Chemical Kinetics Practice

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NEET Chemistry - Chapter 9

Chemical Kinetics Practice Tests

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Rate basics
1. Rate of reaction is the change in concentration of reactant or product per:
- A. unit time (Correct)
- B. unit pressure
- C. unit mass
- D. unit temperature
Explanation: Rate measures how fast concentration changes.
Average rate
2. Average rate over a time interval uses:
- A. change in concentration divided by time interval (Correct)
- B. final concentration only
- C. activation energy only
- D. equilibrium constant
Explanation: It is a finite-time rate measure.
Instantaneous rate
3. Instantaneous rate corresponds to the slope of concentration-time curve at a:
- A. particular instant (Correct)
- B. whole interval
- C. end point only
- D. midpoint only
Explanation: It is the tangent slope at that point.
Rate law
4. The rate law expresses rate as a function of:
- A. reactant concentrations raised to powers (Correct)
- B. product color only
- C. temperature alone
- D. equilibrium constant only
Explanation: Orders are determined experimentally.
Order
5. Overall order of reaction equals:
- A. sum of exponents in rate law (Correct)
- B. stoichiometric sum always
- C. difference of coefficients
- D. activation energy
Explanation: Order is obtained by adding the powers in the rate expression.
Molecularity
6. Molecularity refers to number of species colliding in an:
- A. elementary step (Correct)
- B. overall complex reaction
- C. equilibrium state
- D. catalyst surface
Explanation: Molecularity is defined only for elementary steps.
Order vs molecularity
7. Order of a reaction may be zero, fractional, or integral, while molecularity is:
- A. always a positive integer (Correct)
- B. always fractional
- C. always zero
- D. negative sometimes
Explanation: Molecularity counts discrete colliding species.
Zero order
8. For a zero-order reaction, rate is:
- A. independent of reactant concentration (Correct)
- B. directly proportional to concentration
- C. inversely proportional to concentration
- D. always zero
Explanation: The rate remains constant until reactant is exhausted enough.
First order
9. For a first-order reaction, rate is proportional to:
- A. first power of concentration (Correct)
- B. square of concentration
- C. cube of concentration
- D. pressure alone
Explanation: That is the defining rate law.
Second order
10. For a second-order reaction in one reactant A, rate is proportional to:
- A. $[A]^2$ (Correct)
- B. $[A]$
- C. $1/[A]$
- D. $[A]^0$
Explanation: Second-order dependence means square relation.
Units
11. Units of first-order rate constant are:
- A. s$^{-1}$ (Correct)
- B. mol L$^{-1}$ s$^{-1}$
- C. L mol$^{-1}$ s$^{-1}$
- D. mol$^{-2}$ L$^2$ s$^{-1}$
Explanation: First-order constant has dimension of inverse time.
Units
12. Units of second-order rate constant are:
- A. L mol$^{-1}$ s$^{-1}$ (Correct)
- B. s$^{-1}$
- C. mol L$^{-1}$ s$^{-1}$
- D. L$^2$ mol$^{-2}$ s$^{-1}$ only
Explanation: Second-order rate constant carries inverse concentration and time.
Half-life
13. For a first-order reaction, half-life is:
- A. independent of initial concentration (Correct)
- B. directly proportional to initial concentration
- C. inversely proportional to initial concentration
- D. zero
Explanation: This is a signature property of first-order kinetics.
Half-life
14. For a zero-order reaction, half-life is:
- A. directly proportional to initial concentration (Correct)
- B. independent of initial concentration
- C. inversely proportional to initial concentration
- D. infinite
Explanation: $t_{1/2}=[A]_0/2k$.
Integrated law
15. Integrated rate law for first-order reaction is:
- A. $k=\frac{2.303}{t}\log\frac{[A]_0}{[A]}$ (Correct)
- B. $[A]=[A]_0-kt$
- C. $1/[A]=1/[A]_0+kt$
- D. $\pi=CRT$
Explanation: This is the standard first-order integrated equation.
