Q.1: For the reaction rate = k[A]2[B], the overall order is:
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Answer: (c)
Explanation:
Sum of powers = 2 + 1 = 3, so overall order is 3.
Q.2: Unit of the rate constant k for a first-order reaction is:
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Answer: (b)
Explanation:
First order has k with dimension of time−1.
Q.3: Half-life (t1/2) of a first-order reaction depends on:
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Answer: (b)
Explanation:
For first order, t1/2 = 0.693/k, independent of initial concentration.
Q.4: For a zero-order reaction, the plot of concentration [A] vs time (t) is:
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Answer: (a)
Explanation:
[A] = [A]0 − kt gives a straight line decreasing with t.
Q.5: The slope of ln [A] vs time for a first-order reaction equals:
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Answer: (b)
Explanation:
ln[A] = ln[A]0 − kt ⇒ slope = −k.
Q.6: In the Arrhenius equation k = A e−Ea/(RT), A represents:
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Answer: (b)
Explanation:
A is the pre-exponential/frequency factor related to collision frequency and orientation.
Q.7: If the rate doubles when temperature increases by 10 °C, the temperature coefficient (Q10) is:
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Answer: (c)
Explanation:
Q10 = Rate at (T+10)/Rate at T ≈ 2 for many reactions.
Q.8: The unit of k for a second-order reaction (with rate = k[A]2) is:
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Answer: (b)
Explanation:
For second order, k has unit (concentration)−1 time−1 = L mol−1 s−1.
Q.9: Pseudo-first order kinetics is observed when:
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Answer: (b)
Explanation:
Excess of one reactant makes its concentration effectively constant, reducing the rate law to first order.
Q.10: Molecularity of a reaction step is defined for:
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Answer: (b)
Explanation:
Molecularity refers to the number of species colliding in a single elementary step.
Q.11: For a first-order reaction, the time required to complete 75% of the reaction is:
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Answer: (b)
Explanation:
75% complete ⇒ 25% left = (1/4). For first order, time to reduce to 1/4 is 2 half-lives.
Q.12: In a plot of ln k vs 1/T, the slope equals:
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Answer: (b)
Explanation:
Arrhenius form ln k = ln A − (Ea/R)(1/T) ⇒ slope = −Ea/R.
Q.13: The average rate between t = 0 and t = 10 s is defined as:
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Answer: (b)
Explanation:
Average rate uses finite change: Δ[A]/Δt (with sign as per definition).
Q.14: A catalyst increases the reaction rate by:
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Answer: (b)
Explanation:
Catalysts provide an alternative pathway with lower activation energy; Keq is unchanged.
Q.15: For the reaction A → Products (first order), 80% completes in t seconds. The fraction remaining after time t is:
Show Answer ⯆
Answer: (b)
Explanation:
80% reacted ⇒ 20% left ⇒ fraction remaining = 0.2.
Q.1: The rate constant of a reaction depends on
(a) temperature
(b) pressure
(c) concentration
(d) volume
Q.2: For a first-order reaction, the half-life period is
(a) directly proportional to the initial concentration
(b) inversely proportional to the initial concentration
(c) independent of the initial concentration
(d) directly proportional to the square of the initial concentration
Q.3: The activation energy of a reaction can be determined by
(a) Vant Hoff equation
(b) Arrhenius equation
(c) Kirchhoff’s equation
(d) Gibbs-Helmholtz equation
Q.4: In a zero-order reaction, the rate of reaction is
(a) proportional to the concentration of reactants
(b) inversely proportional to the concentration of reactants
(c) independent of the concentration of reactants
(d) proportional to the square of the concentration of reactants
Q.5: The unit of rate constant for a second-order reaction is
(a) s⁻¹
(b) L mol⁻¹ s⁻¹
(c) mol L⁻¹ s⁻¹
(d) L² mol⁻² s⁻¹
Q.6: For a reaction with the following mechanism:
Step 1: A + B → C (slow)
Step 2: C + D → E (fast)
The rate-determining step is
(a) Step 1
(b) Step 2
(c) Both steps
(d) Neither step
Q.7: If the concentration of reactants is increased, the rate of reaction
(a) increases
(b) decreases
(c) remains the same
(d) may increase or decrease
Q.8: The Arrhenius equation is given by k = Ae^(-Ea/RT). In this equation, Ea stands for
(a) rate constant
(b) frequency factor
(c) activation energy
(d) gas constant
Q.9: The half-life of a reaction is 50 minutes at a certain initial concentration. If the reaction follows first-order kinetics, what will be the half-life if the initial concentration is doubled?
