ChemistryNCERT Class 12

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Chemical Kinetics Notes

Study Notes

5 Topics27 Formulas44 PYQs36 Key Points

Chapter Overview Rate of Reaction Factors Affecting Rate Order & Molecularity Integrated Rate Equations Arrhenius Equation & Collision Theory

Chapter at a Glance

Topics5

Key Points36

Formulas27

Diagrams19

NEET PYQs44

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Topics

Chapter Overview

Overview

Chemical Kinetics studies how fast chemical reactions occur and why their speeds change under different conditions. In NCERT and NEET, the chapter revolves around rate of reaction, rate law, order, molecularity, integrated rate equations, half-life, Arrhenius equation, activation energy and collision theory. Thermodynamics tells whether a reaction is possible, but kinetics tells how quickly it reaches completion. A reaction may be thermodynamically feasible but kinetically slow, like conversion of diamond to graphite. This chapter is highly numerical and graph-based. NEET commonly asks units of rate constant, graphical identification of order, half-life dependence, pseudo first order reactions and activation energy from Arrhenius plots.

Key Points6

1The chapter has two major numerical areas: integrated rate laws and Arrhenius equation.
2Graph slopes are very important: zero order [R] vs t has slope -k, first order log[R] vs t has slope -k/2.303, and Arrhenius plot log k vs 1/T has slope -Ea/2.303R.
3Order may be zero, fractional, integral or negative; molecularity is always a positive integer.
4Rate constant k is independent of concentration but strongly depends on temperature and catalyst.
5Half-life trends are powerful shortcuts for identifying order.
6Collision theory explains that only properly oriented collisions with energy greater than threshold energy are effective.

Memory Tricks2

Kinetics Keyword

Remember: Kinetics = K for 'Kaise fast?' It answers how fast a reaction occurs, not whether it is possible.

Graph Shortcut

Straight line graph reveals order: [R] vs t means zero order, log[R] vs t means first order, 1/[R] vs t means second order.

Examples2

Rusting of Iron

Rusting is thermodynamically possible but slow. Moisture, oxygen and surface conditions affect its rate.

Food Spoilage

Food spoils slower in a refrigerator because lower temperature decreases rate constants of biochemical reactions.

Reference Tables2

Formula Sheet for Chemical Kinetics

Concept	Formula	NEET Use
Rate law	r = k[A]^x[B]^y	Find order and k
Zero order integrated law	[R] = [R]0 - kt	Linear [R] vs t graph
First order integrated law	k = 2.303/t log([R]0/[R])	Most common NEET numerical
Second order law	1/[R] - 1/[R]0 = kt	Identify from 1/[R] vs t graph
Arrhenius two-temperature form	log(k2/k1) = Ea/2.303R × (T2 - T1)/(T1T2)	Find Ea or changed rate constant

Mind Map of the Chapter

Branch	Main Idea	Core Output
Rate	How fast reaction occurs	Average and instantaneous rate
Factors	What changes reaction speed	Concentration, temperature, catalyst, surface area
Order and molecularity	How rate depends on reactants	Rate law and mechanism clues
Integrated equations	Concentration-time relation	Graphs and half-life
Arrhenius and collision theory	Why temperature affects rate	Activation energy and effective collisions

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Common Mistakes2

Confusing Thermodynamics and Kinetics

A negative ΔG means a reaction is feasible, but it may still be extremely slow without a suitable pathway.

Assuming Balanced Equation Gives Rate Law

For complex reactions, rate law must be determined experimentally; stoichiometric coefficients are not automatically orders.

Formula Cards4

General Rate of Reaction

Measures concentration change per unit time. Negative sign is used for reactant disappearance, positive sign for product formation.

Variables

Δ[Reactant]=

Change in concentration of reactant

Δ[Product]=

Change in concentration of product

Δt=

Time interval

Rate Law

Experimental relationship between reaction rate and molar concentrations of reactants.

Variables

k=

Rate constant

x, y=

Orders with respect to A and B

x + y=

Overall order of reaction

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Diagrams3

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Rate of Reaction

Overview

Rate of reaction tells how quickly reactants are consumed or products are formed. For a reaction, it is expressed as change in concentration per unit time and usually has unit mol L⁻¹ s⁻¹. Average rate is calculated over a finite time interval, while instantaneous rate is the slope of tangent to concentration-time curve at a particular moment. Rate expression must consider stoichiometric coefficients so that the same reaction rate is obtained from any reactant or product. Rate law expresses rate in terms of molar concentrations raised to experimentally determined powers. NEET often tests signs, units, stoichiometric division, rate law interpretation and numerical substitution.

