This document provides an overview of chemical kinetics and reaction rates. It discusses:
1) Chemical kinetics deals with how fast chemical reactions occur and the factors that affect reaction rates.
2) Reaction rates can vary significantly, from fractions of a second to years, as seen in examples of iron rusting and silver chloride formation.
3) The study of chemical kinetics involves determining rates of reaction, factors affecting rates, and reaction mechanisms.
It then provides examples and methods for determining reaction order and the effect of temperature on reaction rates.
The branch of chemistry, which deals with the study of reaction rates and their mechanisms, called chemical kinetics.
Thermodynamics tells only about the feasibility of a reaction whereas chemical kinetics tells about the rate of a reaction.
For example, thermodynamic data indicate that diamond shall convert to graphite but in reality the conversion rate is so slow that the change is not perceptible at all.
This presentation consists of three topics that are:
1. conductance of electrolytic solution
2. Specific Conductance, Molar Conductance & Equivalent Conductance
3. Kohlrausch's Law
The branch of chemistry, which deals with the study of reaction rates and their mechanisms, called chemical kinetics.
Thermodynamics tells only about the feasibility of a reaction whereas chemical kinetics tells about the rate of a reaction.
For example, thermodynamic data indicate that diamond shall convert to graphite but in reality the conversion rate is so slow that the change is not perceptible at all.
This presentation consists of three topics that are:
1. conductance of electrolytic solution
2. Specific Conductance, Molar Conductance & Equivalent Conductance
3. Kohlrausch's Law
Definition - Mechanism - Effect of dielectric constant on the rate of reactions in solutions - Salt effect - Primary salt effect - Bronsted – Bjerrum equation - Secondary salt effect - Effect of pressure on rate of reaction in solution - Volume of activation - Significance
lecture slide on:
Gibbs free energy and Nernst Equation, Faradaic Processes and Factors Affecting Rates of Electrode Reactions, Potentials and Thermodynamics of Cells, Kinetics of Electrode Reactions, Kinetic controlled reactions,Essentials of Electrode Reactions,BUTLER-VOLMER MODEL FOR THE ONE-STEP, ONE-ELECTRON PROCESS,Current-overpotential curves for the system, Mass Transfer by Migration And Diffusion,MASS-TRANSFER-CONTROLLED REACTIONS,
1. What is the steady state approximation
2.Definition of Steady state approximation
3. In Chemical kinetics in steady state state approximation
4. Mechanism involving in steady state approximation
5. rate of formation, using steady state approximation plot
1)order of reactions
2)second order of reaction
3)units of 2nd order reaction
4) rate equation of second order reaction
5) 2nd order reaction with different initial concentration and equal concentration of reactant
Definition - Mechanism - Effect of dielectric constant on the rate of reactions in solutions - Salt effect - Primary salt effect - Bronsted – Bjerrum equation - Secondary salt effect - Effect of pressure on rate of reaction in solution - Volume of activation - Significance
lecture slide on:
Gibbs free energy and Nernst Equation, Faradaic Processes and Factors Affecting Rates of Electrode Reactions, Potentials and Thermodynamics of Cells, Kinetics of Electrode Reactions, Kinetic controlled reactions,Essentials of Electrode Reactions,BUTLER-VOLMER MODEL FOR THE ONE-STEP, ONE-ELECTRON PROCESS,Current-overpotential curves for the system, Mass Transfer by Migration And Diffusion,MASS-TRANSFER-CONTROLLED REACTIONS,
1. What is the steady state approximation
2.Definition of Steady state approximation
3. In Chemical kinetics in steady state state approximation
4. Mechanism involving in steady state approximation
5. rate of formation, using steady state approximation plot
1)order of reactions
2)second order of reaction
3)units of 2nd order reaction
4) rate equation of second order reaction
5) 2nd order reaction with different initial concentration and equal concentration of reactant
Multi-source connectivity as the driver of solar wind variability in the heli...Sérgio Sacani
The ambient solar wind that flls the heliosphere originates from multiple
sources in the solar corona and is highly structured. It is often described
as high-speed, relatively homogeneous, plasma streams from coronal
holes and slow-speed, highly variable, streams whose source regions are
under debate. A key goal of ESA/NASA’s Solar Orbiter mission is to identify
solar wind sources and understand what drives the complexity seen in the
heliosphere. By combining magnetic feld modelling and spectroscopic
techniques with high-resolution observations and measurements, we show
that the solar wind variability detected in situ by Solar Orbiter in March
2022 is driven by spatio-temporal changes in the magnetic connectivity to
multiple sources in the solar atmosphere. The magnetic feld footpoints
connected to the spacecraft moved from the boundaries of a coronal hole
to one active region (12961) and then across to another region (12957). This
is refected in the in situ measurements, which show the transition from fast
to highly Alfvénic then to slow solar wind that is disrupted by the arrival of
a coronal mass ejection. Our results describe solar wind variability at 0.5 au
but are applicable to near-Earth observatories.
