Chemical kinetics involves studying the rate of chemical reactions by examining changes in concentration over time. The rate of a reaction depends on factors like temperature, catalysts, and activation energy. Reaction rates can be expressed using rate laws and rate constants, with the order of a reaction defined as the sum of the exponents of the concentration terms in the rate expression. Common reaction orders include zero order, first order, and second order reactions.

1. Chemical Kinetics
SUBMITTED BY ISHU GARG,
UNIVERSITY ROLL NUMBER- 19010700500035
SUBMITTED TO DR. NEELAM SING
SUBJECT PHYSCIAL PHARMACEUTICS CODE 403T

2. INTRODUCTION
 Chemical kinetics involves the study of the rate of a chemical reaction.
 The rate of a reaction can be understood by studying the time course of changes in the
concentration.
 Chemical kinetics is related to drug stability, dissolution, drug release in biological system,
drug pharmacokinetics i.e., metabolism and excretion, and drug action.
 RATE OF REACTION- Rate of reaction is defined as the rate at which reaction occurs i.e.,
product formation. In case of multiple step reaction the slowest step (step with effective
collision) is the rate determining step.
 Collision theory explains that the effective collision brings the product formation. The
number of collisions per second per unit volume of the reaction mixture is known as collision
frequency-Z.

3.  Hence for a general reaction,
A+B product AB
Rate= ZAB 𝑒−𝐸𝑎/𝑅𝑇
Now including the probability or stearic factor P
Rate= PZAB 𝑒−𝐸𝑎/𝑅𝑇
,Ea= Activation energy
R= Universal gas constant
T= temperature

4. Rate expression and rate constant
 For a reaction, aA + bB cC + dD
Rate α [𝐴]𝑥] [𝐵]𝑦
x,y may or may not be equal to stoichiometric coefficient.
Rate = K [𝐴]𝑥
] [𝐵]𝑦
−
𝑑[𝑅]
𝑑𝑡
= K [𝐴]𝑥
] [𝐵]𝑦
,where K is the Rate constant
 Rate constant α temperature and catalyst.
 Rate law is reaction expressed in terms of molar concentration of reactants with each term
raised to some power.

5. Order of reaction
 Defined as the number of concentration terms on which the rate of reaction depends when
determined experimentally.
 It’s a experimental value, a whole number or a fraction.
 For a reaction, aA + bB cC + dD
Rate = K [𝐴]𝑥
] [𝐵]𝑦
Order = x + y

6.  Zero order reaction
 First order reaction
 Second order reaction
 Pseudo-zero order reaction
 Pseudo-first order reaction