MDCAT Chemical Equilibrium MCQs

This comprehensive set of MCQs on Chemical Equilibrium is designed to cover all essential topics required for success in the Medical and Dental College Admission Test (MDCAT). Focused on key concepts such as the dynamic nature of equilibrium, Le Chatelier’s principle, and equilibrium constants, these MCQs are crafted to help aspiring medical and dental students build a solid understanding of chemical equilibrium and its significance in chemistry and biological processes.

Who should practice Chemical Equilibrium MCQs?

Students preparing for the MDCAT who wish to strengthen their understanding of the principles of chemical equilibrium and its applications in real-life chemical reactions.
Individuals seeking to enhance their knowledge of equilibrium constants (Kc and Kp), reaction quotients, and factors that affect equilibrium, which are important for various medical and dental disciplines.
University students targeting high-yield topics like reversible reactions, the effect of concentration, pressure, and temperature on equilibrium, and industrial applications such as the Haber process.
Anyone aiming to build a deeper understanding of how equilibrium is maintained in biological systems, relevant to areas like respiratory physiology and metabolic pathways.
Candidates focused on developing critical thinking and analytical skills in applying Le Chatelier’s principle and interpreting equilibrium data.
Suitable for all students preparing for the MDCAT, including those looking to improve their problem-solving abilities and gain confidence in handling equilibrium-related questions in chemistry.

1. What is the rate of a chemical reaction?

A) The speed at which products are converted to reactants
B) The speed at which reactants are converted to products
C) The speed at which temperature changes
D) The speed at which pressure changes

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2. Which of the following can affect the rate of a reaction?

A) Temperature
B) Concentration
C) Surface area
D) All of the above

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3. What does the specific rate constant (k) depend on?

A) The temperature of the reaction
B) The concentration of reactants
C) The surface area of the reactants
D) The presence of a catalyst

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4. Which unit is used for the rate constant in a first-order reaction?

A) mol/L
B) s⁻¹
C) mol/L·s
D) L/mol·s

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5. What is the order of reaction if the rate of reaction doubles when the concentration of a reactant is doubled?

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

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6. How is the rate of a reaction measured?

A) By the change in concentration of reactants over time
B) By the change in temperature over time
C) By the change in pressure over time
D) By the change in color over time

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7. What happens to the rate of reaction when the concentration of reactants is increased?

A) It decreases
B) It increases
C) It remains the same
D) It fluctuates

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8. The unit of rate constant for a zero-order reaction is:

A) mol/L·s
B) L/mol·s
C) s⁻¹
D) mol/L

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9. In a second-order reaction, if the concentration of a reactant is doubled, the rate of the reaction will:

A) Remain the same
B) Double
C) Quadruple
D) Halve

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10. What is the definition of reaction rate?

A) The speed at which products are formed
B) The speed at which reactants are consumed
C) The change in concentration of reactants or products per unit time
D) All of the above

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11. The rate constant for a reaction is directly affected by:

A) Temperature
B) Pressure
C) Volume
D) Surface area

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12. If the rate of reaction does not change with the concentration of reactants, the order of reaction is:

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

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13. Which of the following factors increases the rate of a chemical reaction?

A) Increasing temperature
B) Decreasing surface area
C) Decreasing concentration
D) Removing a catalyst

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14. What is the rate law of a reaction?

A) A mathematical expression showing the relationship between the rate of reaction and concentration of reactants
B) A law stating the rate of reaction depends only on the products
C) A theory explaining how catalysts work
D) None of the above

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15. The unit of rate constant for a second-order reaction is:

A) mol/L·s
B) L/mol·s
C) s⁻¹
D) mol/L

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16. What does the slope of a concentration vs. time graph represent in a zero-order reaction?

A) The initial concentration
B) The rate constant (k)
C) The rate of reaction
D) The half-life

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17. Which factor has no effect on the rate of a chemical reaction?

A) Concentration
B) Surface area
C) Pressure
D) Color

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18. The rate of a reaction is directly proportional to the:

A) Concentration of products
B) Concentration of reactants
C) Pressure
D) Temperature

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19. A catalyst increases the rate of reaction by:

A) Raising the temperature of the system
B) Lowering the activation energy
C) Increasing the concentration of reactants
D) Changing the product formed

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20. The rate constant of a reaction is independent of:

A) Temperature
B) Concentration
C) Surface area
D) Activation energy

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21. The overall order of a reaction is the sum of:

A) The coefficients of the products
B) The exponents in the rate law expression
C) The concentration of all reactants
D) The units of the rate constant

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22. Which of the following is not a factor that affects the rate of reaction?

