p.1
Introduction to Chemical Kinetics
What is Chemical Kinetics?
The branch of chemistry that studies the rates of chemical reactions, factors affecting these rates, and the mechanisms by which reactions proceed.
p.6
Rate Law and Order of Reaction
What happens to the expression for k if the same reagent reacts with all reactants and products?
kt = ln (V0 / (2V0 - Vt))
p.10
Temperature Dependence and Activation Energy
What happens to the rate constant of a chemical reaction when the temperature rises by 10°?
The rate constant is nearly doubled.
p.8
Integrated Rate Equations
What method can be used to find the order of a reaction using concentration and time data?
Integrated rate equations.
p.7
Rate Law and Order of Reaction
What is the relationship between half-life and concentration in the Half Life Method?
Half-life is proportional to [A] raised to the power of (1-n).
p.9
Rate Law and Order of Reaction
Can the order of a reaction be zero or a fraction?
Yes, the order can be zero and even a fraction.
p.6
Rate Law and Order of Reaction
How can k be evaluated when titrating a reactant with a redox reagent?
kt = ln (V0 / Vt), where V0 is the initial volume and Vt is the volume at time t.
p.16
Molecularity and Mechanism of Reactions
How does the time required for the completion of three-fourths of a first order reaction compare to the time for half completion?
It is twice the time required for half completion.
p.10
Temperature Dependence and Activation Energy
What is the temperature coefficient in relation to the rate constant?
It is calculated as (Rate constant at T + 10°) / (Rate constant at T).
p.13
Rate Law and Order of Reaction
For the reaction X2 + 3Y2 → 2XY3, how is the rate of disappearance of Y2 expressed?
Rate = -1/3 d[Y2]/dt = 1/2 d[XY3]/dt.
p.1
Rate of a Chemical Reaction
How is the rate of a chemical reaction defined?
As the change in concentration of a reactant or product in unit time.
p.19
Integrated Rate Equations
Derive the integrated rate equation for a zero order reaction.
The integrated rate equation is [R] = -kt + [R]₀, where [R]₀ is the initial concentration.
p.8
Molecularity and Mechanism of Reactions
What is molecularity in a chemical reaction?
The number of reacting species that must collide simultaneously for a reaction to occur.
p.20
Rate Law and Order of Reaction
When can the order and molecularity of a reaction be the same?
When the rate determining step involves all the reactants in a one-step reaction.
p.8
Molecularity and Mechanism of Reactions
What are unimolecular reactions?
Reactions involving one reacting species, such as the decomposition of ammonium nitrite.
p.6
Rate Law and Order of Reaction
What does the variable 'x' represent in the context of the reaction?
The amount of reactant A that has reacted.
p.3
Rate Law and Order of Reaction
What does the constant 'k' represent in the rate equation?
'k' is the rate constant.
p.7
Rate Law and Order of Reaction
What is the Initial Rate Data Method used for?
To determine the order of a reaction by measuring initial rates at different concentrations.
p.6
Rate Law and Order of Reaction
What is the significance of checking 2-3 data points in the analysis?
To verify that the reaction is of first order.
p.9
Molecularity and Mechanism of Reactions
What are reaction intermediates?
Species formed during the course of a reaction that do not appear in the overall reaction.
p.21
Collision Theory of Chemical Reactions
What defines an effective collision?
Collisions where molecules collide with sufficient kinetic energy and proper orientation to break bonds and form products.
p.8
Factors Influencing Reaction Rate
What is the isolation method in determining reaction order?
Eliminating one reactant by taking it in excess to observe the effect of the other reactant on the rate.
p.1
Rate of a Chemical Reaction
What is the average rate of a reaction?
The rate of reaction measured over a definite time interval.
p.10
Temperature Dependence and Activation Energy
What is the significance of the area under the distribution curve?
The area remains constant since total probability must equal one at all times.
p.9
Molecularity and Mechanism of Reactions
What is molecularity?
The number of reacting species taking part in an elementary reaction that must collide simultaneously.
p.10
Temperature Dependence and Activation Energy
What does the Arrhenius equation describe?