Key Points6

1For aA + bB → cC + dD, rate = -1/a d[A]/dt = -1/b d[B]/dt = 1/c d[C]/dt = 1/d d[D]/dt.
2Instantaneous rate is more accurate for changing rates and is obtained graphically from tangent slope.
3Rate law is not the same as balanced chemical equation for complex reactions.
4The rate constant k equals rate when all concentration terms are unity.
5The units of k change with overall order, but unit of rate remains concentration per time.
6Reaction rate generally decreases with time as reactant concentration decreases.

Memory Tricks2

Reactant Negative, Product Positive

Reactants go down, so put minus sign; products go up, so put plus sign.

Rate Law is Experimental

Remember 'LAW is from LAB': rate law comes from experiment, not from just looking at the balanced equation.

Examples2

Solved Numerical: Average Rate

If [A] decreases from 0.50 M to 0.30 M in 20 s, average rate of disappearance of A = -(0.30 - 0.50)/20 = 0.010 mol L⁻¹ s⁻¹.

PYQ Concept: Rate Expression

For 2A + B → 3C, if d[C]/dt = 0.06 M s⁻¹, reaction rate = 1/3 × 0.06 = 0.02 M s⁻¹ and rate of disappearance of A = 2 × 0.02 = 0.04 M s⁻¹.

Reference Tables2

Rate Terms and Meaning

Term	Meaning	Graphical Idea
Average rate	Rate over a time interval	Slope of chord
Instantaneous rate	Rate at one instant	Slope of tangent
Rate of disappearance	Reactant concentration decreases	Negative concentration slope
Rate of formation	Product concentration increases	Positive concentration slope

Units of Rate and Rate Constant

Overall Order	Rate Law Form	Unit of k
Zero	r = k	mol L⁻¹ s⁻¹
First	r = k[A]	s⁻¹
Second	r = k[A]² or k[A][B]	L mol⁻¹ s⁻¹
n	r = k(concentration)^n	(mol L⁻¹)^(1-n) s⁻¹

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Common Mistakes3

Forgetting Stoichiometric Division

For 2N2O5 → 4NO2 + O2, the reaction rate is -1/2 d[N2O5]/dt, not simply -d[N2O5]/dt.

Wrong Unit of Rate

Rate unit remains mol L⁻¹ s⁻¹ even if the reaction order changes; only the unit of k changes.

Using Product Coefficient as Order

Order is not obtained from product coefficients. It is obtained from the rate law.

Formula Cards4

Average Rate

Used when concentration change is measured over a finite time interval.

Variables

Δ[R]=

Change in reactant concentration

Δ[P]=

Change in product concentration

Δt=

Time interval

Instantaneous Rate

Rate at a particular instant; equal to slope of tangent on concentration-time graph.

Variables

d[R]=

Infinitesimal change in reactant concentration

dt=

Infinitesimal time interval

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Factors Affecting Rate

Overview

Reaction rate changes because the number and effectiveness of molecular collisions change. Ionic reactions in aqueous solution are often very fast, while covalent bond-breaking reactions may be slower because old bonds must break and new bonds must form. Increasing concentration or pressure usually increases collision frequency. Raising temperature increases kinetic energy and greatly increases the fraction of molecules crossing activation energy. A catalyst provides an alternate pathway with lower activation energy and speeds both forward and reverse reactions. Greater surface area allows more particles to be exposed for reaction. NEET frequently asks qualitative effects, catalyst misconceptions, temperature coefficient and graphical observations.

Key Points6

1Rate increases when effective collision frequency increases.
2Temperature affects both kinetic energy and Arrhenius factor e^(-Ea/RT).
3A catalyst does not change ΔG, ΔH or equilibrium constant; it only helps reach equilibrium faster.
4Surface area matters mainly for heterogeneous reactions involving solids.
5Pressure affects rate mainly for gaseous reactions.
6The same factor may affect different reactions differently depending on rate law.

Memory Tricks2

FACTS Control Rate

F-A-C-T-S: Frequency of collisions, Activation energy, Concentration, Temperature, Surface area.

Catalyst Shortcut

Catalyst = 'Cut Ea'. It cuts activation energy by providing a new pathway.

Examples3

Experimental Observation: Marble and HCl

Powdered CaCO3 reacts faster with dilute HCl than marble chips because more CaCO3 surface is exposed to acid.

