WorksheetsChemical Kinetics
Total questions: 50
Worksheet time: 25mins
For a first-order reaction with a half-life of 30 minutes, what fraction of reactant remains after 90 minutes?
1/2
1/4
1/8
1/16
For a second-order reaction, if the initial concentration is doubled, how does the half-life change?
Halves
Doubles
Remains constant
Quadruples
The unit of rate constant for a second-order reaction is:
L mol⁻¹ s⁻¹
M⁻¹ s⁻¹
(mol/L)⁻¹ s⁻¹
All the above
For a first-order reaction with a rate constant k=0.693 min−1, what is its half-life?
1min
2min
3min
4min
For a zero-order reaction with a rate constant k=0.1 mol/L/s, how long will it take for the concentration to decrease from 0.5 mol/L to 0.2 mol/L?
3 sec
5 sec
10 sec
12 sec
The overall order of a reaction is defined as:
The sum of the stoichiometric coefficients
The sum of the exponents in the rate law expression.
The maximum number of molecules involved in any elementary step.
None of these
The transition state in a reaction is characterized by:
Maximum potential energy along the reaction coordinate.
Minimum potential energy along the reaction coordinate
Equal potential energy as reactants and products
None of the above
In transition state theory, what does ΔG‡ represent?
Free energy of reactants
Free energy of products
Free energy of activated complex
None of the above
In a reaction mechanism, if the first step is slow and the second step is fast, what can be inferred about the overall rate law?
It depends on both steps.
It depends only on the fast step
It depends only on the slow step.
It cannot be determined
According to collision theory, which of the following factors affects the rate of reaction?
Concentration of reactants
Temperature
Presence of a catalyst
All of the above
For the reaction 2A+B→C, if the rate law is Rate=k[A]2, the molecularity and order are:
3, 2
2, 3
3, 3
2, 2
For a second-order reaction, if 1/[A] vs. t has a slope of 0.02 L/mol/s, the rate constant is:
0.02 L/mol/s
0.04 L/mol/s
0.01 L/mol/s
0.05 L/mol/s
For the reaction mechanism:
Step 1: A+B→C (slow)
Step 2: C→D (fast)
The rate law is:
Rate =k[A][B]
Rate =k[C]
Rate =k[A]2[B]
Rate =k[D]
The activation energy for the forward reaction is Ea, and the enthalpy change (ΔH) is −40 kJ/mol. What is the activation energy for the backward reaction?
Ea + 40 kJ/mol
Ea - 40 kJ/mol
40 kJ/mol
Ea
The half-life for a zero-order reaction is proportional to:
Initial concentration
Rate constant
(Initial concentration)2
Temperature
The rate of reaction is doubled when the concentration of a reactant is doubled. The order of the reaction with respect to this reactant is:
0
1
2
3
The unit of the rate constant for a zero-order reaction is:
mol L⁻¹ s⁻¹
L mol⁻¹ s⁻¹
mol⁻² L² s⁻¹
s⁻¹
If the temperature of a reaction is increased from 300K to 310K and the rate doubles, the activation energy of the reaction is approximately
52 kJ/mol
62 kJ/mol
100 kJ/mol
65 kJ/mol
Which of the following statements about the Arrhenius equation is correct?
The rate constant increases with decreasing activation energy.
The rate constant decreases with increasing temperature.
The rate constant is independent of temperature.
The activation energy has no effect on the rate constant.
The half-life of a first-order reaction is 10 minutes. What is the time required for 75% of the reactant to decompose?
10min
20min
30min
40 min
Which of the following statements is incorrect?
Molecularity is always a whole number.
