Find the molecularity of the reaction, Cl → 1 2 Cl 2 ( g ) . Give the potential energy diagram to explain activation energy.

Molecularity is defined as the number of reactants taking part in a chemical reaction. For the given reaction, Cl → 1 2 Cl 2 ( g ) , molecularity is one. Activation energy is required by reactants to form activated complexes and is equal to the difference between threshold energy and average kinetic energy. This can be explained by the following graph :

The decomposition of A into product has value 4 . 5 × 10 3 s - 1 at 10 ° C and energy of activation 60 kJ mol - 1 . At what temperature would it be 1 . 5 × 10 4 s - 1 ?

Given that, k 1 = 4 . 5 × 10 3 s - 1 , T 1 = 10 + 273 = 283 K k 2 = 1 . 5 × 10 4 s - 1 , E a = 60 kJ mol - 1 From logarithmic form of Arrhenius equation: log k 2 k 1 = E a 2 . 303 R T 2 - T 1 T 1 T 2 Substituting the values in the equation we get: log 1 . 5 × 10 4 4 . 5 × 10 3 = 6 . 0 × 10 4 2 . 303 × 8 . 314 T 2 - 283 283 T 2 ⇒ 0 . 5229 = 3133 . 62 T 2 - 283 283 T 2 ⇒ T 2 ≈ 297 K

The rate of 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.

Given that, T 1 = 293 K , T 2 = 313 K As the rate of reaction quadruples, i.e. k 2 = 4 k 1 From logarithmic form of Arrhenius equation at two different temperatures: log k 2 k 1 = E a 2 . 303 R T 2 - T 1 T 2 T 1 log 4 = E a 2 . 303 × 8 . 314 313 - 293 313 × 293 E a = 52854 . 5 J mol - 1 Therefore, the value of activation energy E a = 52 . 854 kJ mol - 1 .

You are required to determine the activation energy of a first order reaction, B → C How would you use these data to calculate E a graphically?

B → C is first order reaction The temperature dependence of the rate of a chemical reaction can be accurately explained by Arrhenius equation For activation energy K = Ae - E a / RT ⇒ E a = ( In A - In K ) RT We required A = frequency factor / Pre-exponential factor T (Temperature) and K (rate constant) at that temperature. Activation energy, E a can be calculated from the slope.

The rate constants for a first order reaction at various temperatures are as follows : K / s - 1 × 10 - 3 1 . 0 1 . 422 2 . 0 2 . 782 3 . 829 Temperature / ° C 25 30 35 40 45 Plot an appropriate graph of the data and calculate the energy of activation .

log K = log A - E a 2 . 303 RT log ( 1 × 10 - 3 ) = log A - E a 2 . 303 × R × 298 ....(i) log ( 1 . 42 × 10 - 3 ) = log A - E a 2 . 303 × R × 303 ....(ii) (ii)-(i) log 1 . 42 × 10 - 3 1 × 10 - 3 = E a 2 . 303 × R 1 298 - 1 303 log ( 1 . 422 ) × 2 . 303 × 8 . 314 = E a × 5 303 × 298 E a = 52 . 86 KJ InK = InA - E a RT y = c - mx

For the chemical reaction N 2 g + 3 H 2 g ⇋ 2 N H 3 g , the correct option is:

- d [ N 2 ] d t = 1 2 d [ N H 3 ] d t

- 1 3 d [ H 2 ] d t = - 1 2 d [ N H 3 ] d t

- d [ N 2 ] d t = 2 d [ N H 3 ] d t

3 d [ H 2 ] d t = 2 d [ N H 3 ] d t

HARD

12th Tamil Nadu Board

IMPORTANT

Earn 100

Define frequency factor ?

Important Questions on Chemical Kinetics

HARD

12th Tamil Nadu Board

IMPORTANT

Chemistry Crash Course (Based on Revised Syllabus-2023)>Chapter 7 - Chemical Kinetics>Exercise>Q 27

Find the molecularity of the reaction,

Cl \to \frac{1}{2} {Cl}_{2} (g)

. Give the potential energy diagram to explain activation energy.

HARD

12th Tamil Nadu Board

IMPORTANT

Chemistry Crash Course (Based on Revised Syllabus-2023)>Chapter 7 - Chemical Kinetics>Exercise>Q 28

The activation energy for the reaction $2 H I (g) \to H_{2} (g) + I_{2} (g)$ is $209.6 k J m o l^{- 1}$ at $581 K .$ Calculate the fraction of molecules of reactants having energy equal to or greater than activation energy?

EASY

12th Tamil Nadu Board

IMPORTANT

Chemistry Crash Course (Based on Revised Syllabus-2023)>Chapter 7 - Chemical Kinetics>Exercise>Q 29

Is the Frequency Factor temperature dependent?

HARD

12th Tamil Nadu Board

IMPORTANT

Chemistry Crash Course (Based on Revised Syllabus-2023)>Chapter 7 - Chemical Kinetics>Exercise>Q 30

The decomposition of

A

into product has value

4.5 \times 10^{3} s^{- 1}

10 ° C

and energy of activation

60 kJ {mol}^{- 1}

. At what temperature would it be

1.5 \times 10^{4} s^{- 1}

HARD

12th Tamil Nadu Board

IMPORTANT

Chemistry Crash Course (Based on Revised Syllabus-2023)>Chapter 7 - Chemical Kinetics>Exercise>Q 31

The rate of reaction quadruples when the temperature changes from

293 K

313 K

. Calculate the energy of activation of the reaction assuming that it does not change with temperature.

EASY

12th Tamil Nadu Board

IMPORTANT

Chemistry Crash Course (Based on Revised Syllabus-2023)>Chapter 7 - Chemical Kinetics>Exercise>Q 32

You are required to determine the activation energy of a first order reaction, $B \to C$

How would you use these data to calculate $E_{a}$ graphically?

HARD

12th Tamil Nadu Board

IMPORTANT

Chemistry Crash Course (Based on Revised Syllabus-2023)>Chapter 7 - Chemical Kinetics>Exercise>Q 33

The rate constants for a first order reaction at various temperatures are as follows

:

K / s^{- 1} \times 10^{- 3}

1.0

1.422

2.0

2.782

3.829

Temperature

/ ° C

25

30

35

40

45

Plot an appropriate graph of the data and calculate the energy of activation

.

HARD

12th Tamil Nadu Board

IMPORTANT

Chemistry Crash Course (Based on Revised Syllabus-2023)>Chapter 7 - Chemical Kinetics>Exercise>Q 34

Define the term activation energy. Using Arrhenius equation explain why the rate of reaction increases with increase in temperature.

Define frequency factor ?

Important Questions on Chemical Kinetics

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