Integrated law
16. Integrated rate law for zero-order reaction is:
- A. $[A]=[A]_0-kt$ (Correct)
- B. $\log[A]=\log[A]_0-kt/2.303$
- C. $1/[A]=1/[A]_0+kt$
- D. $k=2.303/t$
Explanation: Concentration falls linearly with time in zero-order reactions.
Integrated law
17. Integrated rate law for a second-order reaction in A is:
- A. $1/[A]=1/[A]_0+kt$ (Correct)
- B. $[A]=[A]_0-kt$
- C. $\log[A]=\log[A]_0-kt$
- D. $\Delta G=\Delta H-T\Delta S$
Explanation: This is the standard second-order integrated form.
Arrhenius
18. Arrhenius equation relates rate constant to:
- A. temperature and activation energy (Correct)
- B. pressure and volume
- C. mass and density
- D. pH and ionic strength
Explanation: It explains exponential temperature dependence.
Activation energy
19. Activation energy is the minimum energy needed for:
- A. effective collision (Correct)
- B. equilibrium
- C. phase change
- D. adsorption
Explanation: Only sufficiently energetic collisions can react.
Catalyst
20. A catalyst speeds up a reaction by:
- A. lowering activation energy (Correct)
- B. increasing enthalpy change
- C. changing equilibrium constant
- D. raising molecularity
Explanation: It offers an alternate lower-energy pathway.
Collision theory
21. According to collision theory, effective collisions require proper orientation and sufficient:
- A. energy (Correct)
- B. volume
- C. color
- D. mass
Explanation: Both conditions are needed for reaction.
Pseudo-first order
22. If one reactant is taken in large excess, a higher-order reaction may appear:
- A. pseudo-first order (Correct)
- B. zero order always
- C. third order always
- D. orderless
Explanation: The excess concentration stays nearly constant.
Radioactivity analogy
23. A process often following first-order kinetics is:
- A. radioactive decay (Correct)
- B. surface tension
- C. osmosis only
- D. simple melting
Explanation: Its rate is proportional to the amount remaining.
Graph
24. A straight line for zero-order kinetics is obtained by plotting:
- A. $[A]$ vs t (Correct)
- B. $\log[A]$ vs t
- C. $1/[A]$ vs t
- D. rate vs 1/[A]$
Explanation: Zero-order concentration falls linearly with time.
Graph
25. A straight line for first-order kinetics is obtained by plotting:
- A. $\log[A]$ vs t (Correct)
- B. $[A]$ vs t
- C. $1/[A]$ vs t
- D. k vs t
Explanation: The integrated first-order law is logarithmic.
Rate basics
26. Rate of reaction is the change in concentration of reactant or product per:
- A. unit time (Correct)
- B. unit pressure
- C. unit mass
- D. unit temperature
Explanation: Rate measures how fast concentration changes.
Average rate
27. Average rate over a time interval uses:
- A. change in concentration divided by time interval (Correct)
- B. final concentration only
- C. activation energy only
- D. equilibrium constant
Explanation: It is a finite-time rate measure.
Instantaneous rate
28. Instantaneous rate corresponds to the slope of concentration-time curve at a:
- A. particular instant (Correct)
- B. whole interval
- C. end point only
- D. midpoint only
Explanation: It is the tangent slope at that point.
Rate law
29. The rate law expresses rate as a function of:
- A. reactant concentrations raised to powers (Correct)
- B. product color only
- C. temperature alone
- D. equilibrium constant only
Explanation: Orders are determined experimentally.
Order
30. Overall order of reaction equals:
- A. sum of exponents in rate law (Correct)
- B. stoichiometric sum always
- C. difference of coefficients
- D. activation energy
Explanation: Order is obtained by adding the powers in the rate expression.
Molecularity
31. Molecularity refers to number of species colliding in an:
- A. elementary step (Correct)
- B. overall complex reaction
- C. equilibrium state
- D. catalyst surface
Explanation: Molecularity is defined only for elementary steps.
Order vs molecularity
32. Order of a reaction may be zero, fractional, or integral, while molecularity is:
- A. always a positive integer (Correct)
- B. always fractional
- C. always zero
- D. negative sometimes
Explanation: Molecularity counts discrete colliding species.