Order of a reaction can be zero
Molecularity is determined experimentally
Order can be fractional
A catalyst increases the rate of a reaction by:
Increasing activation energy
Increasing the energy of reactants
Providing an alternative pathway with lower activation energy
Increasing temperature
According to the collision theory, for a reaction to occur:
Reacting molecules must collide with sufficient energy and proper orientation
Reacting molecules must collide with low energy
The reaction must be exothermic
The reaction must be endothermic
If a reaction is first order in A and zero order in B, the rate law can be written as:
Rate = k[A]
Rate = k[A][B]
Rate = k[B]
Rate = k[A]⁰[B]
The half-life of a first-order reaction is independent of:
Temperature
Activation energy
initial concentration
Reaction mechanism
If the half-life of a first-order reaction is 20 min, the time required for 87.5% decomposition is:
20 min
40 min
60 min
80 min
For a zero-order reaction, the concentration-time graph is:
A straight line with a positive slope
A straight line with a negative slope
A curve with increasing slope
A curve with decreasing slope
In the Arrhenius equation k = A e^(-Ea/RT), "A" represents:
Activation energy
Rate constant
Frequency factor
Temperature
The graph of ln k vs. 1/T is:
Linear with a negative slope
Linear with a positive slope
Parabolic
Exponential
The slowest step in a reaction mechanism determines the:
Overall rate of reaction
Activation energy
Products formed
Reaction order
The fraction of molecules with energy equal to or greater than activation energy is given by:
Arrhenius equation
Collision theory
Van't Hoff equation
Henry's law
In an exothermic reaction, the activation energy for the forward reaction is:
Greater than reverse reaction
Less than reverse reaction
Equal to reverse reaction
Zero
The rate law for a third-order reaction could be:
Rate = k[A]²[B]
Rate = k[A][B][C]
Rate = k[A]³
All of the above
When the temperature increases, the rate of reaction:
decreases
Increases
Remains constant
Is unpredictable
A reaction with a negative activation energy suggests:
Spontaneous reaction
Endothermic reaction
A complex mechanism
Unusual behavior
The slope of a ln k vs. 1/T plot is:
+ Ea/R
- Ea/R
ln A
ln Ea
A reaction follows the rate law Rate = k[A][B]. What happens to the rate when [A] is doubled and [B] is tripled?
Increases 2 times
Increases 3 times
Increases 6 times
Unchanged
The rate of a reaction depends on:
Temperature
Reactant concentration
Presence of catalyst
All of the above
The rate constant of a reaction depends on
Temperature
Reactant concentration
Presence of catalyst
All of the above
If the concentration of reactant is doubled in a zero-order reaction, the rate will:
Remain same
Double
Become four times
Decrease
Which of the following is incorrect?
Rate of reaction is directly proportional to reactant concentration
Order of reaction is always an integer
Molecularity is determined by reaction mechanism
The rate constant has different units for different orders of reaction
If the rate constant of a first-order reaction is 0.693 min⁻¹, the half-life is:
0.1 min
1 min
10 min
100 min
The activation energy of a reaction can be determined from:
Arrhenius equation
Rate law
Molecularity
Stoichiometry
The rate constant increases with increasing temperature because:
More molecules have energy greater than activation energy
Activation energy increases
Concentration increases
Catalyst is used
The collision frequency increases when:
Temperature increases
Reactant concentration increases
Both (A) and (B)
None
The unit of rate constant for a third-order reaction is:
mol L⁻¹ s⁻¹
L mol⁻¹ s⁻¹
L² mol⁻² s⁻¹
s⁻¹
For a zero-order reaction, half-life is given by:
t1/2= K0.693
t1/2= 2K[A]0
t1/2= K[A]01
t1/2= K[A]0
The half-life of a first-order reaction is 10 minutes. How much time is required for the reactant concentration to decrease to 25% of its initial value?
10 minutes
20 minutes
30 minutes
40 minutes
Which of the following best describes the role of a catalyst in a chemical reaction?
It increases the activation energy, thereby increasing the reaction rate.
It provides an alternative reaction pathway with a lower activation energy.
It increases the equilibrium constant of the reaction.
It gets consumed in the reaction and does not regenerate.
Which type of catalyst is used in the Haber process for ammonia synthesis?
Pt
Fe
Ni
Cu
