Chemical Kinetics Class 12 Notes Free PDF Download

1. Chemical Kinetics Class 12 Notes Free PDF Study Chemical Kinetics Class 12 Notes given below and download in pdf. Our teacher has planned these revision notes to assist Class 12 Students before attending the board exam and if prepared properly, you can score higher marks in your board exam. You can access more chapter-wise Revision Notes for Class 12 Chemistry and furthermore get the most recent topic-wise study material according to the NCERT syllabus for any subject on studiestoday.com free of charge. Chemical kinetics- The branch of physical chemistry which deals with the study of rate of reaction and their mechanism is called chemical kinetics. Rate of chemical reaction- The change in concentration of any reactant or product per unit time is called rate of reaction. Its Unit is moll-1 sec-1 or atm sec-1 TYPES OF RATE OF REACTION- 1. Average rate of reaction- The rate of reaction measured over the long time interval is called average rate of reaction. R ——→ P Avg rate = -Δ[R]/Δt = +Δ[P]/Δt 2. Instantaneous rate of reaction- The rate of reaction measured at a particular time is called instantaneous rate of reaction. Instantaneous rate = -d[R]/dt=+d[P]/dt RATE OF REACTION FOR THE EQUATION WITH STOICHIOMETRIC COEFFCIENTS: aA+ bB —→ C + dD rate of reaction= -1d[A] = -1d[B] = 1d[C] = 1d [D] a dt bdt cdt d dt FACTORS AFFECTING RATE OF REACTION- 1. Concentration of reactant: rate of reaction is directly proportional to concentration of reactants. 2. Surface area: greater the surface area faster is the reaction. 3. Temperature: rate of reaction increases with temperature 4. Nature of reactant: rate of reaction is faster in ionic compounds than covalent compounds.

2. 5. Presence of catalyst: it increases the rate of reaction by lowering activation energy. 6. Radiation: rate of reaction increases with radiation in photochemical reactions RATE LAW- The rate of reaction is directly proportional to the product of concentration of reactant and each concentration is raised to some power which may or may not be equal to stereochemistry experimentally For a reaction aA+bB → cC+dD Rate law = k[A]p[B]q Where powers p and q are determined experimentally which may or may not be equal to stoichiometry coefficient. RATE CONSTANT (k)- It is equal to the rate of reaction when molecular concentration of reactant is at unity. Units of rate constant for nth order : (molL-1) 1-n sec-1 or (atm or bar) 1-n sec-1 for gaseous reaction Units of k for zero order is moll-1 sec-1 Units of k for 1st order is sec-1 Units of k for 2nd order is mol2l-2 sec-1 MOLECULARITY – The total no. of reactants taking part in elementary chemical reaction is called molecularity. ORDER OF REACTION- The sum of powers to which the concentrations terms are raised in a rate law expression is called order of reactions. For above case order = p+q: orders of rn is determined experimentally. Zero order reaction: rate of reaction does not depend upon concentration of reactants. For eg decomposition of ammonia 2NH3 —→ N2+ 3H2 rate = k[R]0 First order reaction: decomposition of sulphuryl chloride SO2Cl2 —→ SO2+ Cl2 rate = k[R]

3. Second order reaction: for eg decomposition of HI 2HI —→ H2+ I2 rate = k[R]2 Third order reaction: for eg 2NO+ O2 —→ 2NO2 METHODS TO CALCULATE ORDER OF REACTION: 1. Graphical method 2. Initial rate method 3. Integrated rate method 4. Half-life method. Integrated rate equation: Zero order reaction: k=[R0]-[R] /t first order reaction: k= 2.303/t log [R0]/ [R] HALF-LIFE PERIOD- The time during which the concentration of the reactant is reduced to half of its initial concentration is called half-life period. For zero order, t1/2 = [R0]/2k For 1st order , t1/2 = 0.693/k Pseudofirst order reaction: It is reaction which seems to be higher order but actually of first order. For example: hydrolysis of ester ACTIVATION ENERGY- The minimum amount of energy absorbed by reactant molecules so that their energy becomes equal to the threshold energy is called activation energy. Activation energy = Threshold energy – kinetic energy Temperature dependence on rate of reaction: rate of reaction becomes almost double when temperature increases to 10k Temperature coefficient- The ratio of rate constant at two temperatures having difference of 100C is called temperature coefficient. Temperature coefficient = Rate constant at T+100C/Rate constant at T0C Arrhenius Equation- k= Ae-Ea/RT

4. k-rate constant ,A-Arrhenius factor, Ea-Activation energy, R- Rate constant T-Temperature Log k = Log A- Ea/2.303RT Energy of activation can be evaluated as log k2 = Ea k1 2.303R T1 T2 ( 1- 1 ) COLLISION THEORY 1. For a reaction to occur the collisions should be effective.( collisions which lead to formation of products are called effective collisions.) 2. For effective collisions molecules must overcome energy barrier and orientation barrier. Please click the link below to download pdf file for CBSE Class 12 Chemistry Revision Chemical Kinetics. Click to view or Download Pdf file We hope this Chemical Kinetics Class 12 Notes help you to make preparations better. For any inquiries relating to Chemical Kinetics Class 12 Notes, don't hesitate and leave questions in the comment box.