Zero order
33. For a zero-order reaction, rate is:
- A. independent of reactant concentration (Correct)
- B. directly proportional to concentration
- C. inversely proportional to concentration
- D. always zero
Explanation: The rate remains constant until reactant is exhausted enough.
First order
34. For a first-order reaction, rate is proportional to:
- A. first power of concentration (Correct)
- B. square of concentration
- C. cube of concentration
- D. pressure alone
Explanation: That is the defining rate law.
Second order
35. For a second-order reaction in one reactant A, rate is proportional to:
- A. $[A]^2$ (Correct)
- B. $[A]$
- C. $1/[A]$
- D. $[A]^0$
Explanation: Second-order dependence means square relation.
Units
36. Units of first-order rate constant are:
- A. s$^{-1}$ (Correct)
- B. mol L$^{-1}$ s$^{-1}$
- C. L mol$^{-1}$ s$^{-1}$
- D. mol$^{-2}$ L$^2$ s$^{-1}$
Explanation: First-order constant has dimension of inverse time.
Units
37. Units of second-order rate constant are:
- A. L mol$^{-1}$ s$^{-1}$ (Correct)
- B. s$^{-1}$
- C. mol L$^{-1}$ s$^{-1}$
- D. L$^2$ mol$^{-2}$ s$^{-1}$ only
Explanation: Second-order rate constant carries inverse concentration and time.
Half-life
38. For a first-order reaction, half-life is:
- A. independent of initial concentration (Correct)
- B. directly proportional to initial concentration
- C. inversely proportional to initial concentration
- D. zero
Explanation: This is a signature property of first-order kinetics.
Half-life
39. For a zero-order reaction, half-life is:
- A. directly proportional to initial concentration (Correct)
- B. independent of initial concentration
- C. inversely proportional to initial concentration
- D. infinite
Explanation: $t_{1/2}=[A]_0/2k$.
Integrated law
40. Integrated rate law for first-order reaction is:
- A. $k=\frac{2.303}{t}\log\frac{[A]_0}{[A]}$ (Correct)
- B. $[A]=[A]_0-kt$
- C. $1/[A]=1/[A]_0+kt$
- D. $\pi=CRT$
Explanation: This is the standard first-order integrated equation.
Integrated law
41. Integrated rate law for zero-order reaction is:
- A. $[A]=[A]_0-kt$ (Correct)
- B. $\log[A]=\log[A]_0-kt/2.303$
- C. $1/[A]=1/[A]_0+kt$
- D. $k=2.303/t$
Explanation: Concentration falls linearly with time in zero-order reactions.
Integrated law
42. Integrated rate law for a second-order reaction in A is:
- A. $1/[A]=1/[A]_0+kt$ (Correct)
- B. $[A]=[A]_0-kt$
- C. $\log[A]=\log[A]_0-kt$
- D. $\Delta G=\Delta H-T\Delta S$
Explanation: This is the standard second-order integrated form.
Arrhenius
43. Arrhenius equation relates rate constant to:
- A. temperature and activation energy (Correct)
- B. pressure and volume
- C. mass and density
- D. pH and ionic strength
Explanation: It explains exponential temperature dependence.
Activation energy
44. Activation energy is the minimum energy needed for:
- A. effective collision (Correct)
- B. equilibrium
- C. phase change
- D. adsorption
Explanation: Only sufficiently energetic collisions can react.
Catalyst
45. A catalyst speeds up a reaction by:
- A. lowering activation energy (Correct)
- B. increasing enthalpy change
- C. changing equilibrium constant
- D. raising molecularity
Explanation: It offers an alternate lower-energy pathway.
Collision theory
46. According to collision theory, effective collisions require proper orientation and sufficient:
- A. energy (Correct)
- B. volume
- C. color
- D. mass
Explanation: Both conditions are needed for reaction.
Pseudo-first order
47. If one reactant is taken in large excess, a higher-order reaction may appear:
- A. pseudo-first order (Correct)
- B. zero order always
- C. third order always
- D. orderless
Explanation: The excess concentration stays nearly constant.
