Chemical Kinetics MCQ Quiz - Objective Question with Answer for Chemical Kinetics - Download Free PDF

Last updated on Jun 24, 2025

Latest Chemical Kinetics MCQ Objective Questions

Chemical Kinetics Question 1:

The reaction rate constant can be defined as the rate of reaction when each reactant's concentration is

  1. Infinite
  2. Doubled the initial concentration
  3. Zero
  4. Unity

Answer (Detailed Solution Below)

Option 4 : Unity

Chemical Kinetics Question 1 Detailed Solution

The correct answer is Unity.

Key Points

  • The reaction rate constant (k) is defined as the rate of reaction when the concentration of each reactant is kept at unity (1 mol/L).
  • It provides a measure of the intrinsic speed of a chemical reaction, independent of reactant concentrations.
  • The rate constant is specific to a particular reaction and depends on temperature and the presence of a catalyst.
  • It is denoted by "k" in rate equations and varies for different orders of reactions (e.g., zero-order, first-order, second-order).
  • The units of the rate constant depend on the reaction order; for example, s-1 for first-order reactions and L·mol-1·s-1 for second-order reactions.

Additional Information

  • Rate Equation: The rate of a chemical reaction is represented as Rate = k [A]m[B]n, where m and n are reaction orders for reactants A and B.
  • Arrhenius Equation: The rate constant k is temperature-dependent and can be expressed as k = A·e-Ea/RT, where A is the pre-exponential factor, Ea is the activation energy, R is the gas constant, and T is the absolute temperature.
  • Reaction Order: The sum of the powers of the concentration terms in the rate equation determines the reaction order (e.g., first-order, second-order).
  • Units of Rate Constant: For zero-order reactions, k has units of mol·L-1·s-1; for first-order reactions, s-1; and for second-order reactions, L·mol-1·s-1.
  • Factors Influencing Rate Constant: Temperature, the presence of a catalyst, and the nature of the reactants affect the magnitude of the rate constant.

Chemical Kinetics Question 2:

The type of reaction that is typically found when a material that is required for the reaction to proceed, such as a surface or a catalyst, is saturated by the reactants is called a ________ order reaction.

  1. first
  2. second
  3. zero
  4. third

Answer (Detailed Solution Below)

Option 3 : zero

Chemical Kinetics Question 2 Detailed Solution

The correct answer is zero order reaction.

Key Points

  • In a zero-order reaction, the rate of reaction is independent of the concentration of the reactants.
  • These reactions are commonly seen in catalytic processes where the catalyst surface is saturated by the reactants.
  • In such reactions, the rate of reaction remains constant until the reactant concentration is significantly depleted.
  • Zero-order kinetics is often observed in heterogeneous catalysis and other situations where a limiting step is saturated.

Additional Information

  • First-order Reaction
    • A first-order reaction is one where the rate is directly proportional to the concentration of one reactant.
    • The rate law for a first-order reaction can be expressed as: Rate = k[A], where k is the rate constant and [A] is the concentration of the reactant.
    • These reactions often involve unimolecular processes.
    • Examples include radioactive decay and certain substitution reactions in organic chemistry.
  • Second-order Reaction
    • A second-order reaction's rate is proportional to the square of the concentration of one reactant or the product of the concentrations of two reactants.
    • The rate law can be written as: Rate = k[A]^2 or Rate = k[A][B], depending on the reaction mechanism.
    • These reactions often involve bimolecular processes.
    • Examples include the reaction between hydrogen and iodine to form hydrogen iodide.
  • Third-order Reaction
    • A third-order reaction's rate depends on the concentration of three reactants or the concentration of one reactant raised to the third power, or other combinations summing to three.
    • The rate law can be expressed as: Rate = k[A]^3 or other combinations.
    • These reactions are less common compared to first and second-order reactions.
    • An example is the reaction between nitric oxide and oxygen to form nitrogen dioxide.

Chemical Kinetics Question 3:

For a chemical reaction with rise in temperature by 10°, the rate constant becomes nearly ________________.

