Zero and first order kinetics half-lives Arrhenius equation and activation energy - Question Bank

1. The unit of the rate constant for a second-order reaction is:
A) s⁻¹
B) mol L⁻¹ s⁻¹
C) mol⁻¹ L s⁻¹
D) mol⁻² L² s⁻¹
2. According to the Arrhenius equation, what happens to the rate constant (k) when the temperature (T) increases?
A) k decreases
B) k increases
C) k remains constant
D) k becomes zero
3. The half-life of a zero-order reaction is 30 minutes when the initial concentration is 0.6 M. What would be the half-life if the initial concentration were 0.3 M?
A) 15 minutes
B) 30 minutes
C) 60 minutes
D) 90 minutes
4. For a second-order reaction where Rate = k[A]², if the initial concentration of A is doubled, how will the rate change?
A) Rate remains the same
B) Rate doubles
C) Rate triples
D) Rate increases by a factor of 4
5. Which statement about activation energy is incorrect?
A) It is the minimum energy for a reaction to occur.
B) It is always a positive value.
C) It is independent of temperature.
D) It can be lowered by a catalyst.
6. The slope of the plot of ln[A]t vs time for a first-order reaction is:
A) k
B) -k
C) 1/k
D) -1/k
7. If the initial concentration of a first-order reaction is [A]₀, what is the concentration after n half-lives?
A) [A]₀ / n
B) [A]₀ / 2n
C) [A]₀ / (2^n)
D) [A]₀ * (1/2)^n
8. A reaction proceeds with a constant rate of 0.1 M/s. What is the order of this reaction?
A) Zero-order
B) First-order
C) Second-order
D) Cannot be determined
9. The term 'frequency factor' (A) in the Arrhenius equation represents:
A) The number of collisions per unit volume per unit time
B) The fraction of collisions with energy greater than Ea
C) The rate constant at infinite temperature
D) The energy of activation
10. For a first-order reaction, the concentration of the reactant decreases from 0.8 M to 0.2 M in 10 minutes. What is the half-life of this reaction?
A) 5 minutes
B) 10 minutes
C) 20 minutes
D) 40 minutes
11. If the rate of a reaction is 1.5 x 10⁻³ M/s when the concentration of the reactant is 0.3 M, and the rate becomes 6.0 x 10⁻³ M/s when the concentration is 0.6 M, what is the order of the reaction?
A) Zero-order
B) First-order
C) Second-order
D) Third-order
12. The Arrhenius equation is given by k = A e^(-Ea/RT). If Ea = 0, then k will be equal to:
A) Zero
B) A
C) RT
D) A/RT
13. Which order of reaction has a half-life that is directly proportional to the initial concentration?
A) Zero-order
B) First-order
C) Second-order
D) Third-order
14. For a zero-order reaction, the rate of disappearance of reactant A is:
A) -d[A]/dt = k[A]
B) -d[A]/dt = k
C) -d[A]/dt = k[A]²
D) -d[A]/dt = k[A]⁰
15. According to the Arrhenius equation, at absolute zero temperature (T=0 K), the rate constant (k) approaches:
A) Infinity
B) Zero
C) A finite non-zero value
D) The pre-exponential factor A
16. The half-life of a first-order reaction is 20 minutes. How much time will it take for the concentration to reduce to 1/8th of its initial value?
A) 20 minutes
B) 40 minutes
C) 60 minutes
D) 80 minutes
17. If a reaction has a rate constant of 0.05 M⁻¹s⁻¹, what is the order of the reaction?
A) Zero-order
B) First-order
C) Second-order
D) Third-order
18. The integrated rate law for a first-order reaction can also be written as:
A) [A]t = [A]₀ - kt
B) log([A]t/[A]₀) = -kt/2.303
C) 1/[A]t = 1/[A]₀ + kt
D) [A]t = [A]₀ * kt
19. What is the effect of a catalyst on the activation energy of a reaction?
A) Increases activation energy
B) Decreases activation energy
C) Does not change activation energy
D) Makes activation energy zero
20. For a first-order reaction, if the initial concentration is 1.0 M and after 100 seconds it becomes 0.5 M, what is the half-life of this reaction?
A) 50 seconds
B) 100 seconds
C) 200 seconds
D) Cannot be determined without the rate constant
21. The rate of a zero-order reaction is given by Rate = k. This means:
A) The rate depends on the concentration of reactants.
B) The rate is constant regardless of reactant concentration.
C) The rate is inversely proportional to time.
D) The rate doubles with every 10°C increase in temperature.