Radioactivity analogy
48. A process often following first-order kinetics is:
- A. radioactive decay (Correct)
- B. surface tension
- C. osmosis only
- D. simple melting
Explanation: Its rate is proportional to the amount remaining.
Graph
49. A straight line for zero-order kinetics is obtained by plotting:
- A. $[A]$ vs t (Correct)
- B. $\log[A]$ vs t
- C. $1/[A]$ vs t
- D. rate vs 1/[A]$
Explanation: Zero-order concentration falls linearly with time.
Graph
50. A straight line for first-order kinetics is obtained by plotting:
- A. $\log[A]$ vs t (Correct)
- B. $[A]$ vs t
- C. $1/[A]$ vs t
- D. k vs t
Explanation: The integrated first-order law is logarithmic.
Rate basics
51. Rate of reaction is the change in concentration of reactant or product per:
- A. unit time (Correct)
- B. unit pressure
- C. unit mass
- D. unit temperature
Explanation: Rate measures how fast concentration changes.
Average rate
52. Average rate over a time interval uses:
- A. change in concentration divided by time interval (Correct)
- B. final concentration only
- C. activation energy only
- D. equilibrium constant
Explanation: It is a finite-time rate measure.
Instantaneous rate
53. Instantaneous rate corresponds to the slope of concentration-time curve at a:
- A. particular instant (Correct)
- B. whole interval
- C. end point only
- D. midpoint only
Explanation: It is the tangent slope at that point.
Rate law
54. The rate law expresses rate as a function of:
- A. reactant concentrations raised to powers (Correct)
- B. product color only
- C. temperature alone
- D. equilibrium constant only
Explanation: Orders are determined experimentally.
Order
55. Overall order of reaction equals:
- A. sum of exponents in rate law (Correct)
- B. stoichiometric sum always
- C. difference of coefficients
- D. activation energy
Explanation: Order is obtained by adding the powers in the rate expression.
Molecularity
56. Molecularity refers to number of species colliding in an:
- A. elementary step (Correct)
- B. overall complex reaction
- C. equilibrium state
- D. catalyst surface
Explanation: Molecularity is defined only for elementary steps.
Order vs molecularity
57. Order of a reaction may be zero, fractional, or integral, while molecularity is:
- A. always a positive integer (Correct)
- B. always fractional
- C. always zero
- D. negative sometimes
Explanation: Molecularity counts discrete colliding species.
Zero order
58. For a zero-order reaction, rate is:
- A. independent of reactant concentration (Correct)
- B. directly proportional to concentration
- C. inversely proportional to concentration
- D. always zero
Explanation: The rate remains constant until reactant is exhausted enough.
First order
59. For a first-order reaction, rate is proportional to:
- A. first power of concentration (Correct)
- B. square of concentration
- C. cube of concentration
- D. pressure alone
Explanation: That is the defining rate law.
Second order
60. For a second-order reaction in one reactant A, rate is proportional to:
- A. $[A]^2$ (Correct)
- B. $[A]$
- C. $1/[A]$
- D. $[A]^0$
Explanation: Second-order dependence means square relation.
Units
61. Units of first-order rate constant are:
- A. s$^{-1}$ (Correct)
- B. mol L$^{-1}$ s$^{-1}$
- C. L mol$^{-1}$ s$^{-1}$
- D. mol$^{-2}$ L$^2$ s$^{-1}$
Explanation: First-order constant has dimension of inverse time.
Units
62. Units of second-order rate constant are:
- A. L mol$^{-1}$ s$^{-1}$ (Correct)
- B. s$^{-1}$
- C. mol L$^{-1}$ s$^{-1}$
- D. L$^2$ mol$^{-2}$ s$^{-1}$ only
Explanation: Second-order rate constant carries inverse concentration and time.
Half-life
63. For a first-order reaction, half-life is:
- A. independent of initial concentration (Correct)
- B. directly proportional to initial concentration
- C. inversely proportional to initial concentration
- D. zero
Explanation: This is a signature property of first-order kinetics.