  1. Double
  2. Triple
  3. one-fourth
  4. half

Answer (Detailed Solution Below)

Option 1 : Double

Chemical Kinetics Question 3 Detailed Solution

The correct answer is Double.

Key Points

  • For many chemical reactions, the rate constant approximately doubles with a 10°C increase in temperature.
  • This phenomenon is often referred to as the "rule of thumb" in chemical kinetics.
  • The temperature dependence of the rate constant is described by the Arrhenius equation.
  • According to the Arrhenius equation, the rate constant (k) is related to temperature (T) through the exponential factor involving activation energy (Ea) and the gas constant (R).

Additional Information

  • Arrhenius Equation:
    • The Arrhenius equation is k = A * exp(-Ea/(RT)), where k is the rate constant, A is the pre-exponential factor (frequency of collisions), Ea is the activation energy, R is the gas constant, and T is the temperature in Kelvin.
    • This equation shows the relationship between the rate constant and temperature, indicating that as temperature increases, the rate constant increases exponentially.
  • Activation Energy (Ea):
    • Activation energy is the minimum energy that reacting molecules must possess to undergo a chemical reaction.
    • Higher activation energy means that fewer molecules have sufficient energy to react at a given temperature.
  • Gas Constant (R):
    • The gas constant (R) is a physical constant that appears in many fundamental equations in physical sciences, such as the ideal gas law and the Arrhenius equation.
    • The value of R is 8.314 J/(mol·K).
  • Rule of Thumb in Chemical Kinetics:
    • The "rule of thumb" in chemical kinetics suggests that for many reactions, the rate constant approximately doubles for every 10°C rise in temperature.
    • This empirical rule helps chemists estimate the effect of temperature changes on reaction rates without detailed calculations.

Chemical Kinetics Question 4:

The decomposition of gaseous Ammonia on a hot platinum surface is a _______________ order reaction at high pressure.

  1. two
  2. zero
  3. three
  4. one

Answer (Detailed Solution Below)

Option 2 : zero

Chemical Kinetics Question 4 Detailed Solution

The correct answer is zero.

Key Points

  • Ammonia (NH3):
    • Ammonia is produced in large quantities worldwide for use as a fertilizer and as a primary source of nitrogen in the production of many chemicals. Liquid ammonia can be sprayed directly into the soil as a fertilizer, or it can be converted to ammonium salts (nitrate, sulfate or phosphate) for solid fertilizers.
  • It is a colourless gas with a pungent smell and can be toxic when exposed to higher concentration levels. It is highly soluble in water and basic in nature
  • Nitrogen (Z=7), its ground state electronic configuration is \(1s^2 2s^2 2p^3 \) and the observed valency is 3. At the time of hybridization, one 2s and three 2p orbitals mix to form four sp3 hybridized orbitals. Out of the four hybrid orbitals, one contains a lone pair of electrons and the other three are half filled.

qImage6790f972d96db8e332b24d05

  • Three half-filled sp3 hybrid orbitals of N atom overlap with half-filled 1s orbital of three hydrogen atoms to form three sigma covalent bonds. Thus, in NH3 molecule, there are three bonding pairs of electrons and one lone pair of electrons.

drawing1 56c84c3dd4620

  • This single lone pair distorts the bond angle of H-N-H to107.5°. and therefore due to the lone pair effect, the structure of the NH3 molecule is pyramidal with nitrogen at the tip.

Structureofammonia

Top Chemical Kinetics MCQ Objective Questions

The reaction rate constant can be defined as the rate of reaction when each reactant's concentration is

  1. Infinite
  2. Doubled the initial concentration
  3. Zero
  4. Unity

Answer (Detailed Solution Below)

Option 4 : Unity

Chemical Kinetics Question 5 Detailed Solution

Download Solution PDF

The correct answer is Unity.

Key Points

  • The reaction rate constant (k) is defined as the rate of reaction when the concentration of each reactant is kept at unity (1 mol/L).
  • It provides a measure of the intrinsic speed of a chemical reaction, independent of reactant concentrations.
  • The rate constant is specific to a particular reaction and depends on temperature and the presence of a catalyst.
  • It is denoted by "k" in rate equations and varies for different orders of reactions (e.g., zero-order, first-order, second-order).
  • The units of the rate constant depend on the reaction order; for example, s-1 for first-order reactions and L·mol-1·s-1 for second-order reactions.

