NEET UG - Half lives, Arrhenius theory, activation energy, collision theory for bimolecular gaseous reactions Online Test (MCQ Quiz)

1. What is the half-life of a first-order reaction?

A) Independent of the initial concentration B) Directly proportional to the initial concentration C) Inversely proportional to the initial concentration D) Proportional to the square of the initial concentration

2. For a zero-order reaction, the half-life is:

A) Independent of initial concentration B) Directly proportional to the initial concentration C) Inversely proportional to the initial concentration D) Zero

3. If the half-life of a reaction is 10 minutes, and it is a first-order reaction, how much time will it take for the concentration to reduce to 1/8th of its initial value?

A) 20 minutes B) 30 minutes C) 40 minutes D) 10 minutes

4. The Arrhenius equation relates the rate constant (k) of a reaction to:

A) Temperature and activation energy B) Concentration and activation energy C) Temperature and frequency factor D) Pressure and activation energy

5. In the Arrhenius equation, k = A * e^(-Ea/RT), what does 'A' represent?

A) Activation energy B) Gas constant C) Frequency factor or pre-exponential factor D) Rate constant

6. The term 'Ea' in the Arrhenius equation stands for:

A) Equilibrium constant B) Activation energy C) Enthalpy change D) Entropy change

7. According to the Arrhenius theory, what happens to the rate constant 'k' as temperature (T) increases?

A) Decreases B) Increases C) Remains constant D) Becomes zero

8. What is the minimum energy required for reactant molecules to undergo a chemical reaction called?

A) Kinetic energy B) Potential energy C) Activation energy D) Thermal energy

9. Which theory explains the rate of bimolecular reactions based on the frequency of collisions between reactant molecules?

A) Arrhenius theory B) Transition State theory C) Collision theory D) Thermodynamic theory

10. In collision theory, for a reaction to occur, the colliding molecules must possess:

A) Sufficient kinetic energy only B) Proper orientation only C) Both sufficient kinetic energy and proper orientation D) High potential energy

11. The fraction of collisions that have energy equal to or greater than the activation energy is represented by which term in the Arrhenius equation?

A) A B) e^(-Ea/RT) C) k D) R

12. For a second-order reaction, the half-life (t1/2) is related to the initial concentration ([A]0) as:

A) t1/2 ∝ [A]0 B) t1/2 ∝ 1/[A]0 C) t1/2 ∝ [A]0^2 D) t1/2 is independent of [A]0

13. What is the unit of the rate constant for a second-order reaction?

A) s^-1 B) L mol^-1 s^-1 C) mol L^-1 s^-1 D) mol^2 L^-2 s^-1

14. A catalyst increases the rate of a reaction by:

A) Increasing the activation energy B) Decreasing the activation energy C) Increasing the temperature D) Decreasing the concentration of reactants

15. Which of the following factors affects the rate of a chemical reaction according to collision theory?

A) Collision frequency B) Activation energy C) Orientation of colliding molecules D) All of the above

16. If the activation energy of a reaction is very high, the rate constant 'k' at a given temperature will be:

A) High B) Low C) Zero D) Infinite

17. The pre-exponential factor 'A' in the Arrhenius equation has the same units as:

A) The rate constant 'k' B) The activation energy 'Ea' C) The temperature 'T' D) The gas constant 'R'

18. For a bimolecular reaction, the rate law is generally expressed as:

A) Rate = k[A] B) Rate = k[A]^2 C) Rate = k[A][B] D) Rate = k

19. What does the term 'RT' in the exponent of the Arrhenius equation represent?

A) The activation energy B) The thermal energy available to molecules C) The frequency of collisions D) The probability of effective collisions

20. If the temperature is increased by 10°C, the rate of a reaction approximately doubles. This is a general observation for reactions with:

A) Low activation energy B) High activation energy C) Zero activation energy D) Negative activation energy

21. What is the half-life of a reaction if its rate is constant and does not depend on the concentration of reactants?

A) Decreases with time B) Increases with time C) Remains constant D) Becomes zero after some time

22. The collision theory is most applicable to which type of reactions?

A) Unimolecular reactions B) Bimolecular reactions C) Termolecular reactions D) Photochemical reactions

23. The probability that a collision between reactant molecules leads to a reaction is known as the:

A) Collision frequency B) Activation energy C) Steric factor or orientation factor D) Rate constant

24. If the activation energy (Ea) is zero, the rate constant 'k' according to Arrhenius equation becomes:

A) Zero B) A C) A * e D) A / e

25. The half-life of a second-order reaction A + B -> Products is given by t1/2 = 1 / (k[A]0) if [A]0 = [B]0. If the initial concentration is doubled, the new half-life will be:

A) Doubled B) Halved C) Four times D) One-fourth

26. Which of the following statements is true about activation energy?

A) It is the energy of the products. B) It is the energy of the reactants. C) It is the minimum energy required for a reaction to occur. D) It is the energy released during the reaction.