The temperature dependence of the rate of a chemical reaction.
p.19
Rate Law and Order of Reaction
How is the half-life period of a first order reaction independent of initial concentration?
For a first order reaction, the half-life period is constant and given by t₁/₂ = 0.693/k, which does not depend on initial concentration.
p.8
Molecularity and Mechanism of Reactions
What defines bimolecular reactions?
Reactions that involve simultaneous collision between two species.
p.19
Rate Law and Order of Reaction
Under what condition can a bimolecular reaction be kinetically of first order?
A bimolecular reaction may be kinetically first order if one of the reactants is present in excess.
p.10
Temperature Dependence and Activation Energy
What is the relationship between temperature, activation energy, and reaction rate according to the Arrhenius equation?
Increasing temperature or decreasing activation energy results in an increase in the rate of the reaction.
p.2
Factors Influencing Reaction Rate
What factors influence the rate of a chemical reaction?
Concentration of reactants, temperature, and presence of a catalyst.
p.9
Rate Law and Order of Reaction
How is the order of a reaction defined?
It is the sum of the powers of the concentration of the reactants in the rate law expression.
p.10
Temperature Dependence and Activation Energy
What does the peak of the distribution curve represent in terms of molecular kinetic energy?
It represents the most probable kinetic energy possessed by the maximum fraction of molecules.
p.19
Rate of a Chemical Reaction
What are zero order reactions?
Zero order reactions are those where the rate of the reaction is proportional to the zero power of the concentration of reactants.
p.14
Rate Law and Order of Reaction
How do you calculate the overall order of a reaction?
The overall order is the sum of the powers of the concentration terms in the rate expression.
p.13
Rate Law and Order of Reaction
What is the definition of specific reaction rate or rate constant?
The rate of reaction when the molar concentration of each of the reactants is unity.
p.1
Rate of a Chemical Reaction
What is the instantaneous rate of a reaction?
The rate of change of concentration of any one of the reactants or products at a particular instant of time.
p.21
Temperature Dependence and Activation Energy
What is the relationship between the rate constant and temperature according to the Arrhenius equation?
log k = Constant - (E_a / (2.303RT)).
p.10
Temperature Dependence and Activation Energy
What does the plot of ln k vs 1/T yield?
A straight line with slope -Ea/R and intercept ln A.
p.20
Molecularity and Mechanism of Reactions
What is the molecularity of a reaction?
The number of reacting species that must collide simultaneously in an elementary reaction.
p.8
Molecularity and Mechanism of Reactions
What is a complex reaction?
A reaction that occurs through a sequence of elementary steps.
p.19
Molecularity and Mechanism of Reactions
What is meant by an elementary reaction?
An elementary reaction is a reaction that occurs in a single step.
p.22
Factors Influencing Reaction Rate
What happens to the rate constant (k) when the temperature changes from 300 K to 320 K?
The rate constant increases fourfold.
p.6
Rate Law and Order of Reaction
What is the relationship between pressure and the number of moles for gases?
Pressure (P) is proportional to the number of moles.
p.3
Rate Law and Order of Reaction
What is the characteristic of a first-order reaction?
The rate of the reaction is proportional to the first power of the concentration of the reactant.
p.15
Rate of a Chemical Reaction
What is the relationship between the new rate (r2) and the original rate (r1) in the given reaction?
r2 = 27 r1, meaning the rate becomes 27 times.
p.15
Rate of a Chemical Reaction
How is the rate of appearance of C calculated in the reaction 2A + B → 3C?
Rate = d[C]/dt = 1.3 × 10^(-4) mol L^(-1) s^(-1) / 3 = 0.43 × 10^(-4) mol L^(-1) s^(-1).
p.18
Integrated Rate Equations
What is the formula used to calculate the time for a first-order reaction?
t = (2.303/k) log([A]₀/[A]).
p.7
Integrated Rate Equations
In the context of the Half Life Method, what do V_0, V_t, and V_∞ represent?