Additional Information

  • Rate Equation: The rate of a chemical reaction is represented as Rate = k [A]m[B]n, where m and n are reaction orders for reactants A and B.
  • Arrhenius Equation: The rate constant k is temperature-dependent and can be expressed as k = A·e-Ea/RT, where A is the pre-exponential factor, Ea is the activation energy, R is the gas constant, and T is the absolute temperature.
  • Reaction Order: The sum of the powers of the concentration terms in the rate equation determines the reaction order (e.g., first-order, second-order).
  • Units of Rate Constant: For zero-order reactions, k has units of mol·L-1·s-1; for first-order reactions, s-1; and for second-order reactions, L·mol-1·s-1.
  • Factors Influencing Rate Constant: Temperature, the presence of a catalyst, and the nature of the reactants affect the magnitude of the rate constant.

Chemical Kinetics Question 6:

The decomposition of gaseous Ammonia on a hot platinum surface is a _______________ order reaction at high pressure.

  1. two
  2. zero
  3. three
  4. one

Answer (Detailed Solution Below)

Option 2 : zero

Chemical Kinetics Question 6 Detailed Solution

The correct answer is zero.

Key Points

  • Ammonia (NH3):
    • Ammonia is produced in large quantities worldwide for use as a fertilizer and as a primary source of nitrogen in the production of many chemicals. Liquid ammonia can be sprayed directly into the soil as a fertilizer, or it can be converted to ammonium salts (nitrate, sulfate or phosphate) for solid fertilizers.
  • It is a colourless gas with a pungent smell and can be toxic when exposed to higher concentration levels. It is highly soluble in water and basic in nature
  • Nitrogen (Z=7), its ground state electronic configuration is \(1s^2 2s^2 2p^3 \) and the observed valency is 3. At the time of hybridization, one 2s and three 2p orbitals mix to form four sp3 hybridized orbitals. Out of the four hybrid orbitals, one contains a lone pair of electrons and the other three are half filled.

qImage6790f972d96db8e332b24d05

  • Three half-filled sp3 hybrid orbitals of N atom overlap with half-filled 1s orbital of three hydrogen atoms to form three sigma covalent bonds. Thus, in NH3 molecule, there are three bonding pairs of electrons and one lone pair of electrons.

drawing1 56c84c3dd4620

  • This single lone pair distorts the bond angle of H-N-H to107.5°. and therefore due to the lone pair effect, the structure of the NH3 molecule is pyramidal with nitrogen at the tip.

Structureofammonia

Chemical Kinetics Question 7:

For a chemical reaction with rise in temperature by 10°, the rate constant becomes nearly ________________.

  1. Double
  2. Triple
  3. one-fourth
  4. half

Answer (Detailed Solution Below)

Option 1 : Double

Chemical Kinetics Question 7 Detailed Solution

The correct answer is Double.

Key Points

  • For many chemical reactions, the rate constant approximately doubles with a 10°C increase in temperature.
  • This phenomenon is often referred to as the "rule of thumb" in chemical kinetics.
  • The temperature dependence of the rate constant is described by the Arrhenius equation.
  • According to the Arrhenius equation, the rate constant (k) is related to temperature (T) through the exponential factor involving activation energy (Ea) and the gas constant (R).

Additional Information

  • Arrhenius Equation:
    • The Arrhenius equation is k = A * exp(-Ea/(RT)), where k is the rate constant, A is the pre-exponential factor (frequency of collisions), Ea is the activation energy, R is the gas constant, and T is the temperature in Kelvin.
    • This equation shows the relationship between the rate constant and temperature, indicating that as temperature increases, the rate constant increases exponentially.
  • Activation Energy (Ea):
    • Activation energy is the minimum energy that reacting molecules must possess to undergo a chemical reaction.
    • Higher activation energy means that fewer molecules have sufficient energy to react at a given temperature.
  • Gas Constant (R):
    • The gas constant (R) is a physical constant that appears in many fundamental equations in physical sciences, such as the ideal gas law and the Arrhenius equation.
    • The value of R is 8.314 J/(mol·K).
  • Rule of Thumb in Chemical Kinetics:
    • The "rule of thumb" in chemical kinetics suggests that for many reactions, the rate constant approximately doubles for every 10°C rise in temperature.
    • This empirical rule helps chemists estimate the effect of temperature changes on reaction rates without detailed calculations.

