Dependence of rate of reaction or rate constant on temperature

As the temperature increases, rate constant increases so rate of reaction also increases.

Collision frequency (Z):- Number of collisions taking place per second.

Threshold energy:- The minimum amount of energy possessed by reactant molecules so as to cross the energy barrier and get converted into products.

Activation energy:- The energy that must be supplied to the reactant molecules so that their energy becomes equal to threshold energy and the collisions b/w reactant molecules becomes effective i.e they get converted into products.

Threshold energy = Energy already possessed by reactants molecules + Activation energy (E_a)

Reaction profile:- A₂ + B₂ → 2 AB

Effect of temperature in terms of temperature coefficient

Temperature coefficient (n) = Rate constant at T + 10^oC / Rate constant at T

It is observed that rate of reaction becomes double or even more for energy 10^°C rise of temperature. So n = 2 to 3

There is no big change in collision frequency on raising the temperature. by 10^°C.

Z ∝ (T)^1/2        

Z = K (T)^1/2 

At 298 k, Z₁ = K (298)^1/2 

 

At 308 k, Z₂ = k (308)^1/2          So (Z₂/Z₁) = (308/298)^1/2  = 1.03

Z₂ = Z₁ x 1.03 

Actually the fraction of effective collisions becomes 2 to 3 times on increasing the temperature by 10^°C, Due to which rate of reaction becomes 2 to 3 times