This presentation explores a brief idea about the structural and functional attributes of nucleotides, the structure and function of genetic materials along with the impact of UV rays and pH upon them.
Professional air quality monitoring systems provide immediate, on-site data for analysis, compliance, and decision-making.
Monitor common gases, weather parameters, particulates.
Seminar of U.V. Spectroscopy by SAMIR PANDASAMIR PANDA
Spectroscopy is a branch of science dealing the study of interaction of electromagnetic radiation with matter.
Ultraviolet-visible spectroscopy refers to absorption spectroscopy or reflect spectroscopy in the UV-VIS spectral region.
Ultraviolet-visible spectroscopy is an analytical method that can measure the amount of light received by the analyte.
This pdf is about the Schizophrenia.
For more details visit on YouTube; @SELF-EXPLANATORY;
https://www.youtube.com/channel/UCAiarMZDNhe1A3Rnpr_WkzA/videos
Thanks...!
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
Deep Behavioral Phenotyping in Systems Neuroscience for Functional Atlasing a...Ana Luísa Pinho
Functional Magnetic Resonance Imaging (fMRI) provides means to characterize brain activations in response to behavior. However, cognitive neuroscience has been limited to group-level effects referring to the performance of specific tasks. To obtain the functional profile of elementary cognitive mechanisms, the combination of brain responses to many tasks is required. Yet, to date, both structural atlases and parcellation-based activations do not fully account for cognitive function and still present several limitations. Further, they do not adapt overall to individual characteristics. In this talk, I will give an account of deep-behavioral phenotyping strategies, namely data-driven methods in large task-fMRI datasets, to optimize functional brain-data collection and improve inference of effects-of-interest related to mental processes. Key to this approach is the employment of fast multi-functional paradigms rich on features that can be well parametrized and, consequently, facilitate the creation of psycho-physiological constructs to be modelled with imaging data. Particular emphasis will be given to music stimuli when studying high-order cognitive mechanisms, due to their ecological nature and quality to enable complex behavior compounded by discrete entities. I will also discuss how deep-behavioral phenotyping and individualized models applied to neuroimaging data can better account for the subject-specific organization of domain-general cognitive systems in the human brain. Finally, the accumulation of functional brain signatures brings the possibility to clarify relationships among tasks and create a univocal link between brain systems and mental functions through: (1) the development of ontologies proposing an organization of cognitive processes; and (2) brain-network taxonomies describing functional specialization. To this end, tools to improve commensurability in cognitive science are necessary, such as public repositories, ontology-based platforms and automated meta-analysis tools. I will thus discuss some brain-atlasing resources currently under development, and their applicability in cognitive as well as clinical neuroscience.
Introduction:
RNA interference (RNAi) or Post-Transcriptional Gene Silencing (PTGS) is an important biological process for modulating eukaryotic gene expression.
It is highly conserved process of posttranscriptional gene silencing by which double stranded RNA (dsRNA) causes sequence-specific degradation of mRNA sequences.
dsRNA-induced gene silencing (RNAi) is reported in a wide range of eukaryotes ranging from worms, insects, mammals and plants.
