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(a) Rusting of iron

(c) mol L^-1s^-1

s^-1 is the unit of rate constant for a first order reaction.

The order of decomposition of acetaldehyde is 1.5.

1. increases 

2. collisions, rate 

3. lowered 

4. Pharmaco kinetics 

5. Paracetamol 

6. rate 

7. unity 

8. increased 

9. Pseudo first order reaction 

10. zero

(b) increase in the number of activated molecules

The order of the reaction is 4

(a) NO_(g) + O_3(g) → NO_3(g) + O_(g) Molecularity is 2.

Rate law : Rate = k [NO] x [O₃]

(b) H₂I_(g) + I_(g) → 2HI_(g) Molecularity is 2.

Rate law : Rate = k [H₂I] x [I]

(c) CI_(g) + Cl_(g) + N_2(g) → N_2(g) Molecularity is 3.

Rate law : Rate = k [Cl]²

Step I : Cl_(g) + O_3(g) → ClO_(g) + O_2(g) 

Step II : ClO_(g) + O_(g) → Cl(g) + O_2(g) 

(a) Overall reaction is obtained by adding both the reactions.

O_3(g) + O_(g) → 2O_2(g)

(b) Reaction intermediate is ClO_(g) which is formed in the first step and removed in the second step.

(c) Cl_(g) acts as a catalyst. It is an example of homo-geneous catalysis in which catalyst Cl_(g) forms an intermediate ClO_(g) and again is released in the second step.

(d) Since both the steps involve two reactants each, both the steps are bimolecular.

Given :

(1) NO_(g) + Cl_2(g) → NOCl_2(g) 

(2) NOCl_2(g) + NO_(g) → 2NOCl_(g)

(a) Overall reaction is obtained by adding both the reactions

2NO_(g) + Cl_2(g) → 2NOCl_2(g)

(b) The reaction intermediate is NOCl₂, since it is formed in first step and consumed in the second step.

(c) Since the first step is a slow and rate determining step, the molecularity is two.

Since the second step is a fast step its molecularity is not considered.

1. 2H₂O₂ + I^- → → H₂O +IO^-

H₂O₂ + IO- → H₂O + I^- + O₂

2. 2H₂O₂ + I^- → H₂O + IO^-

3. 2H₂O₂ + I^- → H₂O + IO^-

4. Order = 2

(i) NO_(g) + O_3(g) → NO_3(g) + O_(g)

(ii) NO_3(g) + O_(g) → NO_2(g) + O_2(g)

(a) The first step is slow and rate determining step since the rate depends on concentrations of NO_(g) and O_3(g). (Given : Rate = k [NO] x [O]) 

(b) The overall reaction is the combination of two steps.

NO_(g) + O_3(g) → NO_2(g) + O_2(g)

(c) NO_3(g) and O_(g) are reaction intermediates. They are formed in first step (i) and removed in the second step (ii).

Option : (b) Rate = \(-\frac{1}{2}\)\(\frac{d[X]}{dt}\) = \(-\frac{1}{3}\)\(\frac{d[Y]}{dt}\) = \(\frac{1}{4}\)\(\frac{d[Z]}{dt}\)

(a) The addition of two steps gives the overall reaction as

2NO_2(g) + F_2(g) → 2NO₂F_(g)

(b) Step (i) is slow. The rate law of the reaction is predicted from its stoichiometry. 

Thus, rate = k[NO₂] [F₂]

(c) F is produced in step 

(i) and consumed in step 

(ii) hence F is the reaction intermediate.

The number of reacting species taking part in an elementary reaction which must colloid simultaneously in order to bring about a chemical reaction is called molecularity of reaction. 

Zero order..

Mol/L/s is SI unit of rate constant of zero order reaction.

 (mol^)1-n . Ln^-1.s ^-1

Reactions taking place in more than one step are called complex reaction.

Order of reaction 

= 1/2 + 3/2 

 = 2

Sum of the powers of the concentration of the reactants in the rate equation is called order of reaction.

Rate constant is equal to rate of reaction when the product of the molar conc. of reactants is unity.

Expression in which reaction rate is given in terms of molar conc. 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.

Representation of rate of reaction in terms of concentration of reactants is called rate law. Rate expression and rate equation.

