#### Chapters

Chapter 2: Solutions

Chapter 3: Electrochemistry

Chapter 4: Chemical Kinetics

Chapter 5: Surface Chemistry

Chapter 6: General Principles and Processes of Isolation of Elements

Chapter 7: The p-block Elements

Chapter 8: The d-block and f-block Elements

Chapter 9: Coordinate Compounds

Chapter 10: Haloalkanes and Haloarenes

Chapter 11: Alcohols, Phenols and Ethers

Chapter 12: Aldehydes, Ketones and Carboxylic Acids

Chapter 13: Amines

Chapter 14: Biomolecules

Chapter 15: Polymers

Chapter 16: Chemistry in Everyday Life

#### NCERT Chemistry Class 12

## Chapter 4: Chemical Kinetics

#### Chapter 4: Chemical Kinetics solutions [Pages 98 - 116]

For the reaction R → P, the concentration of a reactant changes from 0.03 M to 0.02 M in 25 minutes. Calculate the average rate of reaction using units of time both in minutes and seconds.

In a reaction, 2A → Products, the concentration of A decreases from 0.5 mol L^{−1} to 0.4 mol L^{−1} in 10 minutes. Calculate the rate during this interval?

For a reaction, A + B → Product; the rate law is given by, `r = k[A]^(1/2)[B]^2` . What is the order of the reaction?

The conversion of molecules X to Y follows second order kinetics. If concentration of X is increased to three times how will it affect the rate of formation of Y?

A first order reaction has a rate constant 1.15 10^{−3} s^{−1}. How long will 5 g of this reactant take to reduce to 3 g?

Time required to decompose SO_{2}Cl_{2} to half of its initial amount is 60 minutes. If the decomposition is a first order reaction, calculate the rate constant of the reaction.

What will be the effect of temperature on rate constant?

The rate of the chemical reaction doubles for an increase of 10 K in absolute temperature from 298 K. Calculate *E*_{a}.

The activation energy for the reaction 2HI_{(}_{g}_{)} → H_{2} + I_{2}_{(}_{g}_{) }is 209.5 kJ mol^{−1} at 581K. Calculate the fraction of molecules of reactants having energy equal to or greater than activation energy?

#### Chapter 4: Chemical Kinetics solutions [Pages 117 - 120]

From the rate expression for the following reactions, determine their order of reaction and the dimensions of the rate constants.

3 NO(g) → N_{2}O_{ }(g) Rate = *k*[NO]^{2}

From the rate expression for the following reactions, determine their order of reaction and the dimensions of the rate constants.

H_{2}O_{2 }(aq) + 3 I^{− }(aq) + 2 H^{+} → 2 H_{2}O (l) + `I_3^-` Rate = *k*[H_{2}O_{2}][I^{−}]

From the rate expression for the following reactions, determine their order of reaction and the dimensions of the rate constants.

CH_{3}CHO(g) → CH_{4}(g) + CO(g) Rate = *k *[CH_{3}CHO]^{3/2}

C_{2}H_{5}Cl(g) → C_{2}H_{4}(g) + HCl(g) Rate = k [C_{2}H_{5}Cl]

For the reaction: 2A + B → A_{2}B the rate = *k*[A][B]^{2} with *k* = 2.0 × 10^{−6} mol^{−2} L^{2} s^{−1}. Calculate the initial rate of the reaction when [A] = 0.1 mol L^{−1}, [B] = 0.2 mol L^{−1}. Calculate the rate of reaction after [A] is reduced to 0.06 mol L^{−1}.

The decomposition of NH_{3} on platinum surface is zero order reaction. What are the rates of production of N_{2} and H_{2} if *k *= 2.5 × 10^{−4} mol^{−1} L s^{−1}?

The decomposition of dimethyl ether leads to the formation of CH_{4}, H_{2} and CO and the reaction rate is given by

Rate = *k *[CH_{3}OCH_{3}]^{3/2} .The rate of reaction is followed by increase in pressure in a closed vessel, so the rate can also be expressed in terms of the partial pressure of dimethyl ether, i.e., `Rate = k(p_(CH_3OCH_3))^(3/2)`

If the pressure is measured in bar andtime in minutes, then what are the units of rate and rate constants?

