**Arrhenius Equation** (Temperature dependence of rate constant): Arrhenius developed a mathematical relationship between the rate constant (k) and temperature, called Arrhenius Equation. It may be represented as-

Where, A = Frequency factor, Ea = Activation energy, T = Absolute temperature, R = Gas constant

Taking logarithm of above equation, we get

It is clear that the value of activation energy, Ea increases and the value of k decreases, therefore, the reaction rate decreases.

**Calculation of activation energy from Arrhenius Equation**:

Ea and A can be determined by measuring the values of rate constant at two different temperature. Let k1 and k2 are the rate constant for the reaction at two different temperatures T1 and T2. Then,

**Activation Energy (Ea)**:

The minimum extra energy over and above the average potential energy of the reactants which must be supplied to the reactants to enable them to cross over energy barrier between reactants and products is called Activation Energy.

**Collision Theory:**

According to collision theory a chemical reaction take place due to collision between the particles of the reactants. The number of collisions that takes place per second per unit volume of the reacting mixture is known as collision frequency (Z).

The collisions which actually produce the products and therefore, result in the chemical reactions called effective collisions.

The main points of collision theory are summed up as-

1) For a reaction to occur there must be collisions between the reacting molecules.

2) Only certain fractions of the total number of collisions are effective in forming the products.

3) For effective collisions, the molecules should possess sufficient energy as well as

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