The characteristics of rate constant are as follows :

• The rate constant depends upon the nature of the reaction. 
• Higher the value of the rate constant, faster is the reaction. 
• Lower the value of the rate constant, slower is the reaction.
• By increasing the temperature, the magnitude of the rate constant increases. 
• For the given reaction, the rate constant has higher value in the presence of a catalyst than in the absence of the catalyst. 
• The reactions having lower activation energy have higher values for rate constants. 

(1) Pressure or conc. of reactants 

(2) temperature 

(3) catalyst.

(A) Rate constant : The rate constant of a chemical reaction is defined as the rate of the chemical reaction when the concentration (or active masses) of each reactant has unit value, i.e., 1 mol dm^-3 in the case of solution and the pressure is 1 atm in case of gases, e.g., for a reaction, 

A → products, Rate R = k[A].

If [A] = 1 mol dm^-3, then k = R.

(B) The rate constant of a reaction depends on the following factors :

• Nature of the reactants. 
• Temperature of the reaction. As the temperature increases, the velocity constant (rate constant) increases. 
• The conditions of the reactions like the presence of the catalyst, solvent, pH, etc. 
• It does not depend on the concentration of the reactants. But if one or more substances are in excess concentration, then the order of the reaction is independent of them. 

Order of a chemical reaction : The order of a chemical reaction is defined as the number of molecules (or atoms) whose concentrations influence the rate of the chemical reaction.

OR 

The order of a chemical reaction is defined as the sum of the powers (or exponents) to which the concentration terms of the reactants are raised in the rate law expression for the given reaction.

Explanation : 

Consider a reaction,

n₁A + n₂B → Products

Where n₁ moles of A react with n₂ moles of B.

The rate of this reaction can be expressed by the rate law equation as,

R = k [A]^n₁ [B]^n₂

Where k is the rate constant of the reaction, hence, the order of the reaction is n – n₁ + n₂, (observed, experimentally).

If n = 1, 

The reaction is called the first order reaction, 

If n = 2, 

It is called the second order reaction, etc.

If n = 0, 

It is called the zero order reaction.

e.g., photochemical reaction of H_2(g) and Cl_2(g).

The features of order of reaction are as follows :

• It represents the number of atoms, ions or molecules whose concentrations influence the rate of the reaction. 
• It is not related to the stoichiometric equation of the reaction, hence it cannot be predicted from stoichiometric balanced equation. 
• It is experimentally determined quantity. 
• It is defined only in terms of the concentrations of the reactants and not of products. 
• It may have values which are integers, fractional or zero. 
• Higher values are rare. Reactions of first and second order are in large number. Third order reactions are very few like, 2NO_(g) + Cl_2(g) → 2NOCl_(g). 

 The difference between instantaneous rate of reaction and averatge rate of a reaction are as Below

Pseudo-first-order reaction: The reaction which is bimolecular but order is one is called a pseudo-first order reaction. This happens when one of the reactants is in large excess. E.g., acidic hydrolysis of the ester (ethyl acetate). 

CH₃COOC₂H₅ +H₂O ------>  CH₃COOH + C₂H₅OH 

similarly inversion of cane sugar or hydrolysis of cane sugar is an example of pseudo first-order reaction.

According to the given equation, the rate of disappearance of reactant A is twice the rate of disappearance of reactant B.

Correct answer is

b. ClO₂^Θ

Correct answer is

d. 6 h

a. -k

Slope of the graph ln[A]_t versus t for first order reaction is -k.

c. 0

The order of the reaction for which the units of rate constant are mol dm^-3 s^-1 is 0.

Correct answer is

d. 3t

Correct answer is

b. 1

(a) The number of activated reactants increases.

(b) t_3/4 = 1.5 t_1/2

(c) The half life of reaction does not depend on initial concentration of reactants.

(a) mol L^-1 s^-1

The answer is (b) 1

(b) k = A e^-E_a/RT

(C) 3.3 times of half life

(II)—is 0.2; (III)—is 8 x 10^-2; (IV)—is 0.1

rate law = K [A] 

from I 2.0 × 10^-2 = K 0.1 

⇒ K = 2.0 × 10^-1min^-1 

from II 4 .0 × 10^-2 = 2 .0 × 10^-31 x 

⇒ K = 2 .0 × 10^-1 mol L^-1 

from III y = 2.0 × 10^-1 × 0.4 

⇒ y = 8 × 10^-2 mol 1L 

from IV 2.0 × 10^-2 = 2.0 × 10^-1 × z 

⇒ z = 0.1 mol L^-1