Mention the factors that affect the rate of a chemical reaction.

A reaction is second order with respect to a reactant. How is the rate of reaction affected if the concentration of the reactant is **(i)** doubled **(ii)** reduced to half?

In a pseudo first order hydrolysis of ester in water, the following results were obtained:

t/s | 0 | 30 | 60 | 90 |

[Ester]mol L^{−1} |
0.55 | 0.31 | 0.17 | 0.085 |

**(i) **Calculate the average rate of reaction between the time interval 30 to 60 seconds.

**(ii) **Calculate the pseudo first order rate constant for the hydrolysis of ester.

A reaction is first order in A and second order in B. Write the differential rate equation.

A reaction is first order in A and second order in B. How is the rate affected on increasing the concentration of B three times?

A reaction is first order in A and second order in B. How is the rate affected when the concentrations of both A and B are doubled?

In a reaction between A and B, the initial rate of reaction (r_{0}) was measured for different initial concentrations of A and B as given below:

A/ mol L^{−1} |
0.20 | 0.20 | 0.40 |

B/ mol L^{−1} |
0.30 | 0.10 | 0.05 |

r_{0}/ mol L^{−1} s^{−1} |
5.07 × 10^{−5} |
5.07 × 10^{−5} |
1.43 × 10^{−4} |

What is the order of the reaction with respect to A and B?

The following results have been obtained during the kinetic studies of the reaction:

2A + B → C + D

Experiment | A/ mol L^{−1} |
B/ mol L^{−1} |
Initial rate of formation of D/mol L^{−1} min^{−1} |

I | 0.1 | 0.1 | 6.0 × 10^{−3} |

II | 0.3 | 0.2 | 7.2 × 10^{−2} |

III | 0.3 | 0.4 | 2.40 × 10^{−2} |

IV | 0.4 | 0.1 |

Determine the rate law and the rate constant for the reaction.

The reaction between A and B is first order with respect to A and zero order with respect to B. Fill in the blanks in the following table:

Experiment | A/ mol L^{−1} |
B/ mol L^{−1} |
Initial rate/mol L^{−1} min^{−1} |

I | 0.1 | 0.1 | 2.0 × 10^{−2} |

II | -- | 0.2 | 4.0 × 10^{−2} |

III | 0.4 | 0.4 | -- |

IV | -- | 0.2 | 2.0 × 10^{−2} |

Calculate the half-life of a first order reaction from their rate constants given below:

**(i)** 200 s^{−1} **(ii)** 2 min^{−1} **(iii)** 4 years^{−1}

The half-life for radioactive decay of ^{14}C is 5730 years. An archaeological artifact containing wood had only 80% of the ^{14}C found in a living tree. Estimate the age of the sample.

The experimental data for decomposition of N_{2}O_{5}

[`2N_2O_5 -> 4NO_2 + O_2`] in gas phase at 318K are given below:

t(s |
0 | 400 | 800 | 1200 | 1600 | 2000 | 2400 | 2800 | 3200 |

`10^2xx[N_2O_5]mol L^(-1)` | 1.63 | 1.36 | 1.14 | 0.93 | 0.78 | 0.64 | 0.53 | 0.43 | 0.35 |

**(i) **Plot [N_{2}O_{5}] against *t*.

**(ii) **Find the half-life period for the reaction.

**(iii)** Draw a graph between log [N_{2}O_{5}] and *t.*

**(iv) **What is the rate law?

**(v) **Calculate the rate constant.

**(vi) **Calculate the half-life period from *k *and compare it with (ii).

The rate constant for a first order reaction is 60 s^{−1}. How much time will it take to reduce the initial concentration of the reactant to its 1/16^{th} value?