Half-life
64. For a zero-order reaction, half-life is:
- A. directly proportional to initial concentration (Correct)
- B. independent of initial concentration
- C. inversely proportional to initial concentration
- D. infinite
Explanation: $t_{1/2}=[A]_0/2k$.
Integrated law
65. Integrated rate law for first-order reaction is:
- A. $k=\frac{2.303}{t}\log\frac{[A]_0}{[A]}$ (Correct)
- B. $[A]=[A]_0-kt$
- C. $1/[A]=1/[A]_0+kt$
- D. $\pi=CRT$
Explanation: This is the standard first-order integrated equation.
Integrated law
66. Integrated rate law for zero-order reaction is:
- A. $[A]=[A]_0-kt$ (Correct)
- B. $\log[A]=\log[A]_0-kt/2.303$
- C. $1/[A]=1/[A]_0+kt$
- D. $k=2.303/t$
Explanation: Concentration falls linearly with time in zero-order reactions.
Integrated law
67. Integrated rate law for a second-order reaction in A is:
- A. $1/[A]=1/[A]_0+kt$ (Correct)
- B. $[A]=[A]_0-kt$
- C. $\log[A]=\log[A]_0-kt$
- D. $\Delta G=\Delta H-T\Delta S$
Explanation: This is the standard second-order integrated form.
Arrhenius
68. Arrhenius equation relates rate constant to:
- A. temperature and activation energy (Correct)
- B. pressure and volume
- C. mass and density
- D. pH and ionic strength
Explanation: It explains exponential temperature dependence.
Activation energy
69. Activation energy is the minimum energy needed for:
- A. effective collision (Correct)
- B. equilibrium
- C. phase change
- D. adsorption
Explanation: Only sufficiently energetic collisions can react.
Catalyst
70. A catalyst speeds up a reaction by:
- A. lowering activation energy (Correct)
- B. increasing enthalpy change
- C. changing equilibrium constant
- D. raising molecularity
Explanation: It offers an alternate lower-energy pathway.
Collision theory
71. According to collision theory, effective collisions require proper orientation and sufficient:
- A. energy (Correct)
- B. volume
- C. color
- D. mass
Explanation: Both conditions are needed for reaction.
Pseudo-first order
72. If one reactant is taken in large excess, a higher-order reaction may appear:
- A. pseudo-first order (Correct)
- B. zero order always
- C. third order always
- D. orderless
Explanation: The excess concentration stays nearly constant.
Radioactivity analogy
73. A process often following first-order kinetics is:
- A. radioactive decay (Correct)
- B. surface tension
- C. osmosis only
- D. simple melting
Explanation: Its rate is proportional to the amount remaining.
Graph
74. A straight line for zero-order kinetics is obtained by plotting:
- A. $[A]$ vs t (Correct)
- B. $\log[A]$ vs t
- C. $1/[A]$ vs t
- D. rate vs 1/[A]$
Explanation: Zero-order concentration falls linearly with time.
Graph
75. A straight line for first-order kinetics is obtained by plotting:
- A. $\log[A]$ vs t (Correct)
- B. $[A]$ vs t
- C. $1/[A]$ vs t
- D. k vs t
Explanation: The integrated first-order law is logarithmic.
Rate basics
76. Rate of reaction is the change in concentration of reactant or product per:
- A. unit time (Correct)
- B. unit pressure
- C. unit mass
- D. unit temperature
Explanation: Rate measures how fast concentration changes.
Average rate
77. Average rate over a time interval uses:
- A. change in concentration divided by time interval (Correct)
- B. final concentration only
- C. activation energy only
- D. equilibrium constant
Explanation: It is a finite-time rate measure.
Instantaneous rate
78. Instantaneous rate corresponds to the slope of concentration-time curve at a:
- A. particular instant (Correct)
- B. whole interval
- C. end point only
- D. midpoint only
Explanation: It is the tangent slope at that point.