This process mediates resistance to both endogenous parasitic and exogenous pathogenic nucleic acids, and regulates the expression of protein-coding genes.
What are small ncRNAs?
micro RNA (miRNA)
short interfering RNA (siRNA)
Properties of small non-coding RNA:
Involved in silencing mRNA transcripts.
Called “small” because they are usually only about 21-24 nucleotides long.
Synthesized by first cutting up longer precursor sequences (like the 61nt one that Lee discovered).
Silence an mRNA by base pairing with some sequence on the mRNA.
Discovery of siRNA?
The first small RNA:
In 1993 Rosalind Lee (Victor Ambros lab) was studying a non- coding gene in C. elegans, lin-4, that was involved in silencing of another gene, lin-14, at the appropriate time in the
development of the worm C. elegans.
Two small transcripts of lin-4 (22nt and 61nt) were found to be complementary to a sequence in the 3' UTR of lin-14.
Because lin-4 encoded no protein, she deduced that it must be these transcripts that are causing the silencing by RNA-RNA interactions.
Types of RNAi ( non coding RNA)
MiRNA
Length (23-25 nt)
Trans acting
Binds with target MRNA in mismatch
Translation inhibition
Si RNA
Length 21 nt.
Cis acting
Bind with target Mrna in perfect complementary sequence
Piwi-RNA
Length ; 25 to 36 nt.
Expressed in Germ Cells
Regulates trnasposomes activity
MECHANISM OF RNAI:
First the double-stranded RNA teams up with a protein complex named Dicer, which cuts the long RNA into short pieces.
Then another protein complex called RISC (RNA-induced silencing complex) discards one of the two RNA strands.
The RISC-docked, single-stranded RNA then pairs with the homologous mRNA and destroys it.
THE RISC COMPLEX:
RISC is large(>500kD) RNA multi- protein Binding complex which triggers MRNA degradation in response to MRNA
Unwinding of double stranded Si RNA by ATP independent Helicase
Active component of RISC is Ago proteins( ENDONUCLEASE) which cleave target MRNA.
DICER: endonuclease (RNase Family III)
Argonaute: Central Component of the RNA-Induced Silencing Complex (RISC)
One strand of the dsRNA produced by Dicer is retained in the RISC complex in association with Argonaute
ARGONAUTE PROTEIN :
1.PAZ(PIWI/Argonaute/ Zwille)- Recognition of target MRNA
2.PIWI (p-element induced wimpy Testis)- breaks Phosphodiester bond of mRNA.)RNAse H activity.
MiRNA:
The Double-stranded RNAs are naturally produced in eukaryotic cells during development, and they have a key role in regulating gene expression .
(May 29th, 2024) Advancements in Intravital Microscopy- Insights for Preclini...Scintica Instrumentation
Intravital microscopy (IVM) is a powerful tool utilized to study cellular behavior over time and space in vivo. Much of our understanding of cell biology has been accomplished using various in vitro and ex vivo methods; however, these studies do not necessarily reflect the natural dynamics of biological processes. Unlike traditional cell culture or fixed tissue imaging, IVM allows for the ultra-fast high-resolution imaging of cellular processes over time and space and were studied in its natural environment. Real-time visualization of biological processes in the context of an intact organism helps maintain physiological relevance and provide insights into the progression of disease, response to treatments or developmental processes.
In this webinar we give an overview of advanced applications of the IVM system in preclinical research. IVIM technology is a provider of all-in-one intravital microscopy systems and solutions optimized for in vivo imaging of live animal models at sub-micron resolution. The system’s unique features and user-friendly software enables researchers to probe fast dynamic biological processes such as immune cell tracking, cell-cell interaction as well as vascularization and tumor metastasis with exceptional detail. This webinar will also give an overview of IVM being utilized in drug development, offering a view into the intricate interaction between drugs/nanoparticles and tissues in vivo and allows for the evaluation of therapeutic intervention in a variety of tissues and organs. This interdisciplinary collaboration continues to drive the advancements of novel therapeutic strategies.
2. Introduction
Chemical kinetics deals with the rates
of chemical reactions . i.e., how fast a
chemical reaction occurs?
