Reaction Kinetics Flashcards
What is the definition of the rate equation
The rate equation is defined as the mathematical expression that relates the rate of reaction with the concentrations of the reactants
What is a zeroth order of reaction
It is a reaction in which a reaction is independant of the concentrations of reactants
What is a first order reaction
It is a reaction in which the rate of reaction is directly proportional to the concentration of the reactants
What is a second order reaction
It is a reaction in which the rate of reaction is directly proportional to the product of the concentration of the reactants (A and B) or to the power of the concentration of one.
What is a psuedo first order reaction
It is a second order reaction that is approximately directly proportional to its reactants due to
(i) an excess of reactants
(ii) solvent is reactant
(iii) catalyst
as the concentrations of one of the reactants remain essentially the same
What is collision theory
It is the theory that states that a chemical reaction between reactants is undergone once
(i) collisions take place
(ii) reactants collide in the correct orientation
(iii) reactants possess activation energy
What is activation energy
It is the minimum amount of energy required for a reaction to undergo
What is the curve that illustrates the energy possessed by particles during a reaction
Maxwell-boltzmann curve
What is the significance if the maxwell-boltzmann curve
It shows the spread of kinetic energy of the particles
What are the five factors that determine rate of reaction
(i) physical state of reactants
(ii) concentration of reactants
(iii) tempearature of reactants
(iiii) catalyst
How does concentration affect the rate of reaction
An increase in concentration of reactants would lead to an increase in the number of reactants present in a given volume. This in turn leads to an increase in frequency of collisions and thus effective collisions. This causes a higher rate of reaction.
How does the physical state of the reactants affect the rate lf reaction
From solid to liquid to gas, an increase in the exposed surface area increases. This leads to more sites in which collisions can take place. As the frequency of effective collisions increase, the frequency of effective collisions increase and thus the rate of reaction increases
How does catalyst affect rate of reaction
The presence of a catalyst would lead to an alternative pathway of lesser energy for which the reaction can occur. As less activation energy is required, the fraction of reactants possessing sufficient kinetic energy would increase. This increases frequency of collisions, and thus frequency of effective collisions. This leads to an increase in rate of reaction
How does temperature affect rate of reaction
An increase in temperature would lead to an increase in kinetic energy of all particles. This causes an increase in the fraction of particles that possess kinetic energy equal to or more than the activation energy. This increases the frequency of effective collisions and hence the rate of reaction
Will a catalyst remain physically unchanged
No
Will a catalyst remain chemically unchanged
Yes
Are catalysts unique
Yes, each catalyst may only catalyse a certain class of reactions
What types of catalysts are there
(i) homogeneous
(ii) heterogeneous
(iii) auto-catalyst
(iiii) enzyme
What is a homogeneous catalyst
A homogeneous catalyst is a catalyst that is in the same phase as the reactants
Heterogeneous catalyst
A catalyst that is in a different phase from the reactants
How does a heterogeneous catalyst work
A heterogeneous catalysis occurs in this sequence of steps
- Adsorption of the reactants onto the active site on the surface of the catalyst
- Reaction at the surface of the catalyst
- Desorption of the reactants from the surface of the catalyst
What is adsorption during heterogeneous catalysis
During adsorption, chemical bonds of reactants are weakened (i) along with increasing the concentration of reactants after weak bonds are formed between the catalyst and reactants (ii)
This increases the rate of reaction as due to (i), activation energy is lower and due to (ii), a greater frequency of collisions are experienced
What is autocatalysis
It is a catalyst generated during the reaction itself
What is an enzyme
An enzyme is a biological catalyst and is very specific to a particular reaction they catalyse as they possess a special conformation for the three-dimensional active site such that the substrate molecule must have a matching shape to fit like a lock in a key
How does biocatalysis occur
- Substrate entering enzyme
- The enzyme and substrate slot together to form a complex
- The products formed
- Products leave enzyme
