Reaction Kinetics

Question 1

What is the definition of the rate equation

Answer 1

The rate equation is defined as the mathematical expression that relates the rate of reaction with the concentrations of the reactants

Question 2

What is a zeroth order of reaction

Answer 2

It is a reaction in which a reaction is independant of the concentrations of reactants

Question 3

What is a first order reaction

Answer 3

It is a reaction in which the rate of reaction is directly proportional to the concentration of the reactants

Question 4

What is a second order reaction

Answer 4

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.

Question 5

What is a psuedo first order reaction

Answer 5

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

Question 6

What is collision theory

Answer 6

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

Question 7

What is activation energy

Answer 7

It is the minimum amount of energy required for a reaction to undergo

Question 8

What is the curve that illustrates the energy possessed by particles during a reaction

Answer 8

Maxwell-boltzmann curve

Question 9

What is the significance if the maxwell-boltzmann curve

Answer 9

It shows the spread of kinetic energy of the particles

Question 10

What are the five factors that determine rate of reaction

Answer 10

(i) physical state of reactants
(ii) concentration of reactants
(iii) tempearature of reactants
(iiii) catalyst

Question 11

How does concentration affect the rate of reaction

Answer 11

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.

Question 12

How does the physical state of the reactants affect the rate lf reaction

Answer 12

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

Question 13

How does catalyst affect rate of reaction

Answer 13

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

Question 14

How does temperature affect rate of reaction

Answer 14

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

Question 15

Will a catalyst remain physically unchanged

Answer 15

No

Question 16

Will a catalyst remain chemically unchanged

Answer 16

Yes

Question 17

Are catalysts unique

Answer 17

Yes, each catalyst may only catalyse a certain class of reactions

Question 18

What types of catalysts are there

Answer 18

(i) homogeneous
(ii) heterogeneous
(iii) auto-catalyst
(iiii) enzyme

Question 19

What is a homogeneous catalyst

Answer 19

A homogeneous catalyst is a catalyst that is in the same phase as the reactants

Question 20

Heterogeneous catalyst

Answer 20

A catalyst that is in a different phase from the reactants

Question 21

How does a heterogeneous catalyst work

Answer 21

A heterogeneous catalysis occurs in this sequence of steps

1. Adsorption of the reactants onto the active site on the surface of the catalyst
2. Reaction at the surface of the catalyst
3. Desorption of the reactants from the surface of the catalyst

Question 22

What is adsorption during heterogeneous catalysis

Answer 22

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

Question 23

What is autocatalysis

Answer 23

It is a catalyst generated during the reaction itself

Question 24

What is an enzyme

Answer 24

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

Question 25

How does biocatalysis occur

Answer 25

1. Substrate entering enzyme
2. The enzyme and substrate slot together to form a complex
3. The products formed
4. Products leave enzyme