A) Catalyst
B) Surface area
C) Pressure
D) Molar mass

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23. The rate law for a second-order reaction with one reactant is:

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

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24. What is the unit of the rate constant for a reaction of zero order?

A) L/mol·s
B) mol/L·s
C) s⁻¹
D) L²/mol²·s

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25. In which type of reaction is the rate independent of reactant concentration?

A) Zero-order reaction
B) First-order reaction
C) Second-order reaction
D) Third-order reaction

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26. Which of the following statements is true for a first-order reaction?

A) The rate depends on the square of the reactant concentration.
B) The rate is independent of reactant concentration.
C) The rate depends on the concentration of one reactant.
D) The rate is directly proportional to the product concentration.

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27. Which of the following can change the rate constant (k) of a reaction?

A) Change in concentration
B) Change in temperature
C) Change in surface area
D) Change in pressure

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28. What happens to the rate constant when the temperature of the reaction increases?

A) It decreases
B) It increases
C) It remains constant
D) It fluctuates

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29. The reaction rate increases when the surface area of solid reactants is:

A) Increased
B) Decreased
C) Held constant
D) Ignored

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30. If a reaction is first order with respect to a reactant, then the rate law is:

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

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31. What is the rate-determining step in a reaction mechanism?

A) The fastest step
B) The slowest step
C) The first step
D) The step with the smallest activation energy

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32. What is the unit of the rate constant for a first-order reaction?

A) mol/L
B) L/mol·s
C) s⁻¹
D) mol/L·s

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33. What is the order of a reaction with a rate law: Rate = k[A][B]²?

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

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34. Which graph gives a straight line for a first-order reaction?

A) [A] vs. time
B) ln[A] vs. time
C) 1/[A] vs. time
D) t vs. 1/[A] View Answer

35. How does a catalyst affect a chemical reaction?

A) It increases the activation energy
B) It decreases the activation energy
C) It increases the concentration of reactants
D) It increases the equilibrium constant

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36. Which reaction order has a half-life independent of initial concentration?

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

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37. The rate constant of a second-order reaction is:

A) s⁻¹
B) L/mol·s
C) mol/L·s
D) L²/mol²·s

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38. If a reaction has a rate law: Rate = k[A][B], what is the order of the reaction with respect to A?

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

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39. What is the initial rate of a reaction?

A) The rate of reaction at the beginning
B) The rate of reaction at equilibrium
C) The rate of reaction when half the reactants are used
D) The rate of reaction when the products are formed

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40. The units of the rate constant for a third-order reaction are:

A) L/mol·s
B) L²/mol²·s
C) s⁻¹
D) mol/L·s

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41. Which factor is directly proportional to the rate of a reaction?

A) Temperature
B) Molar mass
C) Bond strength
D) Atomic size

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42. The rate of a chemical reaction increases with an increase in temperature because:

A) More collisions have the required activation energy
B) The activation energy increases
C) The volume of reactants increases
D) The concentration of reactants increases

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43. In a zero-order reaction, the rate is:

A) Independent of the concentration of reactants
B) Directly proportional to the concentration of reactants
C) Inversely proportional to the concentration of reactants
D) Dependent on the product concentration

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44. Which of the following is a second-order reaction?

A) Rate = k[A] B) Rate = k[A]²
C) Rate = k[A][B] D) Both B and C

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45. If the rate of a reaction depends on the concentration of only one reactant, the reaction is classified as:

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

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46. How does increasing the concentration of reactants affect the rate of a reaction?

A) It decreases the rate
B) It increases the rate
C) It has no effect
D) It stops the reaction

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47. The rate of reaction depends on:

A) The concentration of reactants
B) The concentration of products
C) The temperature of the system
D) Both A and C

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48. What is the half-life of a reaction?

