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महाराष्ट्र राज्य शिक्षण मंडळएचएससी विज्ञान (सामान्य) इयत्ता १२ वी

Define activation energy. - Chemistry

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प्रश्न

Define activation energy.

Define the following term:

Activation energy

Define energy of activation of a reaction.

व्याख्या
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उत्तर १

Activation energy is the lowest energy necessary to commence a chemical reaction by disrupting the bonds of reactant molecules and creating the activated complex or transition state. It signifies the energy threshold that must be surmounted for a reaction to transpire. Activation energy is typically represented as Ea.

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उत्तर २

Activation energy may be defined as the excess energy that the reactant molecules (having energy less than the threshold energy) must acquire in order to cross the energy barrier and to change into the products.

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पाठ 4: Chemical Kinetics - REVIEW EXERCISES [पृष्ठ २५०]

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नूतन Chemistry Part 1 and 2 [English] Class 12 ISC
पाठ 4 Chemical Kinetics
REVIEW EXERCISES | Q 4.70 i. | पृष्ठ २५०
नूतन Chemistry Part 1 and 2 [English] Class 12 ISC
पाठ 4 Chemical Kinetics
REVIEW EXERCISES | Q 4.82 | पृष्ठ २५०
नूतन Chemistry Part 1 and 2 [English] Class 12 ISC
पाठ 4 Chemical Kinetics
REVIEW EXERCISES | Q 4.69 i. | पृष्ठ २५०
नूतन Chemistry Part 1 and 2 [English] Class 12 ISC
पाठ 4 Chemical Kinetics
VERY SHORT ANSWER TYPE QUESTIONS | Q 42. | पृष्ठ २६३

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संबंधित प्रश्‍न

The rate constant of a first order reaction increases from 4 × 10−2 to 8 × 10−2 when the temperature changes from 27°C to 37°C. Calculate the energy of activation (Ea). (log 2 = 0.301, log 3 = 0.4771, log 4 = 0.6021)


The rate constant for the first-order decomposition of H2O2 is given by the following equation:

`logk=14.2-(1.0xx10^4)/TK`

Calculate Ea for this reaction and rate constant k if its half-life period be 200 minutes.

(Given: R = 8.314 JK–1 mol–1)


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


The rate constant for the decomposition of N2O5 at various temperatures is given below:

T/°C 0 20 40 60 80
105 × k/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 Ea. 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 \[\ce{A -> Products}\] 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.


The decomposition of hydrocarbon follows the equation k = `(4.5 xx 10^11 s^-1) e^(-28000 K//T)`

Calculate Ea.


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.


In the Arrhenius equation for a first order reaction, the values of ‘A’ of ‘Ea’ are 4 × 1013 sec−1 and 98.6 kJ mol1 respectively. At what temperature will its half life period be 10 minutes?

[R = 8.314 J K1 mol1]


The rate constant of a first order reaction are 0.58 S-1 at 313 K and 0.045 S-1 at 293 K. What is the energy of activation for the reaction?


A first-order reaction is 50% completed in 40 minutes at 300 K and in 20 minutes at 320 K. Calculate the activation energy of the reaction. (Given : log 2 = 0·3010, log 4 = 0·6021, R = 8·314 JK–1 mol–1)


The decomposition of a hydrocarbon has value of rate constant as 2.5×104s-1 At 27° what temperature would rate constant be 7.5×104 × 3 s-1if energy of activation is  19.147 × 103 J mol-1 ?


Activation energy of a chemical reaction can be determined by ______.


Consider figure and mark the correct option.


Which of the following graphs represents exothermic reaction?

(a)  

(b)  

(c)  


During decomposition of an activated complex:

(i) energy is always released

(ii) energy is always absorbed

(iii) energy does not change

(iv) reactants may be formed


Which of the following statements are in accordance with the Arrhenius equation?

(i) Rate of a reaction increases with increase in temperature.

(ii) Rate of a reaction increases with decrease in activation energy.

(iii) Rate constant decreases exponentially with increase in temperature.

(iv) Rate of reaction decreases with decrease in activation energy.


Why does the rate of a reaction increase with rise in temperature?


Oxygen is available in plenty in air yet fuels do not burn by themselves at room temperature. Explain.


Thermodynamic feasibility of the reaction alone cannot decide the rate of the reaction. Explain with the help of one example.


Match the statements given in Column I and Column II

  Column I Column I
(i) Catalyst alters the rate of reaction (a) cannot be fraction or zero
(ii) Molecularity (b) proper orientation is not there always
(iii) Second half life of first order reaction (c) by lowering the activation energy
(iv) `e^((-E_a)/(RT)` (d) is same as the first
(v) Energetically favourable reactions (e) total probability is one are sometimes slow (e) total probability is one
(vi) Area under the Maxwell Boltzman curve is constant (f) refers to the fraction of molecules with energy equal to or greater than activation energy

What happens to most probable kinetic energy and the energy of activation with increase in temperature?


Total number of vibrational degrees of freedom present in CO2 molecule is


For an endothermic reaction energy of activation is Ea and enthalpy of reaction ΔH (both of there in KJ moI–1) minimum value of Ea will be ______.


In respect of the eqn k = \[\ce{Ae^{{-E_a}/{RT}}}\] in chemical kinetics, which one of the following statement is correct?


The activation energy in a chemical reaction is defined as ______.


The activation energy in a chemical reaction is defined as ______.


The slope of Arrhenius Plot `("In"  "k"  "v"//"s" 1/"T")` of first-order reaction is −5 × 103 K. The value of Ea of the reaction is. Choose the correct option for your answer. [Given R = 8.314 JK−1mol−1]


Arrhenius equation can be represented graphically as follows:

The (i) intercept and (ii) slope of the graph are:


Explain how and why will the rate of reaction for a given reaction be affected when the temperature at which the reaction was taking place is decreased.


A schematic plot of ln Keq versus inverse of temperature for a reaction is shown below

The reaction must be:


A first-order reaction is 50% complete in 30 minutes at 300 K and in 10 minutes at 320 K. Calculate activation energy (Ea) for the reaction. [R = 8.314 J K−1 mol−1]

[Given: log 2 = 0.3010, log 3 = 0.4771, log 4 = 0.6021]


It is generally observed that the rate of a chemical reaction becomes double with every 10°C rise in temperature. If the generalisation holds true for a reaction in the temperature range of 298 K to 308 K, what would be the value of activation energy (Ea) for the reaction?


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