Real Life: Refrigerator

Low temperature slows bacterial and enzymatic reactions, so food lasts longer in a refrigerator.

PYQ Concept: Pressure

Increasing pressure increases rate significantly for gaseous reactants but not directly for reactions in dilute liquid solutions.

Reference Tables2

Factors Affecting Rate

Factor	Effect on Rate	Reason
Nature of reactants	Ionic often faster than covalent	Less bond rearrangement in many ionic reactions
Concentration	Usually increases rate	More collisions per unit volume
Temperature	Strongly increases rate	More molecules cross activation energy
Pressure	Increases rate for gases	Increases gaseous concentration
Catalyst	Increases rate	Lowers activation energy
Surface area	Increases rate for solids	More exposed reactive sites

Catalyst vs Temperature

Feature	Catalyst	Temperature Increase
Activation energy	Decreases by alternate path	Does not decrease Ea
Fraction of effective molecules	Increases	Increases
Equilibrium constant	No change	May change if temperature changes
Consumption	Regenerated	Not applicable

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Common Mistakes3

Thinking Catalyst Changes Equilibrium

Catalyst speeds up attainment of equilibrium but does not change equilibrium constant or final equilibrium composition.

Saying Temperature Lowers Ea

Temperature increases molecular energy; it does not lower activation energy. Catalyst lowers activation energy.

Ignoring Surface Area

A solid lump and same mass of powder can react at very different rates due to exposed area.

Formula Cards3

Concentration Dependence

Changing concentration changes rate according to reaction orders.

Variables

x=

Order with respect to A

y=

Order with respect to B

k=

Rate constant at fixed temperature

Temperature Dependence

Rate constant increases when temperature increases because the exponential term increases.

Variables

Ea=

Activation energy

T=

Absolute temperature

A=

Frequency factor

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Order & Molecularity

Overview

Order and molecularity describe reaction dependence and mechanism, but they are not the same. Order is the sum of powers of concentration terms in the experimentally determined rate law. It may be zero, fractional, integral or even negative. Molecularity is the number of reacting species participating in one elementary step and is always a positive integer. Zero order reactions have rate independent of reactant concentration, first order reactions have rate proportional to one concentration term, and second order reactions have total concentration power two. Pseudo first order reactions are actually higher order but behave as first order because one reactant is in large excess, such as hydrolysis of ester in water.

Key Points6

1Overall order = sum of powers in rate law.
2Molecularity indicates how many species collide in an elementary event.
3Complex reactions occur through multiple elementary steps, and the slowest step often controls rate.
4A first order reaction has k unit s⁻¹.
5For zero order reactions, rate remains constant until reactant is nearly exhausted.
6Pseudo first order reactions simplify difficult kinetics and are common in solution chemistry.

Memory Tricks3

Order is from Rate Law

Order = 'Power in rate law'. Look at exponents, add them, and ignore product terms.

Molecularity Must be Countable

Molecularity counts molecules colliding, so it cannot be zero or fractional.

Pseudo Means Fake Appearance

Pseudo first order is not truly first order; it only appears first order because one reactant is in excess.

Examples3

Numerical Example: Finding Order

If rate law is r = k[A]^1[B]^2, order with respect to A is 1, with respect to B is 2, and overall order is 3.

Pseudo First Order Example

Acid hydrolysis of ethyl acetate: CH3COOC2H5 + H2O → CH3COOH + C2H5OH. Water is solvent and in large excess, so reaction behaves as first order with respect to ester.

PYQ Concept: Doubling Concentration

For r = k[A]^2, if [A] is doubled, new rate = k(2[A])^2 = 4k[A]^2, so rate becomes four times.

Reference Tables3

Order vs Molecularity

Feature	Order	Molecularity
Definition	Sum of powers in rate law	Number of species in elementary step
How determined	Experimentally	From mechanism elementary step
Possible values	Zero, fractional, integral, negative	Positive integers only
Applies to	Overall reaction	Elementary step
Can be zero?	Yes	No
Can be fractional?	Yes	No

Common Orders in NEET

Order	Rate Law	If Concentration Doubles
Zero	r = k	Rate unchanged
First	r = k[A]	Rate doubles
Second	r = k[A]^2	Rate becomes four times
Second	r = k[A][B]	If both double, rate becomes four times

Examples of Molecularity

Elementary Step	Molecularity	Name
A → Products	1	Unimolecular
A + B → Products	2	Bimolecular
2A + B → Products	3	Termolecular, rare

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Common Mistakes3

Taking Stoichiometric Coefficient as Order

For complex reactions, coefficients are not equal to order unless experimentally proven.

