the half-life period is independent of
(a) first power of final concentration
(b) cube root of initial concentration
(c) initial concentration
(d) square root of final concentration
Answer. C

Question. For a reaction, activation energy Ea = 0 and the rate constant at 200 K is 1.6 × 106 s–1. The rate constant at 400 K will be [Given that gas constant R = 8.314 J K–1 mol–1]
(a) 3.2 × 104 s–1
(b) 1.6 × 10s–1
(c) 1.6 × 103 s–1
(d) 3.2 × 106 s–1
Answer. B

Question. The addition of a catalyst during a chemical reaction alters which of the following quantities?
(a) Enthalpy
(b) Activation energy
(c) Entropy
(d) Internal energy
Answer. B

Question. What is the activation energy for a reaction if its rate doubles when the temperature is raised from 20 °C to 35 °C? (R = 8.314 J mol–1 K–1)
(a) 34.7 kJ mol–1
(b) 15.1 kJ mol–1
(c) 342 kJ mol–1
(d) 269 kJ mol–1
Answer. A

Question. In a zero-order reaction, for every 10 °C rise of temperature, the rate is doubled. If the temperature is increased from 10 °C to 100 °C, the rate of the reaction will become
(a) 256 times
(b) 512 times
(c) 64 times
(d) 128 times.
Answer. B

Question. The rate of the reaction,
2NO + Cl2 → 2NOCl is given by the rate equation, rate = k[NO]2[Cl2]. The value of the rate constant can be increased by
(a) increasing the temperature
(b) increasing the concentration of NO
(c) increasing the concentration of the Cl2
(d) doing all of these.
Answer. A

Question. The activation energy for a simple chemical reaction A ⇔ B is Ea in forward direction. The activation energy for reverse reaction
(a) is negative of Ea
(b) is always less than Ea
(c) can be less than or more than Ea
(d) is always double of Ea
Answer. C

Question. When a biochemical reaction is carried out in laboratory, outside the human body in absence of enzyme, then rate of reaction obtained is 10–6 times, the activation energy of reaction in the presence of enzyme is
(a) 6/RT
(b) P is required
(c) different from Ea obtained in laboratory
(d) can’t say anything.
Answer. A

Question. How enzymes increases the rate of reactions?
(a) By lowering activation energy
(b) By increasing activation energy
(c) By changing equilibrium constant
(d) By forming enzyme substrate complex
Answer. A

Question. Activation energy of a chemical reaction can be determined by
(a) evaluating rate constants at two different temperatures
(b) evaluating velocities of reaction at two different temperatures
(c) evaluating rate constant at standard temperature
(d) changing concentration of reactants. 
Answer. A

Question. By the action of enzymes, the rate of biochemical reaction
(a) does not change
(b) increases
(c) decreases
(d) either (a) or (c).
Answer. B

Question. An increase in the concentration of the reactants of a reaction leads to change in
(a) activation energy
(b) heat of reaction
(c) threshold energy
(d) collision frequency.
Answer. D

 

 
VSA QUESTIONS (1 - MARK QUESTIONS)
 
1. Why does the rate of a reaction not remain constant throughout the reaction process?
 
2. What is meant by order of a reaction being zero?
 
3. What is the shape of graph between log k vs1/T. What is the relationship between its slope and activation energy (Ea) ?
 
4. For a chemical reaction rate constant k = 5.3 × 10–4mol L–1 s–1.what will be the order of the reaction?
 
5. Express the rate of reaction in terms of disappearance of hydrogen and appearance of ammonia in the given reaction. N2(g) + 3 H2 (g)→ 2NH3 (g)
 
6. For the elementary step of a chemical reaction : A + H2O → Brate = [A]1. What is the molecularity and order of the reaction.
 
7. Mention one example of pseudo first order reaction.
 
8. For the reaction Cl2(g)+NO (g) → 2NOCl(g),the rate law is expressed as rate =k[Cl2] [NO]2. What is the overall order of this reaction?
 
SA (I) QUESTIONS (2 - MARK QUESTIONS)
 
9. What do you mean by the rate law and rate constant of a reaction? Identify the order of a reaction if the units of its rate constant are
i. L-1mol s-1
ii. Lmol-1
 
10. A reaction is second order with respect to a reactant A. How is the rate of this reaction altered if the concentration of A is
i. Doubled
ii. Reduced to half?
 
11. Explain the terms
i. Rate determining step of areaction
ii. Molecularity of a reaction
 
12. iii. The rate constant for a reaction of zero order in A is 0.0030 mol L-1s-1. How long will it take for the initial concentration of A to fall from 0.10M to 0.075 M?
 
13. A first order reaction takes 40 minutes for 30% decomposition. Calculate its t1/2 value.
 
14. Show that for a first order reaction,the time required for half life is independent of initial concentration.
 
15. A reactant has a half life of 10 minutes.
i. Calculate the rate constant for the first order reaction.
ii. What fraction of the reactant will be left after an hour of the reaction has occurred?
 
16. Calculate the rate constant of a reaction at 293 K, given that:
Ea=103 KJ/Mol, k=7.87x 10-7s-1, at 273 K,R=8.314 JK-1mol-1
 
17. The graphs (1 and 2) given below are plots of rate of reaction verses concentration of the reaction. Predict the order from the graphs

CBSE Class 12 Chemistry Chemical Kinetics Question Bank Set A 1

 

SA (II) QUESTIONS (3- MARK QUESTIONS)

17. For a decomposition reaction, the values of rate constant k , at two different temperatures are given below.
K1=2.15x10-8Lmol-1s-1 at 650 K , K2=2.39 x10-7Lmol-1s-1 at 700 K
Calculate the value of activation energy for this reaction R=8.314JK-1mol-1
 
18. Consider the reaction 2A+B → C+ D
Following results were obtained in experiments designed to study the rate of reaction.
 
CBSE Class 12 Chemistry Chemical Kinetics Question Bank Set A 2
 
i. Write the rate law for the reaction.
ii. Calculate the value of rate constant for the reaction
iii. Which of the following possible reaction mechanisms is constant with the rate law found in (i)
 
I. A+B → C+ E (slow) A+E → D (fast)
II. B → C+ E (slow) A+E→ F (fast)
A+F→ D (fast)
 
19.. Explain the following :
i. A lump of coal burns at moderate rate in air while coal dust burns explosively.
ii. Average rate of reaction does not give the true picture of the reaction.
iii. Reactions of high molecularity are less in number.
 
20. i. Write four points of difference between order and molecularity of a reaction.
ii. List four methods for determination of order of reactions?
 
21. The decomposition of PH3 proceeds according to the following equation.
4PH3(g) → P4(g)+6 H2(g)
It is found that the reaction follows the following rate equation, Rate =k [PH3].The half life of PH3 is 37.9 s at 120 oC.
i. How much time is required for ¾ th of PH3 to decompose?
ii. What fraction of the original sample of PHremains behind after 1 minute?
 
LONG ANSWER QUESTION (5- MARK QUESTION)
 
22. i. Defineelementary reaction in a process.
ii. State the role of activated complex in a reaction and state its relation with activation energy.
iii. H2O2 (aq) decomposes to H2O(l) and O2 (g) in a reaction that is of first order in H2O2 and has a rate constant K=1.06 x10-3min -1.
a) How long will it take 15% of a sample of H2O2 to decompose?
b) How long will it take 85% of a sample of H2O2 to decompose?

 

Please click on below link to download CBSE Class 12 Chemistry Chemical Kinetics Question Bank Set A

Unit 4 Chemical Kinetics CBSE Class 12 Chemistry Worksheet

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