Rate law
79. The rate law expresses rate as a function of:
- A. reactant concentrations raised to powers (Correct)
- B. product color only
- C. temperature alone
- D. equilibrium constant only
Explanation: Orders are determined experimentally.
Order
80. Overall order of reaction equals:
- A. sum of exponents in rate law (Correct)
- B. stoichiometric sum always
- C. difference of coefficients
- D. activation energy
Explanation: Order is obtained by adding the powers in the rate expression.
Molecularity
81. Molecularity refers to number of species colliding in an:
- A. elementary step (Correct)
- B. overall complex reaction
- C. equilibrium state
- D. catalyst surface
Explanation: Molecularity is defined only for elementary steps.
Order vs molecularity
82. Order of a reaction may be zero, fractional, or integral, while molecularity is:
- A. always a positive integer (Correct)
- B. always fractional
- C. always zero
- D. negative sometimes
Explanation: Molecularity counts discrete colliding species.
Zero order
83. For a zero-order reaction, rate is:
- A. independent of reactant concentration (Correct)
- B. directly proportional to concentration
- C. inversely proportional to concentration
- D. always zero
Explanation: The rate remains constant until reactant is exhausted enough.
First order
84. For a first-order reaction, rate is proportional to:
- A. first power of concentration (Correct)
- B. square of concentration
- C. cube of concentration
- D. pressure alone
Explanation: That is the defining rate law.
Second order
85. For a second-order reaction in one reactant A, rate is proportional to:
- A. $[A]^2$ (Correct)
- B. $[A]$
- C. $1/[A]$
- D. $[A]^0$
Explanation: Second-order dependence means square relation.
Units
86. Units of first-order rate constant are:
- A. s$^{-1}$ (Correct)
- B. mol L$^{-1}$ s$^{-1}$
- C. L mol$^{-1}$ s$^{-1}$
- D. mol$^{-2}$ L$^2$ s$^{-1}$
Explanation: First-order constant has dimension of inverse time.
Units
87. Units of second-order rate constant are:
- A. L mol$^{-1}$ s$^{-1}$ (Correct)
- B. s$^{-1}$
- C. mol L$^{-1}$ s$^{-1}$
- D. L$^2$ mol$^{-2}$ s$^{-1}$ only
Explanation: Second-order rate constant carries inverse concentration and time.
Half-life
88. For a first-order reaction, half-life is:
- A. independent of initial concentration (Correct)
- B. directly proportional to initial concentration
- C. inversely proportional to initial concentration
- D. zero
Explanation: This is a signature property of first-order kinetics.
Half-life
89. For a zero-order reaction, half-life is:
- A. directly proportional to initial concentration (Correct)
- B. independent of initial concentration
- C. inversely proportional to initial concentration
- D. infinite
Explanation: $t_{1/2}=[A]_0/2k$.
Integrated law
90. Integrated rate law for first-order reaction is:
- A. $k=\frac{2.303}{t}\log\frac{[A]_0}{[A]}$ (Correct)
- B. $[A]=[A]_0-kt$
- C. $1/[A]=1/[A]_0+kt$
- D. $\pi=CRT$
Explanation: This is the standard first-order integrated equation.
Integrated law
91. Integrated rate law for zero-order reaction is:
- A. $[A]=[A]_0-kt$ (Correct)
- B. $\log[A]=\log[A]_0-kt/2.303$
- C. $1/[A]=1/[A]_0+kt$
- D. $k=2.303/t$
Explanation: Concentration falls linearly with time in zero-order reactions.
Integrated law
92. Integrated rate law for a second-order reaction in A is:
- A. $1/[A]=1/[A]_0+kt$ (Correct)
- B. $[A]=[A]_0-kt$
- C. $\log[A]=\log[A]_0-kt$
- D. $\Delta G=\Delta H-T\Delta S$
Explanation: This is the standard second-order integrated form.
Arrhenius
93. Arrhenius equation relates rate constant to:
- A. temperature and activation energy (Correct)
- B. pressure and volume
- C. mass and density
- D. pH and ionic strength
Explanation: It explains exponential temperature dependence.