Using Molecularity for Overall Complex Reaction

Molecularity is meaningful for elementary steps, not for an overall complex reaction.

Calling Molecularity Zero

Zero molecularity is impossible because no reaction can occur without reacting species.

Formula Cards5

Overall Order

The total order is the sum of powers of concentration terms in the rate law.

Variables

x=

Order with respect to reactant A

y=

Order with respect to reactant B

Zero Order Rate Law

Rate is independent of reactant concentration.

Variables

r=

Rate of reaction

k=

Zero order rate constant

First Order Rate Law

Rate is directly proportional to concentration of one reactant.

Variables

[A]=

Molar concentration of reactant A

k=

First order rate constant

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Integrated Rate Equations

10m

Overview

Integrated rate equations connect reactant concentration with time and allow calculation of rate constant, remaining concentration and half-life. They are essential because experimental concentration-time data is easier to measure than instantaneous rate. For zero order reactions, concentration falls linearly with time and half-life is directly proportional to initial concentration. For first order reactions, logarithmic concentration changes linearly with time and half-life is constant. For second order reactions, reciprocal concentration varies linearly with time and half-life is inversely proportional to initial concentration. NEET repeatedly asks identification of order from straight-line graph, slope formulas, half-life patterns and first order numerical calculations using log values.

Key Points6

1Integrated rate laws are used when concentration changes continuously with time.
2For first order reactions, equal time intervals reduce concentration by the same fraction.
3In first order decay, after n half-lives, remaining amount = initial amount/2^n.
4Graphical representation is a quick way to identify reaction order.
5Units of k confirm order: zero order M s⁻¹, first order s⁻¹, second order M⁻¹ s⁻¹.
6Most radioactive decay and many decomposition reactions follow first order kinetics.

Memory Tricks3

Graph Order Trick

Zero: [R] straight. First: log[R] straight. Second: 1/[R] straight.

First Order Half-Life

First order half-life is 'free from initial concentration': t1/2 = 0.693/k.

Slope Signs

Reactant concentration graphs go down for zero and first order, so slopes are negative. Reciprocal concentration graph goes up for second order, so slope is positive.

Examples3

Solved Numerical: First Order k

A first order reaction is 75% complete in 20 min. Remaining = 25% = 1/4. k = 2.303/20 log(100/25) = 2.303/20 log4 = 2.303/20 × 0.602 = 0.0693 min⁻¹.

Solved Numerical: Half-Life

If k = 0.0231 s⁻¹ for a first order reaction, t1/2 = 0.693/0.0231 = 30 s.

PYQ Concept: Graph Identification

If a plot of 1/[A] vs time is straight line, the reaction is second order with respect to A.

Reference Tables3

Integrated Rate Equations Comparison

Order	Integrated Equation	Straight Line Graph	Slope
Zero	[R] = [R]0 - kt	[R] vs t	-k
First	log[R] = log[R]0 - kt/2.303	log[R] vs t	-k/2.303
Second	1/[R] = 1/[R]0 + kt	1/[R] vs t	k

Half-Life Dependence

Order	Half-Life Formula	Dependence on Initial Concentration
Zero	t1/2 = [R]0/2k	Directly proportional
First	t1/2 = 0.693/k	Independent
Second	t1/2 = 1/k[R]0	Inversely proportional

Shortcut Methods for NEET

Situation	Shortcut	Use
First order, 50% left	t = t1/2	One half-life
First order, 25% left	t = 2t1/2	Two half-lives
First order, 12.5% left	t = 3t1/2	Three half-lives
Graph has [R] vs t straight line	Zero order	Slope gives -k
Graph has log[R] vs t straight line	First order	Slope gives -k/2.303

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Common Mistakes3

Using Natural Log and Common Log Wrongly

ln([R]0/[R]) = kt, but log([R]0/[R]) needs factor 2.303: k = 2.303/t log([R]0/[R]).

Assuming All Half-Lives are Constant

Only first order half-life is independent of initial concentration. Zero and second order half-lives depend on [R]0.

Wrong Slope for First Order Graph

For log[R] vs t, slope = -k/2.303, so k = -2.303 × slope.

Formula Cards6

Zero Order Integrated Rate Law

Reactant concentration decreases linearly with time.