V_0 is the initial volume, V_t is the volume at time t, and V_∞ is the volume at infinite time.
p.12
Integrated Rate Equations
What is the integrated rate law for an nth-order reaction?
1/[A]^(n-1) = 1/[A]₀ + kt
p.13
Rate Law and Order of Reaction
What are the units for the rate and the rate constant for the reaction Rate = k[A]^2[B]?
Units of rate = mol L⁻¹ s⁻¹; Units of k = L² mol⁻² s⁻¹.
p.5
Integrated Rate Equations
What is the integrated rate equation for a first order reaction?
0 [R] = 2.303 k log t + [R] at t = 1/2.
p.13
Rate of a Chemical Reaction
If the rate of disappearance of B is 1 × 10⁻² mol L⁻¹ s⁻¹, what is the rate of the reaction?
Rate = 0.5 × 10⁻² mol L⁻¹ s⁻¹.
p.20
Rate Law and Order of Reaction
Provide an example of a reaction and its order.
For NH4NO2 → N2 + 2H2O, the rate law is Rate = k[NH4NO2], so the order is 1.
p.13
Rate of a Chemical Reaction
What will be the rate of change in concentration of A and C if the rate of disappearance of B is known?
Rate of change in concentration of A will be 1 × 10⁻² mol L⁻¹ s⁻¹ and for C, it will be 1 × 10⁻² mol L⁻¹ s⁻¹.
p.10
Temperature Dependence and Activation Energy
How can the rate constants at two different temperatures be related using the Arrhenius equation?
By subtracting the equations for ln k at T1 and T2, leading to ln(k2/k1) = (Ea/R)(1/T1 - 1/T2).
p.5
Rate Law and Order of Reaction
In the reaction CH₃COOC₂H₅ + H₂O → CH₃COOH + C₂H₅OH, why can the concentration of water be considered constant?
Because the concentration of water does not change significantly during the reaction.
p.11
Rate Law and Order of Reaction
What is the Arrhenius equation?
k = Ae^(-Ea/RT), where k is the rate constant, A is the pre-exponential factor, Ea is the activation energy, R is the gas constant, and T is the temperature.
p.11
Rate of a Chemical Reaction
What is the formula for instantaneous rate of reaction?
Instantaneous Rate = -1/a (dA/dt) = -1/b (dB/dt) = 1/c (dC/dt) = 1/d (dD/dt).
p.13
Rate of a Chemical Reaction
What is meant by 'Rate of reaction'?
The change in the concentration of any one of the reactants or products per unit time.
p.7
Rate Law and Order of Reaction
What does the slope of the log(rate) vs log(concentration) graph represent?
The slope represents the order of the reaction (n).
p.1
Classification of Reactions by Rate
How are reactions classified based on their rates?
Reactions can be classified as very fast (e.g., precipitation of AgCl), very slow (e.g., rusting of iron), or moderate speed (e.g., hydrolysis of starch).
p.8
Rate Law and Order of Reaction
What indicates that the data fits into the first-order reaction equation?
If the rate constants calculated from multiple data points are equal.
p.15
Rate of a Chemical Reaction
What is the rate of disappearance of A in the reaction 2A + B → 3C?
Rate of disappearance of A = 2 * d[C]/dt = 0.86 × 10^(-4) mol L^(-1) s^(-1).
p.18
Rate Law and Order of Reaction
What does the variable [A] represent in the context of chemical kinetics?
[A] represents the concentration of the reactant at time t.
p.19
Rate Law and Order of Reaction
What is the half-life period of a reaction?
The half-life period is the time required for the concentration of a reactant to reduce to half of its initial concentration.
p.7
Rate Law and Order of Reaction
What is the significance of the polarimetric readings in the reaction involving sucrose?
They help in determining the concentration changes of glucose and fructose over time.
p.22
Factors Influencing Reaction Rate
How does the rate of a reaction change with temperature?
The rate of a particular reaction triples when the temperature changes from 50ºC to 100ºC.
p.5
Rate of a Chemical Reaction
What are pseudo first order reactions?