A) The time it takes for the reaction to finish
B) The time it takes for half the reactants to be used up
C) The time it takes for the products to be formed
D) The time it takes for the rate to decrease by half

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49. For a reaction with a rate law: Rate = k[A]², the reaction is:

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

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50. If a reaction has a rate law: Rate = k[A]⁰, the rate is:

A) Proportional to the concentration of A
B) Independent of the concentration of A
C) Inversely proportional to the concentration of A
D) None of the above

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51. Which factor does not affect the rate of a chemical reaction?

A) Temperature
B) Catalyst
C) Particle size
D) Volume of the container

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52. The unit of the rate constant for a first-order reaction is:

A) mol/L·s
B) L/mol·s
C) s⁻¹
D) mol²/L²·s

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53. In a second-order reaction, the rate depends on:

A) The square of the concentration of one reactant
B) The sum of the concentrations of reactants
C) The product of the concentrations of two reactants
D) Either A or C

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54. The rate of reaction is defined as:

A) The speed at which products are formed
B) The speed at which reactants are consumed
C) The change in concentration of reactants or products per unit time
D) All of the above

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55. Which of the following does not appear in the rate law expression?

A) Reactant concentration
B) Product concentration
C) Rate constant
D) Temperature

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56. The half-life of a zero-order reaction is:

A) Proportional to the initial concentration
B) Independent of the initial concentration
C) Inversely proportional to the initial concentration
D) Proportional to the rate constant

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57. In a second-order reaction, doubling the concentration of a reactant will:

A) Double the rate
B) Quadruple the rate
C) Halve the rate
D) Not affect the rate

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58. The unit of rate constant for a third-order reaction is:

A) mol/L·s
B) L²/mol²·s
C) s⁻¹
D) mol/L

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59. What is the effect of a catalyst on the activation energy of a reaction?

A) It increases the activation energy
B) It decreases the activation energy
C) It has no effect on the activation energy
D) It increases the energy of the reactants

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60. If the rate law is Rate = k[A]³, the reaction is:

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

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61. What is the effect of increasing temperature on the rate of a reaction?

A) It decreases the rate
B) It increases the rate
C) It has no effect on the rate
D) It decreases the activation energy

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62. In a reaction where the rate law is Rate = k[A][B], what will happen if the concentration of A is doubled?

A) The rate will double
B) The rate will halve
C) The rate will quadruple
D) The rate will not change

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63. The unit of the rate constant for a zero-order reaction is:

A) mol/L·s
B) L/mol·s
C) s⁻¹
D) L²/mol²·s

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64. The rate of a reaction is influenced by all of the following factors except:

A) Surface area of the reactants
B) Presence of a catalyst
C) Color of the reactants
D) Temperature

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65. For a reaction: A + B → C, if the rate law is Rate = k[A][B], what happens if the concentration of both A and B are doubled?

A) The rate doubles
B) The rate remains unchanged
C) The rate quadruples
D) The rate halves

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66. Which factor increases the rate of reaction by lowering the activation energy?

A) Increasing the concentration of reactants
B) Adding a catalyst
C) Decreasing the temperature
D) Increasing the pressure

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67. What is the order of a reaction with the rate law: Rate = k[A][B]²?

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

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68. Which factor is least likely to affect the rate of a chemical reaction?

A) Concentration of reactants
B) Surface area of reactants
C) Nature of reactants
D) Color of reactants

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69. If the concentration of a reactant is halved in a first-order reaction, the rate will:

A) Halve
B) Double
C) Stay the same
D) Quadruple

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70. The rate of a chemical reaction is inversely proportional to:

A) Temperature
B) Concentration of reactants
C) Activation energy
D) Pressure

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71. What is the role of a catalyst in a chemical reaction?

A) It increases the activation energy
B) It decreases the activation energy
C) It alters the concentration of reactants
D) It decreases the temperature of the reaction

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72. In a first-order reaction, the half-life is:

A) Proportional to the concentration
B) Independent of the concentration
C) Inversely proportional to the concentration
D) Dependent on the temperature

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73. What happens to the rate of a reaction when a catalyst is added?

A) It increases
B) It decreases
C) It remains the same
D) It becomes zero

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74. The rate constant (k) for a second-order reaction has units of:

A) mol/L·s
B) L/mol·s
C) s⁻¹
D) mol/L

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75. If the rate of a reaction is independent of the concentration of the reactants, the reaction is:

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

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76. In a reaction, if doubling the concentration of one reactant causes the rate to quadruple, the order of the reaction with respect to that reactant is:

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

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77. The rate law for a reaction is determined by:

A) The balanced chemical equation
B) Experimental data
C) The molecular weight of the reactants
D) The phase of the reactants

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78. Which of the following factors will not affect the rate of a reaction?