Activation energy
94. Activation energy is the minimum energy needed for:
- A. effective collision (Correct)
- B. equilibrium
- C. phase change
- D. adsorption
Explanation: Only sufficiently energetic collisions can react.
Catalyst
95. A catalyst speeds up a reaction by:
- A. lowering activation energy (Correct)
- B. increasing enthalpy change
- C. changing equilibrium constant
- D. raising molecularity
Explanation: It offers an alternate lower-energy pathway.
Collision theory
96. According to collision theory, effective collisions require proper orientation and sufficient:
- A. energy (Correct)
- B. volume
- C. color
- D. mass
Explanation: Both conditions are needed for reaction.
Pseudo-first order
97. If one reactant is taken in large excess, a higher-order reaction may appear:
- A. pseudo-first order (Correct)
- B. zero order always
- C. third order always
- D. orderless
Explanation: The excess concentration stays nearly constant.
Radioactivity analogy
98. A process often following first-order kinetics is:
- A. radioactive decay (Correct)
- B. surface tension
- C. osmosis only
- D. simple melting
Explanation: Its rate is proportional to the amount remaining.
Graph
99. A straight line for zero-order kinetics is obtained by plotting:
- A. $[A]$ vs t (Correct)
- B. $\log[A]$ vs t
- C. $1/[A]$ vs t
- D. rate vs 1/[A]$
Explanation: Zero-order concentration falls linearly with time.
Graph
100. A straight line for first-order kinetics is obtained by plotting:
- A. $\log[A]$ vs t (Correct)
- B. $[A]$ vs t
- C. $1/[A]$ vs t
- D. k vs t
Explanation: The integrated first-order law is logarithmic.
Rate basics
101. Rate of reaction is the change in concentration of reactant or product per:
- A. unit time (Correct)
- B. unit pressure
- C. unit mass
- D. unit temperature
Explanation: Rate measures how fast concentration changes.
Average rate
102. Average rate over a time interval uses:
- A. change in concentration divided by time interval (Correct)
- B. final concentration only
- C. activation energy only
- D. equilibrium constant
Explanation: It is a finite-time rate measure.
Instantaneous rate
103. Instantaneous rate corresponds to the slope of concentration-time curve at a:
- A. particular instant (Correct)
- B. whole interval
- C. end point only
- D. midpoint only
Explanation: It is the tangent slope at that point.
Rate law
104. The rate law expresses rate as a function of:
- A. reactant concentrations raised to powers (Correct)
- B. product color only
- C. temperature alone
- D. equilibrium constant only
Explanation: Orders are determined experimentally.
Order
105. Overall order of reaction equals:
- A. sum of exponents in rate law (Correct)
- B. stoichiometric sum always
- C. difference of coefficients
- D. activation energy
Explanation: Order is obtained by adding the powers in the rate expression.
Molecularity
106. Molecularity refers to number of species colliding in an:
- A. elementary step (Correct)
- B. overall complex reaction
- C. equilibrium state
- D. catalyst surface
Explanation: Molecularity is defined only for elementary steps.
Order vs molecularity
107. Order of a reaction may be zero, fractional, or integral, while molecularity is:
- A. always a positive integer (Correct)
- B. always fractional
- C. always zero
- D. negative sometimes
Explanation: Molecularity counts discrete colliding species.
Zero order
108. For a zero-order reaction, rate is:
- A. independent of reactant concentration (Correct)
- B. directly proportional to concentration
- C. inversely proportional to concentration
- D. always zero
Explanation: The rate remains constant until reactant is exhausted enough.
First order
109. For a first-order reaction, rate is proportional to:
- A. first power of concentration (Correct)
- B. square of concentration
- C. cube of concentration
- D. pressure alone
Explanation: That is the defining rate law.
Second order
110. For a second-order reaction in one reactant A, rate is proportional to:
- A. $[A]^2$ (Correct)
- B. $[A]$
- C. $1/[A]$
- D. $[A]^0$
Explanation: Second-order dependence means square relation.