Such studies help to understand the
mechanism through which the reactants are
converted to product.
It is observed that some reactions occur
within a fraction of second, whereas some
reactions take years together for completion.
3. Consider the following chemical changes,
which occur at different speeds.
i) Rusting of iron:- It is a very slow reaction.
It may take days to months or years together
to undergo complete change.
ii) Digestion of food:- It is a reaction with
medium speed.
Usually the food is digested in 3-4 hours time.
iii)The formation of a white precipitate of silver
chloride, AgCl :-
When AgNO3 is added into aqueous solution
of chloride ions, (Cl–) precipitate of AgCl occurs in
a fraction of second. It is a very fast reaction.
4. The study of chemical kinetics deals with
the qualitative and quantitative study of:
a) The rates of reaction.
b) The factors affecting rate of reaction.
c) The mechanisms of reactions.
It also explains why some of the
thermodynamically feasible reactions occur
slowly; or do not occur unless initiated by
applying suitable conditions.
For example, burning of wood is a
spontaneous or feasible process according to
thermodynamic laws. But wood cannot burn
itself. It starts burning only after igniting it.
5. * Third Order Reactions:-
The reaction in which three molecules
are take part in reaction is called Third
Order Reaction.
Hence, Third Order Reactions are
also called termolecular reactions.
Eg.
1) 3A ⟶ product.
2) 2A + B ⟶ product.
3) A + B + C ⟶ product.
6. Derivation of rate constant :-
Let us consider a simple third order reaction
having equal concentration of all reactants.
3A ⟶ product.
Let, a = initial concentration of reactant ‘A’.
x = concentration of reactant ‘A’ at time ‘t’.
(a–x) = concentration of reactant ‘A’ after time ‘t’.
Then rate law is written as
… (1) K = 3rd order constant.
Rearranging eq.(1) we get,
7. ……….. (2)
Integrating eq.(2)
….. (3) C= constant
At t = 0 , x= 0 & we get,
Put value of C in eq.(3)
dx
(a−x)3 = k. 𝐝𝐭
𝟏
𝟐(a−x)2
= 𝐤𝐭 + 𝐂
C=
𝟏
𝟐a2
𝟏
𝟐(a−x)2
= 𝐤𝐭 +
𝟏
𝟐a2
8. 𝐤𝐭 =
𝟏
𝟐(a−x)2 -
𝟏
𝟐a2
𝐤 =
𝟏
𝟐𝐭
{
𝟏
(a−x)2 -
𝟏
a2 }
Thus,
k =
𝟏
𝟐𝐭
{
𝐱(𝟐𝐚−𝐱)
a2(a−x)2
} …… (4)
Eq(4)represents the expression for rate
constant of third order reaction.
𝐤 =
𝟏
𝟐𝐭
{
a2− a2−𝟐𝐚𝐱+x2
a2(a−x)2 }
9. * Characteristics of 3rd order reaction:-
1) The velocity constant (k) depends on the unit
of concentration terms.
2) Half–Life of Reaction:
The time (t1/2) for completion of half of the
reaction can be calculated as,
We have, k =
𝟏
𝟐𝒕
{
𝒙(𝟐𝒂−𝒙)
a2(a−x)2 }
Iet =
𝟏
𝟐𝑲
{
𝒙(𝟐𝒂−𝒙)
a2(a−x)2 } …….. (A)
When, t = t1/2, x =
𝒂
𝟐
eq.(A) becomes,
11. Note:
“Time required for the concentration of a reactant
to decrease to half its initial value is called half life
of reaction.”
Que:-
Show that for 3 𝐫𝐝order reaction, the time
required to complete any definite fraction of the
reaction is inversely proportional to the square of
the initial concentration of reactant.