During nuclear explosion, one of the products is ^{90}Sr with half-life of 28.1 years. If 1μg of ^{90}Sr was absorbed in the bones of a newly born baby instead of calcium, how much of it will remain after 10 years and 60 years if it is not lost metabolically.

For the decomposition of azoisopropane to hexane and nitrogen at 543 K, the following data are obtained.

t (sec) |
P(mm of Hg) |

0 | 35.0 |

360 | 54.0 |

720 | 63.0 |

Calculate the rate constant.

The following data were obtained during the first order thermal decomposition of SO_{2}Cl_{2} at a constant volume :SO_{2}Cl_{2} (g) → SO_{2} (g) + Cl_{2} (g)

Experiment | Time/s^{–1} |
Total pressure/atm |

1 | 0 | 0.5 |

2 | 100 | 0.6 |

Calculate the rate of the reaction when total pressure is 0.65 atm.

The rate constant for the decomposition of N_{2}O_{5} at various temperatures is given below:

T/°C |
0 | 20 | 40 | 60 | 80 |

10^5XXK/s^(-1) | 0.0787 | 1.70 | 25.7 | 178 | 2140 |

Draw a graph between ln *k *and 1/*T *and calculate the values of *A *and *E*_{a}. Predict the rate constant at 30º and 50ºC.

The rate constant for the decomposition of hydrocarbons is 2.418 × 10^{−5 }s^{−1} at 546 K. If the energy of activation is 179.9 kJ/mol, what will be the value of pre-exponential factor.

Consider a certain reaction A → Products with *k *= 2.0 × 10^{−2 }s^{−1}. Calculate the concentration of *A*remaining after 100 s if the initial concentration of *A *is 1.0 mol L^{−1}.

Sucrose decomposes in acid solution to give glucose and fructose according to the first order rate law. The half life of the reaction is 3 hours. Calculate fraction of sucrose which will remain after 8 hours.

The decomposition of hydrocarbon follows the equation *k *= (4.5 × 10^{11 }s^{−1}) e^{−28000 }^{K}^{/}^{T}

Calculate *E*_{a}.

The rate constant for the first order decomposition of H_{2}O_{2} is given by the following equation:

log *k *= 14.34 − 1.25 × 10^{4 }K/*T. *Calculate *E*_{a} for this reaction and at what temperature will its half-period be 256 minutes?

The decomposition of A into product has value of *k *as 4.5 × 10^{3} s^{−1} at 10°C and energy of activation 60 kJ mol^{−1}. At what temperature would *k *be 1.5 × 10^{4} s^{−1}?

The time required for 10% completion of a first order reaction at 298 K is equal to that required for its 25% completion at 308 K. If the value of *A *is 4 × 10^{10 }s^{−1}. Calculate *k *at 318 K and *E*_{a}.

The rate of a reaction quadruples when the temperature changes from 293 K to 313 K. Calculate the energy of activation of the reaction assuming that it does not change with temperature.

#### NCERT Chemistry Class 12

#### Textbook solutions for Class 12

## NCERT solutions for Class 12 Chemistry chapter 4 - Chemical Kinetics

NCERT solutions for Class 12 Chemistry chapter 4 (Chemical Kinetics) include all questions with solution and detail explanation. This will clear students doubts about any question and improve application skills while preparing for board exams. The detailed, step-by-step solutions will help you understand the concepts better and clear your confusions, if any. Shaalaa.com has the CBSE Chemistry Textbook for Class 12 solutions in a manner that help students grasp basic concepts better and faster.

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Concepts covered in Class 12 Chemistry chapter 4 Chemical Kinetics are Rate of a Chemical Reaction, Factors Influencing Rate of a Reaction, Half-life of a Reaction, Collision Theory of Chemical Reactions, Temperature Dependence of the Rate of a Reaction, Integrated Rate Equations - Introduction, Zero Order Reactions, First Order Reactions, Pseudo First Order Reaction, Effect of Catalyst on the Rate of Reaction, Kinetic Energy of Molecule, Role of Catalyst, Rate Law and Specific Rate Constant.

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