(a) 25 minutes
(b) 50 minutes
(c) 100 minutes
(d) 200 minutes
Q.10: For a reaction, the rate constant doubles when the temperature is increased from 300 K to 310 K. The activation energy of the reaction is approximately
(a) 48.3 kJ/mol
(b) 53.6 kJ/mol
(c) 41.5 kJ/mol
(d) 58.0 kJ/mol
Q.11: Which of the following statements is true for a zero-order reaction?
(a) The rate is proportional to the concentration of reactants.
(b) The rate is independent of the concentration of reactants.
(c) The rate decreases with time.
(d) The rate increases with time.
Q.12: The rate law for a reaction is given by rate = k[A]²[B]. If the concentration of A is doubled and the concentration of B is halved, the rate of the reaction will
(a) remain the same
(b) be halved
(c) be doubled
(d) be quadrupled
Q.13: The units of the rate constant for a first-order reaction are
(a) mol L⁻¹ s⁻¹
(b) L mol⁻¹ s⁻¹
(c) s⁻¹
(d) no units
Q.14: A reaction has a rate constant of 2.0 x 10⁻³ s⁻¹ at 25°C and an activation energy of 50 kJ/mol. What will be the rate constant at 35°C?
(a) 4.0 x 10⁻³ s⁻¹
(b) 2.4 x 10⁻³ s⁻¹
(c) 3.4 x 10⁻³ s⁻¹
(d) 1.0 x 10⁻³ s⁻¹
Q.15: The rate of a reaction is given by rate = k[A][B]². If the concentration of B is doubled, the rate of the reaction will increase by a factor of
(a) 2
(b) 4
(c) 8
(d) 16
Q.16: Which of the following statements is correct for a first-order reaction?
(a) The rate of reaction is proportional to the concentration of reactant.
(b) The rate of reaction is proportional to the square of the concentration of reactant.
(c) The rate of reaction is independent of the concentration of reactant.
(d) The rate of reaction is inversely proportional to the concentration of reactant.
Q.17: The half-life of a zero-order reaction is directly proportional to
(a) initial concentration of the reactant
(b) square of initial concentration of the reactant
(c) reciprocal of initial concentration of the reactant
(d) independent of initial concentration of the reactant
Q.18: For the reaction A → B, the rate law is rate = k[A]⁰. This implies
(a) the reaction is first-order with respect to A
(b) the reaction is second-order with respect to A
(c) the reaction is zero-order with respect to A
(d) the rate of the reaction is independent of the concentration of A
Q.19: The activation energy for a chemical reaction can be lowered by
(a) increasing the temperature
(b) increasing the concentration of reactants
(c) adding a catalyst
(d) changing the pressure
Q.20: For the reaction 2A + B → products, the following data were obtained:
[A] (M) [B] (M) Initial rate (M/s)
0.1 0.1 2.0 x 10⁻³
0.2 0.1 4.0 x 10⁻³
0.1 0.2 4.0 x 10⁻³
The rate law for the reaction is
(a) rate = k[A]²[B]
(b) rate = k[A][B]
(c) rate = k[A][B]²
(d) rate = k[A]²[B]²
Q.21: The pre-exponential factor (A) in the Arrhenius equation is
(a) related to the frequency of collisions
(b) the same for all reactions
(c) dependent on temperature
(d) dependent on the activation energy
Q.22: The rate of reaction is given by rate = k[A][B]. If the concentration of both A and B is doubled, the rate of the reaction will
(a) remain the same
(b) be doubled
(c) be quadrupled
(d) be halved
Q.23: For the reaction A + 2B → C, the following data were obtained:
[A] (M) [B] (M) Initial rate (M/s)
0.1 0.2 0.02
0.2 0.2 0.04
0.1 0.4 0.08
The rate law for the reaction is
(a) rate = k[A][B]²
(b) rate = k[A]²[B]
(c) rate = k[A][B]
(d) rate = k[A][B]³
Q.24: Which of the following is a characteristic of a zero-order reaction?