Units
111. Units of first-order rate constant are:
- A. s$^{-1}$ (Correct)
- B. mol L$^{-1}$ s$^{-1}$
- C. L mol$^{-1}$ s$^{-1}$
- D. mol$^{-2}$ L$^2$ s$^{-1}$
Explanation: First-order constant has dimension of inverse time.
Units
112. Units of second-order rate constant are:
- A. L mol$^{-1}$ s$^{-1}$ (Correct)
- B. s$^{-1}$
- C. mol L$^{-1}$ s$^{-1}$
- D. L$^2$ mol$^{-2}$ s$^{-1}$ only
Explanation: Second-order rate constant carries inverse concentration and time.
Half-life
113. For a first-order reaction, half-life is:
- A. independent of initial concentration (Correct)
- B. directly proportional to initial concentration
- C. inversely proportional to initial concentration
- D. zero
Explanation: This is a signature property of first-order kinetics.
Half-life
114. For a zero-order reaction, half-life is:
- A. directly proportional to initial concentration (Correct)
- B. independent of initial concentration
- C. inversely proportional to initial concentration
- D. infinite
Explanation: $t_{1/2}=[A]_0/2k$.
Integrated law
115. Integrated rate law for first-order reaction is:
- A. $k=\frac{2.303}{t}\log\frac{[A]_0}{[A]}$ (Correct)
- B. $[A]=[A]_0-kt$
- C. $1/[A]=1/[A]_0+kt$
- D. $\pi=CRT$
Explanation: This is the standard first-order integrated equation.
Integrated law
116. Integrated rate law for zero-order reaction is:
- A. $[A]=[A]_0-kt$ (Correct)
- B. $\log[A]=\log[A]_0-kt/2.303$
- C. $1/[A]=1/[A]_0+kt$
- D. $k=2.303/t$
Explanation: Concentration falls linearly with time in zero-order reactions.
Integrated law
117. Integrated rate law for a second-order reaction in A is:
- A. $1/[A]=1/[A]_0+kt$ (Correct)
- B. $[A]=[A]_0-kt$
- C. $\log[A]=\log[A]_0-kt$
- D. $\Delta G=\Delta H-T\Delta S$
Explanation: This is the standard second-order integrated form.
Arrhenius
118. Arrhenius equation relates rate constant to:
- A. temperature and activation energy (Correct)
- B. pressure and volume
- C. mass and density
- D. pH and ionic strength
Explanation: It explains exponential temperature dependence.
Activation energy
119. Activation energy is the minimum energy needed for:
- A. effective collision (Correct)
- B. equilibrium
- C. phase change
- D. adsorption
Explanation: Only sufficiently energetic collisions can react.
Catalyst
120. A catalyst speeds up a reaction by:
- A. lowering activation energy (Correct)
- B. increasing enthalpy change
- C. changing equilibrium constant
- D. raising molecularity
Explanation: It offers an alternate lower-energy pathway.
Collision theory
121. According to collision theory, effective collisions require proper orientation and sufficient:
- A. energy (Correct)
- B. volume
- C. color
- D. mass
Explanation: Both conditions are needed for reaction.
Pseudo-first order
122. If one reactant is taken in large excess, a higher-order reaction may appear:
- A. pseudo-first order (Correct)
- B. zero order always
- C. third order always
- D. orderless
Explanation: The excess concentration stays nearly constant.
Radioactivity analogy
123. A process often following first-order kinetics is:
- A. radioactive decay (Correct)
- B. surface tension
- C. osmosis only
- D. simple melting
Explanation: Its rate is proportional to the amount remaining.
Graph
124. A straight line for zero-order kinetics is obtained by plotting:
- A. $[A]$ vs t (Correct)
- B. $\log[A]$ vs t
- C. $1/[A]$ vs t
- D. rate vs 1/[A]$
Explanation: Zero-order concentration falls linearly with time.
Graph
125. A straight line for first-order kinetics is obtained by plotting:
- A. $\log[A]$ vs t (Correct)
- B. $[A]$ vs t
- C. $1/[A]$ vs t
- D. k vs t
Explanation: The integrated first-order law is logarithmic.

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