The simple Collision Theory assumes that molecules are hard spheres and ignores the structural aspect, particularly the proper orientation required for reaction.

For a zero-order reaction, t1/2=[R]0/2kt_{1/2} = [R]_0 / 2kt1/2​=[R]0​/2k, meaning it is directly proportional to the initial concentration of the reactant.

A reaction with a molecularity of three is called termolecular.

The rate measured over a specific, finite time period is called the Average Rate of Reaction.

In a zero-order reaction, the rate is constant and independent of the reactant concentration. Thus, concentration decreases linearly with time.

The Arrhenius Equation is the mathematical relationship showing how the rate constant varies with temperature.

k is the proportionality constant known as the Rate Constant (or specific reaction rate).

For a first-order reaction, t1/2t_{1/2}t1/2​ is independent of initial concentration and given by t1/2=0.693/kt_{1/2} = 0.693/kt1/2​=0.693/k.

Since Ea,forward​>Ea,reverse​, the energy of products is lower than the energy of reactants, meaning the reaction is exothermic (ΔH is negative).

Such reactions appear to be of higher order but behave as first order because the concentration of one reactant (water) remains effectively constant, classifying it as a Pseudo First Order reaction.

P is the probability factor or Steric Factor, which accounts for the necessary proper orientation of molecules during collision.

The rate constant is a specific value for a reaction at a given temperature and is independent of the initial concentration of reactants.

Raising the temperature significantly increases the fraction of molecules that possess energy equal to or greater than the Activation Energy.

Collision Theory is based on the premise that reacting molecules must collide with each other to undergo chemical change.

Integrated rate equations are used to find the concentration of reactants at a certain time or to determine the rate constant.

The order is the sum of the exponents in the experimentally determined Rate Law (Rate Expression).

A catalyst provides a new mechanism, thereby lowering the Ea but leaving the initial and final energy states (and thus ΔG) unchanged.

Molecularity is defined as the number of reacting species (atoms, ions, or molecules) participating in an elementary reaction.

The correct form of the integrated rate law for a first-order reaction is ln[R]=−kt+ln[R]0​ (or similar logarithmic expressions).

For a collision to lead to a reaction, the molecules must have energy >Ea and also have the proper orientation, defined by the Steric Factor (P).

Molecularity applies only to elementary steps, while Order can be fractional or zero and is determined experimentally for the overall reaction.

Reaction rate is measured as change in concentration (moles/L or M) over change in time (seconds), giving units of mol L⁻¹ s⁻¹.

Rate ∝ [A]². Doubling [A] leads to 2² = 4 times the rate.

A catalyst increases the rate by providing an alternative reaction pathway with a lower Activation Energy.

Collision Frequency Z is defined as the number of collisions taking place per second per unit volume of the reaction mixture.

Ea is the Activation Energy, the minimum excess energy required by reacting molecules to undergo effective collision.

Threshold Energy is the minimum energy required for an effective collision, which is the sum of the average energy of reactants and the activation energy.

The Rate Expression mathematically links the rate of reaction to the concentration of reactants.

The rate at a particular moment is the Instantaneous Rate, which is determined by drawing a tangent to the concentration vs. time plot.

Rate= – 1/2 d[A]/dt = +1/1 d[B]/dt Therefore, the rate of disappearance of A is twice the rate of formation of B.