Chemical Kinetics Question 8:

The type of reaction that is typically found when a material that is required for the reaction to proceed, such as a surface or a catalyst, is saturated by the reactants is called a ________ order reaction.

  1. first
  2. second
  3. zero
  4. third

Answer (Detailed Solution Below)

Option 3 : zero

Chemical Kinetics Question 8 Detailed Solution

The correct answer is zero order reaction.

Key Points

  • In a zero-order reaction, the rate of reaction is independent of the concentration of the reactants.
  • These reactions are commonly seen in catalytic processes where the catalyst surface is saturated by the reactants.
  • In such reactions, the rate of reaction remains constant until the reactant concentration is significantly depleted.
  • Zero-order kinetics is often observed in heterogeneous catalysis and other situations where a limiting step is saturated.

Additional Information

  • First-order Reaction
    • A first-order reaction is one where the rate is directly proportional to the concentration of one reactant.
    • The rate law for a first-order reaction can be expressed as: Rate = k[A], where k is the rate constant and [A] is the concentration of the reactant.
    • These reactions often involve unimolecular processes.
    • Examples include radioactive decay and certain substitution reactions in organic chemistry.
  • Second-order Reaction
    • A second-order reaction's rate is proportional to the square of the concentration of one reactant or the product of the concentrations of two reactants.
    • The rate law can be written as: Rate = k[A]^2 or Rate = k[A][B], depending on the reaction mechanism.
    • These reactions often involve bimolecular processes.
    • Examples include the reaction between hydrogen and iodine to form hydrogen iodide.
  • Third-order Reaction
    • A third-order reaction's rate depends on the concentration of three reactants or the concentration of one reactant raised to the third power, or other combinations summing to three.
    • The rate law can be expressed as: Rate = k[A]^3 or other combinations.
    • These reactions are less common compared to first and second-order reactions.
    • An example is the reaction between nitric oxide and oxygen to form nitrogen dioxide.

Chemical Kinetics Question 9:

The reaction rate constant can be defined as the rate of reaction when each reactant's concentration is

  1. Infinite
  2. Doubled the initial concentration
  3. Zero
  4. Unity

Answer (Detailed Solution Below)

Option 4 : Unity

Chemical Kinetics Question 9 Detailed Solution

The correct answer is Unity.

Key Points

  • The reaction rate constant (k) is defined as the rate of reaction when the concentration of each reactant is kept at unity (1 mol/L).
  • It provides a measure of the intrinsic speed of a chemical reaction, independent of reactant concentrations.
  • The rate constant is specific to a particular reaction and depends on temperature and the presence of a catalyst.
  • It is denoted by "k" in rate equations and varies for different orders of reactions (e.g., zero-order, first-order, second-order).
  • The units of the rate constant depend on the reaction order; for example, s-1 for first-order reactions and L·mol-1·s-1 for second-order reactions.

Additional Information

  • Rate Equation: The rate of a chemical reaction is represented as Rate = k [A]m[B]n, where m and n are reaction orders for reactants A and B.
  • Arrhenius Equation: The rate constant k is temperature-dependent and can be expressed as k = A·e-Ea/RT, where A is the pre-exponential factor, Ea is the activation energy, R is the gas constant, and T is the absolute temperature.
  • Reaction Order: The sum of the powers of the concentration terms in the rate equation determines the reaction order (e.g., first-order, second-order).
  • Units of Rate Constant: For zero-order reactions, k has units of mol·L-1·s-1; for first-order reactions, s-1; and for second-order reactions, L·mol-1·s-1.
  • Factors Influencing Rate Constant: Temperature, the presence of a catalyst, and the nature of the reactants affect the magnitude of the rate constant.
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