22. In the Arrhenius equation, the term exp(-Ea/RT) represents the fraction of molecules that have:
A) Average kinetic energy
B) Energy equal to or greater than the activation energy
C) Zero kinetic energy
D) Less than the activation energy
23. For a zero-order reaction, what is the relationship between the half-life (t½) and the initial concentration ([A]₀)?
A) t½ is independent of [A]₀
B) t½ is directly proportional to [A]₀
C) t½ is inversely proportional to [A]₀
D) t½ is proportional to [A]₀²
24. If the half-life of a reaction is halved when the initial concentration is doubled, the reaction is:
A) Zero-order
B) First-order
C) Second-order
D) Third-order
25. The Arrhenius equation can be linearized by taking the logarithm of both sides. The equation becomes:
A) log k = log A - (Ea/2.303RT)
B) ln k = ln A - (Ea/RT)
C) k = A - (Ea/RT)
D) k = A * (Ea/RT)
26. What is the value of ln(2)?
A) 0.5
B) 1.0
C) 0.693
D) 1.44
27. The unit of the rate constant for a first-order reaction is:
A) M s⁻¹
B) s⁻¹
C) M⁻¹ s⁻¹
D) M⁻² s⁻¹
28. A reaction has a rate constant k = 5 x 10⁻⁴ M s⁻¹. What is the order of this reaction?
A) Zero-order
B) First-order
C) Second-order
D) Third-order
29. If the rate constant of a reaction doubles for every 10°C rise in temperature, this is a general rule of thumb related to:
A) Zero-order kinetics
B) First-order kinetics
C) Arrhenius equation behavior
D) Reaction order determination
30. For a first-order reaction, the half-life is constant and does not depend on the initial concentration. This is because:
A) The rate is proportional to the concentration.
B) The rate is independent of the concentration.
C) The rate is proportional to the square of the concentration.
D) The rate is proportional to the square root of the concentration.
31. What is the definition of activation energy?
A) The total energy of the reactants
B) The energy released during the reaction
C) The minimum energy required to initiate a chemical reaction
D) The energy of the products
32. The integrated rate law for a zero-order reaction A → Products is:
A) [A]t = [A]₀ - kt
B) ln[A]t = ln[A]₀ - kt
C) 1/[A]t = 1/[A]₀ + kt
D) [A]t = [A]₀ * e^(-kt)
33. For a zero-order reaction, the plot of concentration of reactant versus time is a:
A) Straight line with positive slope
B) Straight line with negative slope
C) Curve
D) Parabola
34. What happens to the rate constant 'k' of a reaction as the activation energy (Ea) increases, assuming temperature remains constant?
A) k increases
B) k decreases
C) k remains unchanged
D) k becomes zero
35. If a reaction has a half-life of 50 years, it is most likely:
A) A rapid reaction
B) A zero-order reaction with a high initial concentration
C) A first-order reaction
D) A second-order reaction with low concentration
36. The Arrhenius equation relates the rate constant (k) of a reaction to:
A) Temperature and activation energy
B) Concentration and time
C) Pressure and volume
D) Entropy and enthalpy
37. Which of the following statements is true for a zero-order reaction?
A) The rate of reaction depends on the concentration of the reactant.
B) The rate of reaction is constant and independent of reactant concentration.
C) The half-life is directly proportional to the initial concentration.
D) The integrated rate law is logarithmic.
38. For a first-order reaction, if the rate constant is 2 x 10⁻³ s⁻¹, what is its half-life in seconds?
A) 346.5
B) 173.25
C) 3.465
D) 693
39. What is the minimum energy required for reactant molecules to undergo a chemical reaction?
A) Kinetic energy
B) Potential energy
C) Activation energy
D) Thermal energy
40. The integrated rate law for a first-order reaction A → Products is given by:
A) [A]t = [A]₀ - kt
B) ln[A]t = ln[A]₀ - kt
C) 1/[A]t = 1/[A]₀ + kt
D) [A]t = [A]₀ * e^(-kt)
41. A reaction is found to have a rate constant that is independent of the initial concentration of the reactants. What is the order of this reaction?
A) First-order
B) Second-order
C) Zero-order
D) Third-order
42. What is the half-life of a zero-order reaction with an initial concentration [A]₀ and rate constant k?
A) t½ = [A]₀ / k
B) t½ = [A]₀ / (2k)
C) t½ = k / [A]₀
D) t½ = k / (2[A]₀)
43. If the temperature of a reaction is increased by 10°C, how does the rate constant typically change, according to empirical observations related to the Arrhenius equation?
A) It doubles
B) It triples
C) It increases by 5-10%
D) It remains unchanged
44. For a zero-order reaction, if the initial concentration of reactant A is 0.5 M and the rate constant is 0.02 M/s, what is the concentration of A after 10 seconds?
A) 0.1 M
B) 0.3 M
C) 0.5 M
D) 0.2 M
45. What is the unit of activation energy (Ea) in the Arrhenius equation?
A) J/mol
B) mol/J
C) s⁻¹
D) L/mol
46. In the Arrhenius equation, k = A exp(-Ea/RT), what does 'A' represent?
A) Activation energy
B) Gas constant
C) Frequency factor or pre-exponential factor
D) Temperature in Kelvin
47. The half-life of a first-order reaction is 10 minutes. What is the rate constant (k) in min⁻¹?
A) 0.693
B) 0.0693
C) 6.93
D) 1.44
48. For a first-order reaction, what is the relationship between the half-life (t½) and the initial concentration ([A]₀)?
A) t½ is directly proportional to [A]₀
B) t½ is inversely proportional to [A]₀
C) t½ is independent of [A]₀
D) t½ is proportional to [A]₀²
49. What is the unit of the rate constant for a zero-order reaction?
A) s⁻¹
B) mol L⁻¹ s⁻¹
C) mol⁻¹ L s⁻¹
D) mol⁻² L² s⁻¹
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