Reactions that are not truly first order but behave as such under certain conditions.
p.2
Rate Law and Order of Reaction
How is the overall order of a reaction determined?
By summing the exponents x and y in the rate law expression.
p.20
Molecularity and Mechanism of Reactions
What is an elementary step in a reaction?
Each step of a complex reaction is called an elementary step.
p.20
Rate of a Chemical Reaction
What is the rate of a reaction?
The change in the concentration of any of the reactants or products per unit time.
p.6
Rate Law and Order of Reaction
How can the ratio a/(a - x) be expressed in terms of pressure?
a/(a - x) = P∞ / (P∞ - Pt)
p.4
Rate of a Chemical Reaction
What is the definition of the half-life of a reaction?
The time in which the concentration of a reactant is reduced to one half of its initial concentration.
p.7
Rate Law and Order of Reaction
How does the Logarithmic Data Method help in determining reaction order?
By plotting log(rate) vs log(concentration), which yields a straight line with slope equal to the order of the reaction.
p.3
Rate of a Chemical Reaction
What happens to the concentration of R over time in a first-order reaction?
It exhibits exponential decay.
p.14
Rate Law and Order of Reaction
What is the rate expression for the reaction involving A and B?
Rate = k [A]^(1/2) [B]^(3/2)
p.13
Rate of a Chemical Reaction
Why does the instantaneous rate of reaction not change when a part of the reacting solution is taken out?
Because the instantaneous rate is measured over a very small interval of time.
p.9
Rate Law and Order of Reaction
How is the order of a complex reaction determined?
The order is given by the slowest step.
p.15
Rate Law and Order of Reaction
What is the definition of the rate of reaction?
The change in concentration of a reactant or product in a unit interval of time.
p.11
Effect of Catalysts on Reaction Rate
What is a catalyst?
A substance that alters the rate of a reaction without undergoing any permanent chemical change.
p.13
Rate Law and Order of Reaction
If the rate of decomposition of substance A becomes eight times when its concentration is doubled, what is the order of the reaction?
The order of the reaction is 3.
p.22
Temperature Dependence and Activation Energy
How do you calculate the rate constant at a different temperature using activation energy?
Using the Arrhenius equation: k = A e^(-Ea/RT)
p.15
Rate Law and Order of Reaction
What is the reaction rate constant (k)?
It is the rate of reaction when the molar concentration of each reactant is unity.
p.20
Rate Law and Order of Reaction
What is the order of a reaction?
The sum of the powers of the concentration of the reactants in the rate law expression.
p.8
Molecularity and Mechanism of Reactions
What is a rate determining step?
The slowest step in a reaction that controls the overall rate.
p.19
Rate Law and Order of Reaction
What is a pseudo first order reaction?
A pseudo first order reaction is one that is of higher order but follows first order kinetics under special conditions.
p.8
Molecularity and Mechanism of Reactions
What are elementary reactions?
Reactions that take place in one step.
p.19
Rate Law and Order of Reaction
Give an example of a pseudo first order reaction.
The acid hydrolysis of ethyl acetate is an example, represented by the rate equation Rate = k [CH₃ – COOC₂H₅].
p.14
Rate Law and Order of Reaction
What happens to the rate when both NO and Cl2 concentrations are doubled?
The rate becomes eight times.
p.5
Rate of a Chemical Reaction
How do we measure the progress of gaseous phase reactions?
By measuring the pressure of the gases or their volume.
p.5
Rate of a Chemical Reaction
What happens to the pressure of A as the reaction progresses?
The pressure of A decreases by x atm, while the pressures of B and C increase by x atm each.
p.6
Molecularity and Mechanism of Reactions
What type of reaction is represented by A (s) → B (s) + C (g)?
A solid reactant producing gaseous products.
p.8
Rate Law and Order of Reaction
How can the order of a reaction be calculated if simple observation is not possible?
By taking two data points and using logarithmic calculations.
p.13
Rate Law and Order of Reaction
How are the reaction expressions 2 d[H2]/dt and 3 d[NH3]/dt interrelated for the reaction N2(g) + 3H2(g) → 2NH3(g)?