12. 3) Unit of k:-
We have, k =
𝟏
𝟐𝒕
{
𝒙(𝟐𝒂−𝒙)
a2(a−x)a2 }
k =
𝟏
𝒕𝒊𝒎𝒆
{
(𝒄𝒐𝒏𝒄𝒆𝒏𝒕𝒓𝒂𝒕𝒊𝒐𝒏)×(𝒄𝒐𝒏𝒄𝒆𝒏𝒕𝒓𝒂𝒕𝒊𝒐𝒏)
( 𝒄𝒐𝒏𝒄𝒆𝒏𝒕𝒓𝒂𝒕𝒊𝒐𝒏)2×(𝒄𝒐𝒏𝒄𝒆𝒏𝒕𝒓𝒂𝒕𝒊𝒐𝒏)2 }
k =
𝟏
𝒕𝒊𝒎𝒆
×
𝟏
( 𝒄𝒐𝒏𝒄𝒆𝒏𝒕𝒓𝒂𝒕𝒊𝒐𝒏)2 Ie. k=
𝟏
( 𝒄𝒐𝒏𝒄𝒆𝒏𝒕𝒓𝒂𝒕𝒊𝒐𝒏)2×
𝟏
𝒕𝒊𝒎𝒆
ie. k=(concentration) -2× (time)-1
In C.G.S. unit, k expressed in mol-2.litre2min-1.
In SI. Unit, k expressed in mol−2.(dm3)2.s-1
ormol-2(dm6).s-1.
For nth order k=(concentration)1-n (time)-1
13. * Examples of third order reaction:-
1) Reaction of nitric oxide with oxygen or hydrogen or
chlorine / bromine.
a) 2NO (g) + O2 (g) ⟶ 2NO2 (g)
b) 2NO (g) + Cl2 (g) ⟶ 2NOCl(g)
c) 2NO (g) + H2 (g) ⟶ N2O (g)+ H2O (g)
2) Oxidation of ferrous sulphate in water.
3) 2FeCl3 (aq) + SnCl2 (aq) ⟶ 2FeCl2 + SnCl4
4) The Reaction between benzoyl chloride and alcohol in
ether solution.
5) The Reaction between iodite and ferric ions in aq.
Solution. Fe+3 (aq) + 2I- (aq) ⟶ product
6) The decomposition of hypobromous acid in the pH
range 6.4 to 7.8
14. * Method to determine the order of reaction:-
“The number of molecules or atoms whose
concentration changes during the reaction is called
Order of reaction.”
Or “The number of molecules or atoms whose
concentration determines the rate of reaction is
called Order of reaction.”
(1) Van’t Hoff’s differential method (1884):-
This method involves determination of rates
(dc/dt) by measuring slopes of concentration (c) vs.
time (t) curves
For nth order reaction, we have,
….(1). C = concentration.Rate =
–𝒅𝒄
𝒅𝒕
= K.cn
15. For concentrations, c1& c2 we have,
–𝒅𝒄₁
𝒅𝒕
= k. cn
1…. (2) and
–𝒅𝒄₂
𝒅𝒕
= k. cn
2.... (3)
Taking ratio of the eqns (2) & (3)
−𝒅𝒄1 /𝒅𝒕
−𝒅𝒄2 /𝒅𝒕
= (
𝒄1
𝒄 𝟐
)n ……… (4)
Taking logarithm of the eq. (4)
log
−𝒅𝒄1 /𝒅𝒕
−𝒅𝒄2 /𝒅𝒕
= n log {
𝒄1
𝒄 𝟐
} ……… (5)
Thus order of reaction (n) is calculated as
𝒏 =
𝐥𝐨𝐠(−𝒅𝒄1 /𝒅𝒕) − 𝐥𝐨𝐠(−𝒅𝒄2 /𝒅𝒕)
𝐥𝐨𝐠 𝒄1 − 𝐥𝐨𝐠 𝒄2
16. (2) Integrated rate expression method:-
(1) In thismethod, the values of ‘x’at various time
interval ‘t’ determined experimentally. (x = amount of
reactant decomposed).
(2) These values substituted in rate constant equations
of first, second and third order reactions.