Variables

[R]=

Concentration at time t

[R]0=

Initial concentration

k=

Zero order rate constant

t=

Time

Zero Order Half-Life

Half-life is directly proportional to initial concentration.

Variables

t1/2=

Half-life period

[R]0=

Initial reactant concentration

k=

Zero order rate constant

First Order Integrated Rate Law

Most important NEET formula for first order reactions.

Variables

k=

First order rate constant

[R]0=

Initial concentration

[R]=

Remaining concentration at time t

t=

Time

First Order Half-Life

Half-life is independent of initial concentration.

Variables

t1/2=

Time for concentration to reduce to half

k=

First order rate constant

Second Order Integrated Rate Law

For a second order reaction involving one reactant, reciprocal concentration increases linearly with time.

Variables

[R]=

Concentration at time t

[R]0=

Initial concentration

k=

Second order rate constant

Second Order Half-Life

Half-life decreases when initial concentration increases.

Variables

t1/2=

Half-life period

k=

Second order rate constant

[R]0=

Initial concentration

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Arrhenius Equation & Collision Theory

Overview

Arrhenius equation explains the strong dependence of rate constant on temperature and activation energy. Molecules must acquire minimum energy to form an activated complex or transition state before converting into products. This minimum extra energy is activation energy. A small rise in temperature can cause a large increase in rate because many more molecules cross the activation energy barrier. Collision theory adds that not every collision gives product; collisions must have sufficient energy and proper orientation. The Arrhenius plot of log k versus 1/T is a straight line whose slope gives activation energy. NEET commonly asks activation energy calculation, catalyst effect and effective collision concepts.

Key Points6

1Threshold energy is the minimum total energy needed for reaction.
2Activation energy = threshold energy - average energy of reactants.
3Only a fraction of collisions are effective.
4Frequency factor A represents collision frequency and orientation-related factors.
5Catalyst changes the reaction pathway, not the initial or final energy of reactants and products.
6For exothermic reactions, Ea for forward and backward reactions differ by enthalpy change.

Memory Tricks3

Arrhenius Plot Slope

log k vs 1/T always slopes down because increasing 1/T means decreasing temperature, so k decreases.

Effective Collision

Collision must have 'E plus O': Enough energy plus proper Orientation.

Catalyst Rule

Catalyst changes the road, not the start or finish. It lowers the hill but reactant and product energies remain same.

Examples4

Solved Numerical: Activation Energy from Slope

If slope of log k vs 1/T plot is -5000 K, then slope = -Ea/2.303R. Ea = 5000 × 2.303 × 8.314 = 95720 J mol⁻¹ ≈ 95.7 kJ mol⁻¹.

Solved Numerical: Temperature Effect

If k2/k1 = 2 for a 10 K rise, the reaction rate approximately doubles. This is a common temperature coefficient idea.

Real Life: Enzymes

Enzymes are biological catalysts. They increase reaction rate by lowering activation energy through a suitable active site orientation.

PYQ Concept: Catalyst and Equilibrium

A catalyst increases both forward and reverse rates, so equilibrium is reached faster but equilibrium constant remains unchanged.

Reference Tables3

Arrhenius Terms

Term	Meaning	Effect on Rate
Ea	Activation energy barrier	Higher Ea means lower rate
A	Frequency factor	Higher A generally increases rate
T	Absolute temperature	Higher T increases rate constant
e^(-Ea/RT)	Energy factor	Fraction of molecules able to react
P	Orientation factor	Correct orientation increases effective collisions

Collision Types

Collision Type	Energy Condition	Orientation	Result
Ineffective due to low energy	Energy < Ea	May be correct	No product
Ineffective due to wrong orientation	Energy ≥ Ea	Wrong	No product
Effective collision	Energy ≥ Ea	Correct	Product formed

Catalysed vs Uncatalysed Reaction

Feature	Uncatalysed	Catalysed
Pathway	Original path	Alternate path
Activation energy	Higher	Lower
Rate	Slower	Faster
ΔH	Same	Same
Equilibrium constant	Same	Same

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Common Mistakes4

Using Celsius in Arrhenius Equation

Always use kelvin for T in Arrhenius calculations.

Wrong Sign in Two-Temperature Formula

If T2 > T1, k2 should usually be greater than k1. Check that log(k2/k1) is positive.

Saying Every Collision is Effective

Only collisions with energy greater than or equal to Ea and correct orientation lead to products.

Thinking Catalyst is Used Up

A catalyst participates in the mechanism but is regenerated at the end.

