Q.1 The rate of a reaction depends on:
Concentration of reactants
Temperature
Presence of catalyst
All of the above
Explanation - The rate of reaction is influenced by reactant concentrations, temperature, and catalysts which can speed up the reaction.
Correct answer is: All of the above
Q.2 The order of reaction with respect to a reactant is determined by:
Stoichiometry of the reaction
Rate law experiments
Molecular weight of reactants
Equilibrium constant
Explanation - The reaction order is experimentally determined from the rate law, not directly from stoichiometry.
Correct answer is: Rate law experiments
Q.3 For a first-order reaction, the half-life is:
Dependent on initial concentration
Independent of initial concentration
Zero
Dependent on temperature only
Explanation - For first-order reactions, half-life t1/2 = 0.693/k, which does not depend on initial concentration.
Correct answer is: Independent of initial concentration
Q.4 A reaction that occurs in a single step is called:
Complex reaction
Elementary reaction
Chain reaction
Photochemical reaction
Explanation - An elementary reaction occurs in a single step with a single transition state.
Correct answer is: Elementary reaction
Q.5 The rate constant of a reaction increases with:
Increase in temperature
Decrease in concentration
Decrease in pressure
Decrease in temperature
Explanation - According to the Arrhenius equation, rate constant k increases exponentially with temperature.
Correct answer is: Increase in temperature
Q.6 The unit of rate constant for a second-order reaction (A → products) is:
s⁻¹
M⁻¹s⁻¹
M s⁻¹
s² M⁻¹
Explanation - For second-order reactions, rate = k[A]², giving k units as M⁻¹s⁻¹.
Correct answer is: M⁻¹s⁻¹
Q.7 The reaction A → products has a rate law: rate = k[A][B]. Its order is:
1
2
3
0
Explanation - Overall reaction order is sum of exponents: 1 + 1 = 2.
Correct answer is: 2
Q.8 Activation energy of a reaction is:
Energy released in reaction
Minimum energy required for reaction
Difference in bond energies
None of the above
Explanation - Activation energy is the minimum energy molecules must possess to undergo reaction.
Correct answer is: Minimum energy required for reaction
Q.9 In the Arrhenius equation, k = Ae^(-Ea/RT), 'A' represents:
Activation energy
Pre-exponential factor
Gas constant
Temperature
Explanation - A is the frequency factor or pre-exponential factor representing collision frequency and orientation.
Correct answer is: Pre-exponential factor
Q.10 The integrated rate law for a first-order reaction is:
ln[A] = -kt + ln[A]₀
1/[A] = kt + 1/[A]₀
[A] = [A]₀ - kt
[A] = k[A]t
Explanation - Integrated first-order equation: ln[A] = ln[A]₀ - kt.
Correct answer is: ln[A] = -kt + ln[A]₀
Q.11 Which of the following affects the reaction rate but not the equilibrium position?
Catalyst
Temperature
Concentration
Pressure
Explanation - Catalyst speeds up the reaction but does not change the equilibrium composition.
Correct answer is: Catalyst
Q.12 The reaction 2NO + O₂ → 2NO₂ is experimentally found to be second-order with respect to NO and first-order with respect to O₂. Overall order is:
2
3
1
4
Explanation - Overall order = 2 + 1 = 3.
Correct answer is: 3
Q.13 The units of rate constant k for a zero-order reaction are:
M s⁻¹
s⁻¹
M⁻¹ s⁻¹
s
Explanation - For zero-order: rate = k, so k has units of concentration/time (M/s).
Correct answer is: M s⁻¹
Q.14 A catalyst:
Is consumed in reaction
Increases activation energy
Lowers activation energy
Changes equilibrium constant
Explanation - Catalysts provide an alternate pathway with lower activation energy without changing equilibrium.
Correct answer is: Lowers activation energy
Q.15 The reaction rate is fastest at:
Low temperature
High activation energy
High temperature
Low concentration
Explanation - Higher temperature increases kinetic energy of molecules, leading to more collisions and faster rate.
Correct answer is: High temperature
Q.16 Half-life of a second-order reaction depends on:
Initial concentration
Temperature only
Catalyst
Time only
Explanation - For second-order: t1/2 = 1/(k[A]₀), depends on initial concentration.
Correct answer is: Initial concentration
Q.17 Which factor does NOT influence the rate of reaction?
Nature of reactants
Temperature
Concentration
Color of container
Explanation - Color of the container generally has no effect on reaction rate unless photochemical.
Correct answer is: Color of container
Q.18 The slope of a ln[A] vs time graph for a first-order reaction gives:
Rate constant k
-k
1/k
Half-life
Explanation - Integrated first-order law: ln[A] = ln[A]₀ - kt, slope = -k.
Correct answer is: -k
Q.19 In chain reactions, an intermediate:
Is present in large amounts
Is consumed as quickly as it is formed
Does not participate in rate determination
Is always stable
Explanation - Chain reaction intermediates are highly reactive and exist only briefly.
Correct answer is: Is consumed as quickly as it is formed
Q.20 For the reaction A → B, the plot of 1/[A] vs time is linear. This indicates:
Zero-order reaction
First-order reaction
Second-order reaction
Third-order reaction
Explanation - For second-order: 1/[A] = kt + 1/[A]₀, giving a straight line in 1/[A] vs time plot.
Correct answer is: Second-order reaction
Q.21 The Arrhenius equation explains the effect of ______ on rate constant.
Concentration
Pressure
Temperature
Catalyst type
Explanation - Arrhenius equation: k = Ae^(-Ea/RT), shows k increases with temperature.
Correct answer is: Temperature
Q.22 Which type of reaction has a rate independent of concentration?
Zero-order
First-order
Second-order
Third-order
Explanation - Zero-order reactions have rate = k, independent of reactant concentration.
Correct answer is: Zero-order
Q.23 In the reaction 2A → B, if the rate = k[A]², the reaction is:
Zero-order
First-order
Second-order
Third-order
Explanation - Exponent in rate law with respect to A is 2, so overall order is 2.
Correct answer is: Second-order
Q.24 The rate constant of a reaction decreases with:
Increase in temperature
Decrease in temperature
Addition of catalyst
Increase in concentration
Explanation - Lower temperature reduces molecular collisions and kinetic energy, decreasing k.
Correct answer is: Decrease in temperature
Q.25 The reaction rate is directly proportional to the concentration of reactants in:
Zero-order
First-order
Second-order
Third-order
Explanation - For first-order: rate ∝ [A], directly proportional to reactant concentration.
Correct answer is: First-order