Chemical Kinetics TEXTBOOK Solution

4.1.For the reaction R—>P, the concentration of 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.

Answer :

NCERT Solutions For Class 12 Chemistry Chapter 4 Chemical Kinetics Textbook Questions Q1

4.2.In a reaction, 2A —-> Products, the concentration of A decreases from 0.5 mol L-1 to 0.4 molL-1 in 10 minutes. Calculate the rate during this interval?

Answer :

NCERT Solutions For Class 12 Chemistry Chapter 4 Chemical Kinetics Textbook Questions Q2

4.3. For a reaction, A + B → Products, the rate law is given by : r = k [A]1/2[B]2. What is the order of reaction?

Answer :

Rate law(r) = k [A]1/2[B]2

order of reaction = 12+2=212or2.5

4.4.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 ?

Answer :

The reaction is : X—>Y
According to rate law,
rate = k[X]2
If [X] is increased to 3 times, then the new rate is
rate’ = k[3X]2
rate’ = 9 k [X]2 = 9 rate
Thus, rate of reaction becomes 9 times and hence rate of formation of Y increases 9-times.

4.5. A first order reaction has a rate constant 1.15 x 10-3 s-1. How long will 5 g of this reactant take to reduce to 3 g?

Answer :

NCERT Solutions For Class 12 Chemistry Chapter 4 Chemical Kinetics Textbook Questions Q5

4.6.Time required to decompose SO2Cl2 to half of its initial amount is 60 minutes. If the decomposition is a first order reaction, calculate the rate constant of the reaction.

Answer :

For 1st order reaction,

NCERT Solutions For Class 12 Chemistry Chapter 4 Chemical Kinetics Textbook Questions Q6

4.7. What will be the effect of temperature on rate constant?

Answer :

In general, the rate constant for a reaction nearly becomes double with about 10° rise in temperature because of the fact that the effective collisions become almost double. The exact dependence of the reaction rate on temperature is given by Arrhenius equation; k=Ae−Ea/Rt.

Where A is the Arrhenius factor or the frequency factor. It is also called pre exponential factor. It is a constant specific to a particular reaction. R is gas constant and Ea is activation energy measured in joules/mole (J mol-1).

4.8.The rate of the chemical reaction doubles for and increase of 10 K in absolute temperature from 298 K. Calculate Ea.

Answer :

NCERT Solutions For Class 12 Chemistry Chapter 4 Chemical Kinetics Textbook Questions Q8

NCERT Solutions For Class 12 Chemistry Chapter 4 Chemical Kinetics Textbook Questions Q8.1

4.9.The activation energy for the reaction, 2 HI(g) —-> H2+I2 (g) is 209.5 k J mol-1 at 581 K.Calculate the fraction of molecules of reactants having energy equal to or greater than activation energy?

Answer :

Fraction of molecules having energy equal to or greater than activation energy is given by:

NCERT Solutions For Class 12 Chemistry Chapter 4 Chemical Kinetics Textbook Questions Q9