Chemical kinetics

Question 1

Reaction rate depends on

Answer 1

Physical state of reactants
Temperature
Pressure
Concentration of reactants
Catalysts
Intensity of light and radiation

Question 2

Ionic vs covalent reactions

Answer 2

Ionic reactions are usually fast reactions. Ionic compounds completely ionises in aqueous medium. No bonds break down during the reaction.

Covalent reactions are usually slow. Reactions involves in several bond breaking and forming.

Question 3

Reaction rate definition and unit

Answer 3

Rate of reaction is the change of the amount of reactant or product per unit time

mol s-1

Question 4

Why does Zn powder has a greater reaction rate than Zn granules

Answer 4

High surface area
High frequency of collisions
High rate of reaction

Question 5

Properties of a catalyst

Answer 5

Do not change the percentage yield of a reaction
Only a small concentration will be needed
Do not get consumed during the reaction
Can regenerate at the end of the reaction
Lowers the activation energy
Do not change the enthalpy of a reaction
Do not disrupt the equilibrium position of a reaction

Question 6

Which elements of the periodic table acts as catalysts

Answer 6

Most of the d block elements and their oxides

Question 7

Rate constant or velocity constant depends on

Answer 7

Concentration
Time
Order of reaction

Question 8

Basic requirements for a reaction to proceed

Answer 8

Reactant molecules should collide with each other
Molecular collisions should have a properly defined orientation
Properly oriented molecular collisions should exceed certain values of energy during a collision (activation energy)

Question 9

Characteristics of zero order reactions

Answer 9

Reaction rate is independent of the initial concentration of reactant and is equal to the rate constant

Question 10

If the initial concentration of A is much greater than the other reactant B, how does this affect on the reaction rate

Answer 10

Since the initial concentration of A is much greater than the B, it does not affect the reaction rate is not expressed in the rate law of the reaction

Question 11

If the rate does not change when the concentration of the reactants is changed, the order of the reaction is

Answer 11

Zero order

Question 12

If the rate doubles when the concentration of the reactants is doubled, the order of the reaction is

Answer 12

First order

Question 13

If the rate quadruples when the concentration of the reactants is doubles, the order of the reaction is

Answer 13

Second order

Question 14

Half life of a first order reaction =

Answer 14

0.693 / k
k = rate constant

Question 15

Half life of a zero order reaction =

Answer 15

initial concentration of reactants / 2k
k = rate constant

Question 16

Elementary reactions, unimolecular and bimolecular reactions

Answer 16

A chemical reaction taking place in only in 1 step is known as elementary reactions

Unimolecular elementary reactions are the reactions involving via 1 step involving in only 1 species of reactants

In an elementary reaction the order of reactants is equal to the stoichiometric coefficient

Question 17

The overall rate of a reaction is controlled by which step

Answer 17

rate of the slowest step hence it is known as the rate determining step

Question 18

Types of elementary reactions

Answer 18

Unimolecular
Bimolecular
Termolecular

More than 3 molecules cannot be seen in an elementary reactions and these kind of reactions occurs through multistep reactions

Question 19

Transition state

Answer 19

A species with partial bonds exists that is neither a reactant nor a product. Exists only at the highest potential.