(a) The rate of reaction is proportional to the concentration of reactants.
(b) The rate of reaction is independent of the concentration of reactants.
(c) The rate of reaction decreases as the concentration of reactants decreases.
(d) The rate of reaction increases as the concentration of reactants increases.
Q.25: The rate constant for a first-order reaction is 0.693 min⁻¹. The time required to reduce the concentration of the reactant to half of its initial value is
(a) 1 min
(b) 10 min
(c) 0.693 min
(d) 2 min
Q.26: For the reaction 2A → B, the rate law is rate = k[A]². If the concentration of A is tripled, the rate of the reaction will
(a) remain the same
(b) be tripled
(c) be nine times
(d) be six times
Q.27: For the reaction A → B, the rate law is rate = k[A]². The unit of rate constant k is
(a) s⁻¹
(b) L mol⁻¹ s⁻¹
(c) L² mol⁻² s⁻¹
(d) mol L⁻¹ s⁻¹
Q.28: For a reaction, the rate constant (k) is 2.5 x 10⁻² s⁻¹. What is the order of the reaction?
(a) zero
(b) first
(c) second
(d) third
Q.29: Which of the following is the rate-determining step in a multi-step reaction?
(a) The fastest step
(b) The slowest step
(c) The step with the highest energy barrier
(d) The step with the lowest energy barrier
Q.30: For a first-order reaction, the plot of ln[A] vs. time is
(a) a straight line with a positive slope
(b) a straight line with a negative slope
(c) a curve
(d) a horizontal line
Q.31: The rate of a reaction increases with temperature because
(a) the activation energy increases
(b) the number of effective collisions increases
(c) the frequency factor decreases
(d) the rate constant decreases
Q.32: For a reaction, the rate law is given by rate = k[A][B]. What is the overall order of the reaction?
(a) zero
(b) first
(c) second
(d) third
Q.33: For a reaction A + B → C, the rate law is rate = k[A][B]. If the concentration of A is doubled and the concentration of B is kept constant, the rate of the reaction will
(a) remain the same
(b) be doubled
(c) be quadrupled
(d) be halved
Q.34: For the reaction 2A + B → C, the rate law is rate = k[A]²[B]. If the concentration of B is doubled, the rate of the reaction will
(a) remain the same
(b) be doubled
(c) be quadrupled
(d) be halved
Q.35: The rate constant of a reaction increases by a factor of 4 when the temperature is increased by 20°C. The activation energy of the reaction is
(a) 46.2 kJ/mol
(b) 58.0 kJ/mol
(c) 34.5 kJ/mol
(d) 41.5 kJ/mol
Q.36: The rate of a reaction is given by rate = k[A]²[B]. If the concentration of A is halved and the concentration of B is kept constant, the rate of the reaction will
(a) remain the same
(b) be halved
(c) be reduced to one-fourth
(d) be doubled
Q.37: The activation energy of a reaction is the energy required to
(a) break all the bonds in the reactants
(b) form the products
(c) form an activated complex
(d) form the reactants
Q.38: The rate of a reaction is given by rate = k[A][B]. If the concentration of both A and B is increased by a factor of 2, the rate of the reaction will
(a) remain the same
(b) be doubled
(c) be quadrupled
(d) be halved
Q.39: For a first-order reaction, the time taken for 99.9% completion is approximately
(a) 3.3 times the half-life
(b) 6.6 times the half-life
(c) 10 times the half-life
(d) 1.1 times the half-life
Q.40: The temperature coefficient of a reaction is defined as
(a) the ratio of rate constants at two different temperatures
(b) the ratio of activation energies at two different temperatures
(c) the ratio of the rate of reaction at two different temperatures
(d) the ratio of the rate of reaction to the activation energy
Q.41: For the reaction A + B → C, the rate law is rate = k[A]²[B]. If the concentration of A is doubled and the concentration of B is also doubled, the rate of the reaction will
(a) remain the same
(b) be doubled
(c) be quadrupled
(d) be increased eight times
Q.42: Which of the following factors does not affect the rate of a reaction?
