What is the activation energy and how to different from threshold energy ?

Threshold Energy and Activation Energy:

Threshold energy(THE): For a reaction to take place the reacting molecules must colloid together, but only those collisions, in which colliding molecules possess certain minimum energy is called threshold energy (THE or ET) or the total minimum energy that reacting species must possess in order to undergo effective collision to form product molecules is called threshold energy.

Activation energy (Ea): It is extra energy which must be possessed by reactant molecules so that collision between reactant molecules is effective and leads to formation of product molecules.

ET =Threshold Energy, (THE)

HR = Enthalpy or Energy or Potential of reactants.

HP = Enthalpy or Energy or Potential of product,

(Ea)f =Activation energy for forward reaction.

(Ea)b =Activation energy for backward reaction.

Activated complex: It is formed between reacting molecules which is highly unstable and readily changes into product.

what happen when activation energy of a chemical reaction becomes equal to RT?

“It means if Ea=RT then rate constant become about 37% of the Arrhenius constant.

The energy of activation for a reaction is 100 kJ mol–1. Presence of a catalyst lowers the energy of activation by 75%.What will be effect on rate of reaction at 20ºC, other things being equal?

SOLUTION: The Arrhenius equation is

In Arrhenius equation for a certain reaction, the value of A and Ea (activation energy) are 4 × 10^13 sec–1 and 98.6 kJ mol–1 respectively. At what temperature, the reaction will have specific rate constant 1.1 × 10^–3 sec–1?

SOLUTION: According to Arrhenius equation

Cu64 (Half life=22.8 hours) decay by beta emission (38%), beta+ emission (19%) and electron capture (43%). write the decay product and calculate Half lives for each of the decay process. [IIT 2002]

SOLUTION:  

(1):

 (2)  Above are parallel reactions occurring from Cu⁶⁴   

T₁ T₂ and T₃ are the corresponding partial half lives and also K= K₁ + K₂ + K₃ (for parallel reaction)