A) The presence of a catalyst
B) The concentration of reactants
C) The phase of the products
D) The temperature of the reaction

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79. The rate of a reaction generally increases with an increase in temperature because:

A) The activation energy decreases
B) The frequency of collisions increases
C) The concentration of products increases
D) The reaction becomes more exothermic

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80. Which of the following statements about catalysts is false?

A) Catalysts increase the rate of reaction
B) Catalysts decrease the activation energy
C) Catalysts change the equilibrium constant
D) Catalysts provide an alternative reaction pathway

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81. If a reaction has a rate law: Rate = k[A]²[B], the reaction is:

A) First-order
B) Second-order
C) Third-order
D) Fourth-order

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82. What effect does increasing the surface area of a solid reactant have on the reaction rate?

A) It decreases the rate
B) It increases the rate
C) It has no effect on the rate
D) It decreases the activation energy

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83. For a second-order reaction, the half-life is:

A) Proportional to the initial concentration
B) Independent of the initial concentration
C) Inversely proportional to the initial concentration
D) Dependent on the volume of the reaction

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84. In a first-order reaction, the rate is:

A) Proportional to the concentration of one reactant
B) Proportional to the square of the concentration of one reactant
C) Independent of the concentration of reactants
D) Proportional to the product of the concentration of two reactants

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85. The unit of the rate constant for a first-order reaction is:

A) mol/L
B) L/mol·s
C) s⁻¹
D) mol/L·s

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86. Which graph gives a straight line for a second-order reaction?

A) [A] vs. time
B) ln[A] vs. time
C) 1/[A] vs. time
D) ln(k) vs. 1/T

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87. What is the rate constant for a zero-order reaction with a rate of 0.2 mol/L·s and an initial concentration of 0.4 mol/L?

A) 0.2 mol/L·s
B) 0.4 mol/L·s
C) 0.1 mol/L·s
D) 0.5 mol/L·s

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88. In which type of reaction is the rate constant independent of the reactant concentration?

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

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89. For a second-order reaction, doubling the concentration of a reactant will:

A) Double the rate
B) Quadruple the rate
C) Halve the rate
D) Not affect the rate

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90. The rate law for a reaction is given as: Rate = k[A]²[B]. What happens if the concentration of B is doubled?

A) The rate will quadruple
B) The rate will double
C) The rate will remain the same
D) The rate will halve

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91. Which of the following is a property of a first-order reaction?

A) The half-life is independent of the initial concentration
B) The rate is proportional to the square of the concentration of the reactant
C) The rate is independent of the concentration of reactants
D) The rate is proportional to the concentration of two reactants

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92. What is the unit of the rate constant for a third-order reaction?

A) mol/L·s
B) L/mol·s
C) L²/mol²·s
D) s⁻¹

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93. The rate of a chemical reaction can be increased by:

A) Lowering the concentration of reactants
B) Decreasing the temperature
C) Increasing the surface area of reactants
D) Decreasing the pressure

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94. For a zero-order reaction, the rate is:

A) Proportional to the concentration of one reactant
B) Proportional to the square of the concentration of one reactant
C) Independent of the concentration of reactants
D) Dependent on the product concentration

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95. Which of the following is true for a first-order reaction?

A) The half-life decreases with decreasing concentration
B) The half-life increases with increasing concentration
C) The half-life remains constant
D) The half-life depends on the rate constant

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96. In which order of reaction does the rate of reaction depend on the concentration of more than one reactant?

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

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97. The Arrhenius equation relates the rate constant to:

A) Temperature and activation energy
B) Pressure and volume
C) Concentration and temperature
D) Surface area and volume

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98. The rate constant for a reaction can be determined using:

A) The temperature of the reaction
B) The initial concentration of reactants
C) The order of the reaction
D) Experimental data

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99. For a second-order reaction, the plot of 1/[A] vs. time gives:

A) A straight line
B) A parabola
C) An exponential curve
D) A logarithmic curve

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100. What is the effect of increasing the temperature on the rate constant of a reaction?

A) It increases
B) It decreases
C) It remains constant
D) It becomes zero

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