Formula Cards5

Arrhenius Equation

Relates rate constant to activation energy and temperature.

Variables

k=

Rate constant

A=

Frequency factor

Ea=

Activation energy

R=

Gas constant, 8.314 J mol⁻¹ K⁻¹

T=

Absolute temperature

Logarithmic Arrhenius Equation

Used for Arrhenius plot and activation energy from slope.

Variables

log k=

Common logarithm of rate constant

log A=

Intercept of Arrhenius plot

Ea/(2.303R)=

Magnitude related to slope

Two-Temperature Arrhenius Equation

Used to calculate activation energy or rate constant at another temperature.

Variables

k1, k2=

Rate constants at temperatures T1 and T2

T1, T2=

Absolute temperatures in kelvin

Ea=

Activation energy

Activation Energy Relation

Activation energy is the extra energy needed to reach activated complex.

Variables

Ea=

Activation energy

Threshold energy=

Minimum energy required for effective reaction

Collision Theory Rate Constant

For collision theory, rate depends on steric factor, collision frequency and energy factor.

Variables

P=

Steric factor or orientation factor

Z=

Collision frequency

e^(-Ea/RT)=

Fraction of molecules with sufficient energy

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Formula Sheet

General Rate of Reaction

Measures concentration change per unit time. Negative sign is used for reactant disappearance, positive sign for product formation.

Variables

Δ[Reactant]=

Change in concentration of reactant

Δ[Product]=

Change in concentration of product

Δt=

Time interval

Rate Law

Experimental relationship between reaction rate and molar concentrations of reactants.

Variables

k=

Rate constant

x, y=

Orders with respect to A and B

x + y=

Overall order of reaction

First Order Half-Life

For first order reaction, half-life remains constant and does not depend on initial concentration.

Variables

t1/2=

Time required for concentration to become half

k=

First order rate constant

Arrhenius Equation

Shows how rate constant changes with temperature and activation energy.

Variables

A=

Frequency factor

Ea=

Activation energy

R=

Gas constant

T=

Absolute temperature in kelvin

Average Rate

Used when concentration change is measured over a finite time interval.

Variables

Δ[R]=

Change in reactant concentration

Δ[P]=

Change in product concentration

Δt=

Time interval

Instantaneous Rate

Rate at a particular instant; equal to slope of tangent on concentration-time graph.

Variables

d[R]=

Infinitesimal change in reactant concentration

dt=

Infinitesimal time interval

Stoichiometric Rate Expression

For aA + bB → cC + dD, division by coefficients gives a single reaction rate.

Variables

a, b, c, d=

Stoichiometric coefficients

A, B=

Reactants

C, D=

Products

Rate Law

Relates rate to concentration of reactants with experimentally determined powers.

Variables

r=

Reaction rate

k=

Rate constant

x, y=

Partial orders with respect to A and B

Concentration Dependence

Changing concentration changes rate according to reaction orders.

Variables

x=

Order with respect to A

y=

Order with respect to B

k=

Rate constant at fixed temperature

Temperature Dependence

Rate constant increases when temperature increases because the exponential term increases.

Variables

Ea=

Activation energy

T=

Absolute temperature

A=

Frequency factor

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Rate of reaction is change in concentration of reactant or product per unit time.

Rate law is experimentally determined and cannot be predicted from balanced equation except for elementary reactions.

Order is the sum of powers of concentration terms in the rate law.

Molecularity is the number of reacting species involved in an elementary step.

For first order reactions, t1/2 = 0.693/k and is independent of initial concentration.

Arrhenius equation is k = A e^(-Ea/RT).

A catalyst increases rate by lowering activation energy, not by changing equilibrium constant.

Chemical kinetics links experiments, graphs and numerical formulas.

The chapter has two major numerical areas: integrated rate laws and Arrhenius equation.

Graph slopes are very important: zero order [R] vs t has slope -k, first order log[R] vs t has slope -k/2.303, and Arrhenius plot log k vs 1/T has slope -Ea/2.303R.

Rate = change in concentration/change in time.

For reactants, rate of disappearance is written with a negative sign.

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NEET PYQs — Chemical Kinetics

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NEET 2026Set 11MediumQ1

Given the expression for the rate constant of a first-order reaction at temperature T(K): ln k = 14.34 − (1.25 × 10⁴)/T. The energy of activation in kcal mol⁻¹ is: (Given: k in s⁻¹, R = 1.987 cal mol⁻¹ K⁻¹)