27. The Arrhenius equation can be written in logarithmic form as:

A) log k = log A - (Ea/RT) B) ln k = ln A - (Ea/RT) C) log k = log A + (Ea/RT) D) ln k = ln A + (Ea/RT)

28. In collision theory for bimolecular gaseous reactions, 'Zab' represents:

A) Activation energy B) Steric factor C) Collision frequency per unit volume D) Rate constant

29. If the initial concentration of a first-order reaction is halved, its half-life will:

A) Halve B) Double C) Remain the same D) Become zero

30. What is the effect of increasing temperature on the collision frequency of gas molecules?

A) Decreases B) Increases C) Remains constant D) Becomes zero

31. The rate of a reaction is independent of temperature if:

A) Ea is very high B) Ea is very low C) Ea is zero D) A is zero

32. For a reaction A + B -> Products, if the rate law is Rate = k[A][B], what is the order of the reaction?

A) Zero B) First C) Second D) Third

33. The 'effective collisions' in collision theory refer to collisions that have:

A) High kinetic energy B) Proper orientation C) Both sufficient energy and proper orientation D) Low activation energy

34. If the half-life of a reaction is 't', then after 2t, the remaining amount of reactant for a first-order reaction will be:

A) 1/2 of the initial amount B) 1/4 of the initial amount C) 1/8 of the initial amount D) 1/16 of the initial amount

35. The Arrhenius equation is given by k = A * e^(-Ea/RT). If we plot log k versus 1/T, we get a straight line with:

A) Slope = Ea/R and intercept = log A B) Slope = -Ea/R and intercept = log A C) Slope = Ea/2.303R and intercept = log A D) Slope = -Ea/2.303R and intercept = log A

36. According to collision theory, increasing the concentration of reactants leads to:

A) Increased activation energy B) Decreased activation energy C) Increased collision frequency D) Decreased collision frequency

37. For a zero-order reaction, the rate constant has the same units as:

A) Concentration B) Time C) Rate of reaction D) Half-life

38. The half-life of a reaction is the time required for the concentration of a reactant to reduce to:

A) 1/4 of its initial value B) 1/2 of its initial value C) 1/8 of its initial value D) 1/10 of its initial value

39. What is the relationship between the rate constant (k) and temperature (T) as described by Arrhenius equation?

A) k is inversely proportional to T B) k is directly proportional to T C) k increases exponentially with T D) k decreases exponentially with T

40. In the context of activation energy, the 'activated complex' or 'transition state' has:

A) Lower energy than reactants B) Higher energy than reactants C) Same energy as reactants D) Zero energy

41. For a second-order reaction where Rate = k[A]^2, if the initial concentration of A is doubled, the rate of reaction will increase by a factor of:

A) 2 B) 4 C) 8 D) 16

42. The collision theory states that the rate of a reaction is proportional to the frequency of collisions and the fraction of effective collisions. The fraction of effective collisions depends on:

A) Collision frequency and temperature B) Activation energy and orientation factor C) Concentration and pressure D) Volume and surface area

43. Which of the following is NOT a factor that influences the rate of a chemical reaction according to collision theory?

A) Concentration of reactants B) Temperature C) Nature of reactants D) Color of reactants

44. If a reaction has a half-life of 20 minutes and is first order, how long will it take for 75% of the reactant to be consumed?

A) 20 minutes B) 30 minutes C) 40 minutes D) 60 minutes

45. The activation energy of a reaction is 100 kJ/mol. At what temperature will the rate constant be approximately equal to the pre-exponential factor A?

A) 0 K B) 273 K C) Approx. 12000 K D) Approx. 1200 K

46. For a bimolecular reaction, the rate law is Rate = k[A][B]. If the concentration of both A and B are doubled, the rate of reaction will increase by a factor of:

A) 2 B) 3 C) 4 D) 8

47. The Arrhenius equation is most useful for determining the effect of which factor on the reaction rate?

A) Concentration B) Pressure C) Temperature D) Catalyst

48. In collision theory, the steric factor (p) accounts for:

A) The kinetic energy of molecules B) The potential energy of molecules C) The probability of effective orientation during collision D) The total number of collisions

49. The half-life of a reaction is 50 years. If it is a first-order reaction, what fraction of the substance will remain after 100 years?

A) 1/2 B) 1/4 C) 1/8 D) 1/16

Half lives, Arrhenius theory, activation energy, collision theory for bimolecular gaseous reactions - Online Test

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