(3) (i) For 1st order reaction, k =
𝟐.𝟑𝟎𝟑
𝒕
log10
𝒂
(𝒂–𝒙)
(ii) For 2nd order Rean, k =
𝟏
𝒕
𝒙
𝒂 (𝐚–𝐱)
(For equal conn)
k =
𝟐.𝟑𝟎𝟑
𝒕(𝒂–𝒃)
log10
𝒃(𝒂–𝒙)
𝒂(𝒃–𝒙)
(For unequal conn)
(iii) For 3rd order Rean, k =
𝟏
𝟐𝒕
𝒙(𝟐𝐚–𝐱)
𝒂² (𝐚–𝐱)²
(For equal conn)
17. (4) The order of reaction (n) is determined by the
equation which gives satisfactory constant value of
velocity constant (K).
(5) This is method of trial and error but it is
extensively used.
18. (3) Half-life method (Fractional change method) or
(method of equifractionalparts).
In this method time (t) taken to complete a definite
fraction of the reaction is calculated.
If t = time required for completion of definite fraction of
reaction.
a = initial concentrations of a reactant.
Then,
a) For 1st order reaction, t α
𝟏
𝒂°
ie t is independent on
initial concentration.
b) For 2nd order reaction, t α
𝟏
𝒂
c) For 3rd order reaction,t α
𝟏
𝒂²
d) In general for nth order reaction, t α
𝟏
𝒂ⁿ⁻¹
19. If, t1& t2 times required for completion of same
fraction of reaction with different initial concna1&
a2respectively. And ‘n’ is order of reaction.
Then,
andie.
Taking log, log10[
𝒕₁
𝒕₂
] = (n–1) log10[
𝒂₂
𝒂₁
]
𝒍𝒐𝒈₁₀
[
𝒕₁
𝒕₂
]
𝒍𝒐𝒈₁₀
[
𝒂₂
𝒂₁
]
= n–1
i.en = 1 +
𝒍𝒐𝒈₁₀
[
𝒕₁
𝒕₂
]
𝒍𝒐𝒈₁₀
[
𝒂₂
𝒂₁
]
…… (A)
[
𝒕₁
𝒕₂
] = [
𝒂₂
𝒂₁
]n–1
t1 α
𝟏
𝒂₁ⁿ⁻¹
t2 α
𝟏
𝒂₂ⁿ⁻¹
20. To get values of a1 & a2 , plot graph of ‘x’ vs ‘t’
And from eq.(A) ‘n’ can be calculated.
21. Effect of temperature on the rate of
reaction:-
Rise in temperature
(1) Initiate the reaction.
(2) Increase the rate of reaction.
22. (A) Temperature coefficient:-
It has been found that generally rate of reaction
and rate constant increases with increase in temperature.
For homogeneous reaction, rate and rate (velocity)
constant of reaction get approximately doubled or tripled
for every 100 C rise in temperature. This is generally
expressed in the form of temperature coefficient.
“The ratio of rate constants of a reaction at two
different temperatures which differ by 100c is called
temperature coefficient.”
Where,
Kt = velocity constant at t0c. Kt+10 = velocity constant at t0c
Temperature coefficient =
𝑲(𝒕+𝟏𝟎)
𝑲𝒕
≈ 2 or 3
23. (B) Arrhenius Equation:-
Arrhenius suggested as simple relationship
between the rate constant (k) and the temperature (T)
Eq. (1) is called the Arrhenius equation.
A = constant called frequency factor.
K = velocity constant. R = gas constant.
Ea= activation energy. T = Absolute temperature.
E = logarithmic base = 2.718
Alternately we can write,
k=A.e–Ea/RT ….... (1)
𝒍𝒐𝒈 𝒆
𝒌
𝒅𝒕
=
𝑬a
𝑹𝑻²
……. (2)
24. Integrating eqn (2), we get, Assume Ea as constant.
or ... (3)
C & C’ are constants
Now,log10k =
–𝑬a
𝟐.𝟑𝟎𝟑𝑹
×
𝟏
𝑻
+ C’
Is a eqn of straight line. ie.y = mx + c
Hence, graph of logeK vs
𝟏
𝑻
, is a straight line.