3 d[NH3]/dt = -1/2 d[H2]/dt.
p.21
Collision Theory of Chemical Reactions
What is collision frequency?
The number of collisions per second per unit volume of the reaction mixture.
p.7
Integrated Rate Equations
What does the equation V_t = V_∞ - k * log(t) represent?
It represents the volume of a product formed at time t in relation to the volume at infinite time.
p.10
Temperature Dependence and Activation Energy
What happens to the distribution curve of molecular energies as temperature increases?
The maximum of the curve moves to a higher energy value and the curve spreads to the right.
p.21
Temperature Dependence and Activation Energy
What is the formula to calculate activation energy using rate constants at two different temperatures?
E_a = (R * T_1 * T_2 / (T_2 - T_1)) * log(k_2/k_1) / 2.303.
p.17
Rate Law and Order of Reaction
What is the relationship between the time required for 99.9% of a first order reaction and the time for half the reaction?
The time required for 99.9% of the reaction is about ten times that required for half the reaction.
p.7
Rate Law and Order of Reaction
What type of reactions can be analyzed using the Half Life Method?
Reactions where half-life can be measured at various concentrations.
p.20
Rate Law and Order of Reaction
When can the order and molecularity of a reaction be different?
When the reaction involves more than one step.
p.11
Effect of Catalysts on Reaction Rate
What is the role of the intermediate complex in catalysis?
Reactants combine with the catalyst to form an intermediate complex, which then decomposes to form products and regenerates the catalyst.
p.2
Rate of a Chemical Reaction
What is the overall rate expression for the reaction aA + bB → cC + dD?
Overall Rate = (–1/a) Δ[A]/Δt = (–1/b) Δ[B]/Δt = (+1/c) Δ[C]/Δt = (+1/d) Δ[D]/Δt.
p.1
Rate of a Chemical Reaction
How is the overall rate of a reaction defined when multiple reactants and products are involved?
By dividing the individual rates by their respective stoichiometric coefficients and equating their signs.
p.15
Rate Law and Order of Reaction
What does the slope of the graph represent in a zero order reaction?
The slope represents -d[R]/dt = k.
p.20
Molecularity and Mechanism of Reactions
Provide an example of a reaction and its molecularity.
For 2HI → H2 + I2, the molecularity is 2, as it involves simultaneous collision between two HI molecules.
p.14
Factors Influencing Reaction Rate
How does reducing the volume of the reaction vessel to one-third affect the rate of the reaction?
The rate increases due to higher concentration of reactants.
p.11
Rate of a Chemical Reaction
What is the formula for average overall rate of reaction?
Average Overall Rate = ΔD/dt = -ΔC/c dt = -ΔB/b dt = -ΔA/a dt.
p.20
Collision Theory of Chemical Reactions
What is threshold energy in a reaction?
The minimum energy required for reacting molecules to undergo effective collision leading to product formation.
p.1
Rate of a Chemical Reaction
What is the formula for calculating the average rate of reaction?
Average rate = (Decrease in concentration of R) / (Time taken) or (Increase in concentration of P) / (Time taken).
p.11
Effect of Catalysts on Reaction Rate
How does a catalyst affect activation energy?
It provides an alternate pathway by reducing the activation energy between reactants and products.
p.3
Integrated Rate Equations
What is the significance of the constant of integration 'I'?
It represents the initial concentration of the reactant.
p.1
Rate of a Chemical Reaction
Why is the rate of a reaction always positive?
Because the change in concentration of reactants is negative, it is multiplied by -1 to make the rate positive.
p.1
Rate of a Chemical Reaction
What are the units of the rate of a reaction?
Units are concentration time⁻¹, e.g., mol L⁻¹ s⁻¹ or atm s⁻¹ for gaseous reactions.
p.9
Temperature Dependence and Activation Energy
What is threshold energy?
The minimum energy required for colliding molecules to have an effective collision.
p.9
Temperature Dependence and Activation Energy
How does activation energy affect the speed of a reaction?