(a) Temperature
(b) Pressure
(c) Catalyst
(d) Color of the reactants
Q.43: For a reaction, the rate law is given by rate = k[A]²[B]. If the concentration of A is tripled and the concentration of B is kept constant, the rate of the reaction will
(a) remain the same
(b) be tripled
(c) be nine times
(d) be six times
Q.44: The activation energy of a reaction is 50 kJ/mol and the rate constant at 300 K is 2 x 10⁻³ s⁻¹. What will be the rate constant at 320 K?
(a) 4 x 10⁻³ s⁻¹
(b) 6 x 10⁻³ s⁻¹
(c) 8 x 10⁻³ s⁻¹
(d) 10 x 10⁻³ s⁻¹
Q.45: For a reaction, the rate law is rate = k[A][B]. If the concentration of B is halved and the concentration of A is kept constant, the rate of the reaction will
(a) remain the same
(b) be halved
(c) be doubled
(d) be quadrupled
Q.46: The Arrhenius equation is given by k = Ae^(-Ea/RT). What does Ea represent in this equation?
(a) Activation energy
(b) Frequency factor
(c) Rate constant
(d) Temperature
Q.47: For a reaction 2A → B, the rate law is rate = k[A]². If the concentration of A is doubled, the rate of the reaction will
(a) remain the same
(b) be doubled
(c) be quadrupled
(d) be halved
Q.48: The unit of the rate constant for a first-order reaction is
(a) s⁻¹
(b) L mol⁻¹ s⁻¹
(c) L² mol⁻² s⁻¹
(d) mol L⁻¹ s⁻¹
Q.49: The rate constant for a second-order reaction is 0.2 L mol⁻¹ s⁻¹. What is the rate of reaction when the concentration of the reactant is 0.5 M?
(a) 0.05 M/s
(b) 0.1 M/s
(c) 0.2 M/s
(d) 0.4 M/s
Q.50: For a reaction, the rate law is given by rate = k[A]²[B]. If the concentration of A is doubled and the concentration of B is halved, the rate of the reaction will
(a) remain the same
(b) be doubled
(c) be halved
(d) be quadrupled
Q.51: The activation energy of a reaction is 60 kJ/mol. The rate constant at 300 K is 1.5 x 10⁻³ s⁻¹. What will be the rate constant at 320 K?
(a) 3.0 x 10⁻³ s⁻¹
(b) 6.0 x 10⁻³ s⁻¹
(c) 1.2 x 10⁻³ s⁻¹
(d) 2.0 x 10⁻³ s⁻¹
Q.52: The rate constant for a zero-order reaction is 0.1 mol L⁻¹ s⁻¹. What is the half-life of the reaction when the initial concentration of the reactant is 1 M?
(a) 5 s
(b) 10 s
(c) 15 s
(d) 20 s
Q.53: For a reaction, the rate law is rate = k[A][B]². What is the order of the reaction with respect to B?
(a) zero
(b) first
(c) second
(d) third
Q.54: For a reaction 2A → B, the rate law is rate = k[A]². If the concentration of A is increased by a factor of 4, the rate of the reaction will
(a) remain the same
(b) be doubled
(c) be quadrupled
(d) be increased sixteen times