Slop = m =
− 𝑬a
𝟐.𝟑𝟎𝟑 𝑹
Ea= – 2.303 × R × slop
loge k =
–𝑬a
𝑹𝑻
+ C log10 k =
–𝑬a
𝟐.𝟑𝟎𝟑𝑹𝑻
+ C’
25. On integrating eqn (2) between the limit
K = K1 at T = T1 and K = K2 at T = T2
We get,
log10
𝒌₂
𝒌₁
=
𝑬a
𝟐.𝟑𝟎𝟑𝑹
[
𝟏
𝑻₁
–
𝟏
𝑻₂
]
Ie. log10
𝒌₂
𝒌₁
=
𝑬a
𝟐.𝟑𝟎𝟑𝑹
[
𝑻₂– 𝑻₁
𝑻₁. 𝑻₂
]
From this equation, Eacan be calculated.
26. (C) Energy of activation (Ea ):-
According to concept of activation, reactant does not
pass directly to product.
Arrhenius suggested that, before react, colliding
molecule must be activated by absorbing minimum
amount of energy called Activation energy.
Astemperature increases the number of such active
molecules also increases.
Thus,“the minimum amount of energy
required for the collision between the molecules to
be effective is called Energy of activation.”
27. Energy of activation (Ea) can be calculated by
Arrhenius equation as,
𝒍𝒐𝒈𝓮 𝒌
𝒅𝒕
=
𝑬𝒂
𝑹𝑻²
Orlog10
𝒌₂
𝒌₁
=
𝑬𝒂
𝟐.𝟑𝟎𝟑𝑹
[
𝑻₂– 𝑻₁
𝑻₁. 𝑻₂
]
Energy of activation (Ea) depends on the nature of
reactants.
* Slow reactions have high Ea.
* Fast reactions have low Ea.
28. Collision Theory Of Chemical Kinetics (Or)
Kinetic Molecular Theory Of Rates Of
Reactions:- (Max Trautzb and William Lewis)
1) This theory is based on kinetic theory of gases.
2) According to this theory, to occur chemical
reactions there should be collision between
reacting molecules.
3) However all the collisions are not effective to
produce chemical change.
29. 4) Hence, Arrhenius suggested that, before
formation of product colliding molecule must be
activated by absorbing minimum amount of
energy called Activation energy (Ea).
So that they can pass over energy barrier existing
between reactants and product. (fig A)
30. 5) If reacting molecule colloids with insufficient
energy can’t pass over the energy barrier.
However if the reacting molecule colloids with
sufficient energy can pass over the energy barrier &
get activated. And hence converted into product.
(Fig B)
31. 6) This Threshold Energyor minimum energy
necessary to allow a reaction to occur is called
energy of activation (Ea).
Thus energy of activation is the minimum energy
required for the collision between the molecules
to be effective.
7) Slowreactions have high Eawhile Fastreactions
have low Ea.
8) As temperature increases, effective collision
increase. Hence activated molecule increases and
rate of reaction increases.
Note:- The magnitude of Ea depends on the
nature of reactants.
32. Transition state theory or Activated complex
theory or Theory of absolute reaction rate:-
(Henry Erying 1935)
1) This theory is applicable to gas and liquid
phase reaction. It is very complicated theory.
2) According to this theory, “Before
reacting molecules changes into products,
they form transition state or activated
complex which is unstable and decompose to
form product.”
33. 3) In this theory it is supposed that, as two
reacting approach each other, their potential
energy increases and reaches to maximum.(fig).
34. 4) This lead to the formation of activated
complex. This activated complex is unstable and
decomposes to form product or collapse back
into reactants. (Fig)
35. 5) Example: Consider the reaction X + YZ XY + Z
Initially P.E. (E1) is unaffected because X and YZ are far
away from each other. When X approaches to YZ, the P.E.
increases and reaches to maximum (fig), which corresponds
to activated complex X-Y-Z. This activated complex is
unstable and decomposes to form product XY and P.E. drop
to E2.
Note:
The minimum amount of energy required by the colliding
molecules to yield the products is called Threshold Energy.
Energy of activation Ea= P.E. of activated complex - P.E. of reactants