Less activation energy results in a faster reaction.
p.17
Integrated Rate Equations
How much time is required for 3/4 of PH3 to decompose?
Approximately 113.7 seconds.
p.14
Factors Influencing Reaction Rate
Will the order of the reaction change if the volume of the reaction vessel is diminished?
No, the order of the reaction remains the same.
p.5
Rate of a Chemical Reaction
What is the relationship between initial pressure and total pressure in a first order gas phase reaction?
pₜ = (pᵢ - x) + x + x = pᵢ + x.
p.9
Molecularity and Mechanism of Reactions
Can molecularity be zero or a non-integer?
No, molecularity cannot be zero or a non-integer.
p.10
Temperature Dependence and Activation Energy
What does the factor e^(-Ea/RT) in the Arrhenius equation represent?
The fraction of molecules that have kinetic energy greater than the activation energy (Ea).
p.9
Temperature Dependence and Activation Energy
What is activation energy?
The minimum extra amount of energy absorbed by reactant molecules to reach the threshold energy.
p.11
Effect of Catalysts on Reaction Rate
What are the important characteristics of a catalyst?
A small amount can catalyze a large amount of reactants, does not alter Gibbs energy, catalyzes spontaneous reactions, and does not change the equilibrium constant.
p.11
Collision Theory of Chemical Reactions
What does the Collision Theory state?
Reactions occur when reactant molecules collide with each other, and the rate depends on the number of effective collisions.
p.21
Temperature Dependence and Activation Energy
What is the activation energy for a reaction if the rate doubles between 295 K and 305 K?
Calculated using the Arrhenius equation based on the temperature change.
p.15
Rate Law and Order of Reaction
What is the order of the reaction if the concentration of reactant decreases linearly over time?
The reaction is of zero order.
p.2
Rate Law and Order of Reaction
What is the significance of the rate constant (k) in a rate law?
It is a proportionality constant that relates the rate of reaction to the concentrations of reactants.
p.17
Integrated Rate Equations
What fraction of the original amount of PH3 will remain undecomposed after 1 minute?
Approximately 0.25 or 25%.
p.2
Rate Law and Order of Reaction
Can the rate law for a reaction be predicted from the balanced chemical equation?
No, it must be determined experimentally.
p.2
Rate Law and Order of Reaction
What is the rate law expression for the reaction aA + bB → cC + dD?
Rate = k [A]^x [B]^y, where x and y are the reaction orders.
p.11
Collision Theory of Chemical Reactions
What factors affect the rate of reaction according to Collision Theory?
Energy factor (colliding molecules must have energy greater than threshold energy) and steric factor (proper orientations at the time of collision).
p.9
Temperature Dependence and Activation Energy
What is an activated complex?
An intermediate formed when reactant molecules absorb energy and cross the energy barrier.
p.19
Molecularity and Mechanism of Reactions
Provide an example of an elementary reaction.
The reaction between H₂ and I₂ to form 2HI is an example of an elementary reaction.
p.20
Temperature Dependence and Activation Energy
What is the Arrhenius equation?
k = A e^(-Ea/RT), where A is the frequency factor, R is the gas constant, and Ea is the activation energy.
p.22
Temperature Dependence and Activation Energy
How is the activation energy calculated when the rate constant increases fourfold?
Using the equation: Ea = -R(T2-T1) log(k2/k1) / (T1*T2)
p.2
Integrated Rate Equations
What characterizes a zero-order reaction?
The rate of the reaction is proportional to the zero power of the concentration of reactants.
p.20
Rate Law and Order of Reaction
Distinguish between order and molecularity of a reaction.
Order is the sum of powers in the rate law and can be zero or fractional; molecularity is the number of species in an elementary reaction and cannot be zero or non-integer.
p.2
Rate Law and Order of Reaction
What is the order of a reaction if the rate law is Rate = k [A]² [B]¹?
The overall order is 3 (2 + 1).
p.6
Rate Law and Order of Reaction
What is the expression used to find the rate constant k for a first-order reaction?
k = (1/t) ln [P∞ / (P∞ - Pt)]
