CHEMICAL KINETICS

Question 1

What do you mean by chemical kinetics ?

Answer 1

Ans- The study of the speed or the rate of chemical reaction , the factors affecting the rates of the reactions and the mechanism by which the reaction proceed is known as chemical kinetics .

Question 2

Name the different types of reactions on the basis of rates .

Answer 2

Ans- very fast reaction

• very slow reaction
• reaction which are moderate

Question 3

What is the cause of instantaneous nature of ionic compound ?

Answer 3

The instantaneous nature of ionic reactions is due to the fact that these do not involve in breaking of bonds

Question 4

What do you mean by rate of reaction

Answer 4

The rate of reaction is the change in the concentration of any one of the reactants or products per unit time .

Question 5

Why do we use a minus sign in the equation of rate of reaction ?

Answer 5

The minus sign shows that the concentration of reactant is decreasing .

Question 6

What do you mean by average rate of reaction ?

Answer 6

Average rate of a reaction is the change in the concentration of any one of the reactants or the product and the time taken for that change to occur.

Question 7

What do you mean by instantaneous rate of reaction ?

Answer 7

It is the rate of reaction at any instant of time is the rate of change of concentration of any one of the reactant or product at that particular instant of time .

Question 8

What are the factors affecting the reaction rate ?

Answer 8

Ans - concentration of reactant

• temperature
• catalyst
• surface area of reactant

Question 9

What do you mean by rate law ?

Answer 9

The rate law is the expression in which reaction rate is given in terms of molar concentration of reactants with each term raised to some power ,which may or may not be same as the stoichiometric coefficient of the reacting species in a balanced chemical equation .

Question 10

What do you mean by rate constant ?

Answer 10

Rate constant may be defined as the rate of the reaction when the concentration of each reaction is taken as unity .

Question 11

What do you mean by order of reaction ?

Answer 11

The sum of the powers of the concentration of the reactants in the rate law expression is called the order of reaction .

Question 12

Name different types of order of reactions .

Answer 12

Ans- reaction of zero order

• reaction of first order
• reaction of second order
• reaction of fractional order

Question 13

What do you mean by molecularity of a reaction ?

Answer 13

The number of atoms , ios or molecules that must collide with one another simultaneouly so as to result in to a chemicaal reaction is calle dmolecularity of a reaction . they can be further divided into three :
unimolecular
dimolecular
trimolecular

Question 14

What do you mean by half life period ?

Answer 14

Half life period is the time in which half of the substance has reacted .

Question 15

What do you mean by pseudo first order reaction ?

Answer 15

It is a reaction which are not truly of first order but under certain conditions become reactions of first order are called pseudo - first order reactions.

Question 16

What do you mean by threshold energy ?

Answer 16

The minimum energy which the colliding molecules must have in order that the collision between them maybe effective is called threshold energy .

Question 17

What do you mean by activation energy ?

Answer 17

The minimum extra amount of energy absorbed by the reactant molecules so that their energy because equal to threshold value is called activation energy .

Question 18

State Arhenius equation ?

Answer 18

The effect of temperature on the rate of a reaction and hence on the rate constant k , was proposed by Arehenius equation .

Question 19

What is the use of catalyst ?

Answer 19

Ans - it increases the speed of reaction without itself undergoing any chemical change .

• basis of intermediate complex formation theory .
• intermediate compplex formed has much lower potential energy than the intermediate complex formed in absence of catalyst .
• presence of catalyst lowers the potential energy barrier and reaction follows a new alternate pathway which requires less activation energy .
• lower the activation energy , faster is the reaction .
• a catalyst does not alter Gibbs Energy .

Question 20

What is the collision theory of chemical reactions ?

Answer 20

The reactant molecules are assumed to be hard spheres and reaction is postulated to occur when molecules collide with each other .

Question 21

What do you mean by collision frequency ?

Answer 21

The number of collisions that take place per second per unit volume of reaction mixture is called collision frequency (Z) .