Here are the steps to determine the order of the reaction:
1) Plot [X] vs time on a graph. You will get a straight line through the origin, indicating the reaction is first order.
2) Take the log of both sides of the rate law equation:
Rate = k[X]
Log(Rate) = Log(k[X])
3) Plot log(Rate) vs log([X]). You will get a straight line with a slope of 1, confirming the reaction is first order.
Therefore, based on the experimental data and analysis, this reaction is first order with respect to X.
a detailed description of the chapter chemical kinetics (physical chemistry) including different problems by Dr. Satyabrata Si from KIIT school of biotechnology
Chemical kinetics: the study of how fast chemical reactions occur.Specifically:
Rates of consumption of reactants and formation of products.
Response of chemical rates to changes in rxn conditions.
Identification of steps through which rxn takes place.
Reasons for study
Prediction of how quickly a rxn approaches equilibrium.
Understanding or elucidation of rxn mechanisms.
My notes for A2 Chemistry Unit 4, typed by me and compiled from various sources. I cannot trace back where everything came from but again shall any intellectual property rights be violated, please comment /contact me and I will try my best to rectify them as soon as possible.
a detailed description of the chapter chemical kinetics (physical chemistry) including different problems by Dr. Satyabrata Si from KIIT school of biotechnology
Chemical kinetics: the study of how fast chemical reactions occur.Specifically:
Rates of consumption of reactants and formation of products.
Response of chemical rates to changes in rxn conditions.
Identification of steps through which rxn takes place.
Reasons for study
Prediction of how quickly a rxn approaches equilibrium.
Understanding or elucidation of rxn mechanisms.
My notes for A2 Chemistry Unit 4, typed by me and compiled from various sources. I cannot trace back where everything came from but again shall any intellectual property rights be violated, please comment /contact me and I will try my best to rectify them as soon as possible.
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.
Chemical Kinetics & Rate of a chemical reaction.pptxDidarul3
Rate of reaction
✓Zero order reaction
✓1st order reaction
✓2nd order reaction
✓Theories of chemical reaction rate
Determination of order of reaction
Factors that influence reaction rates
Activation energy
Activation complex
This features the types of chemical reactions: Combustion, Neutralization, Precipitation and RedOx Reactions.
There are sample in each of the type of reaction that can help the learners understand more about each type.
This tackles the basics and the easiest concept of Chemical reactions. This features only the four basic types of chemical reactions: synthesis, decomposition, metathesis, and ion - exchange reaction.
This is a basic concept because there is a pattern to be followed in each type of reaction.
More types of chemical reactions will be given on my next set of presentation entitled, "Everything You Want to Know About Chemical Reactions."
Reproduction of plants and simple animalsRAJEEVBAYAN1
This is a concept that tackles about the different methods of reproduction, asexual and sexual.
This features how organisms reproduce to offspring other than man and higher animals.
This covers the topic on Proteins, in general. This discusses the different amino acids, bonds formed, structure of proteins and also the different chemical reactions involved with it.
This material is a great help for high school students and students taking up medical and science courses.
This tackles the topic on Lipids, generally. This include its uses, structures, metabolism and Chemical reactions involved with it.
This is a great help for learners in Junior High School, senior high school and those who are majoring in Science.
Basics of Chemistry: Chemical stoichiometryRAJEEVBAYAN1
This material presents quantitative method of numerical measurements involved in a chemical reaction.
this involves quantities such as the measures of mass in grams and the amount of substance in moles.
I am hoping that this material will help to make the concept easier.
This showcases the basics of the laws governing behavior of gases which includes:
1. Boyle's Law
2. Charles's Law
3. Gay - Lussac's Law
4. Combined Gas Law
5. Avogadro's Law
6. Ideal Gas Law
7. Dalton's Law on Partial Pressures
8. Graham's Law of Diffusion
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.
Richard's aventures in two entangled wonderlandsRichard Gill
Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
Cancer cell metabolism: special Reference to Lactate PathwayAADYARAJPANDEY1
Normal Cell Metabolism:
Cellular respiration describes the series of steps that cells use to break down sugar and other chemicals to get the energy we need to function.
Energy is stored in the bonds of glucose and when glucose is broken down, much of that energy is released.
Cell utilize energy in the form of ATP.
The first step of respiration is called glycolysis. In a series of steps, glycolysis breaks glucose into two smaller molecules - a chemical called pyruvate. A small amount of ATP is formed during this process.
Most healthy cells continue the breakdown in a second process, called the Kreb's cycle. The Kreb's cycle allows cells to “burn” the pyruvates made in glycolysis to get more ATP.
The last step in the breakdown of glucose is called oxidative phosphorylation (Ox-Phos).
It takes place in specialized cell structures called mitochondria. This process produces a large amount of ATP. Importantly, cells need oxygen to complete oxidative phosphorylation.
If a cell completes only glycolysis, only 2 molecules of ATP are made per glucose. However, if the cell completes the entire respiration process (glycolysis - Kreb's - oxidative phosphorylation), about 36 molecules of ATP are created, giving it much more energy to use.
IN CANCER CELL:
Unlike healthy cells that "burn" the entire molecule of sugar to capture a large amount of energy as ATP, cancer cells are wasteful.
Cancer cells only partially break down sugar molecules. They overuse the first step of respiration, glycolysis. They frequently do not complete the second step, oxidative phosphorylation.
This results in only 2 molecules of ATP per each glucose molecule instead of the 36 or so ATPs healthy cells gain. As a result, cancer cells need to use a lot more sugar molecules to get enough energy to survive.
Unlike healthy cells that "burn" the entire molecule of sugar to capture a large amount of energy as ATP, cancer cells are wasteful.
Cancer cells only partially break down sugar molecules. They overuse the first step of respiration, glycolysis. They frequently do not complete the second step, oxidative phosphorylation.
This results in only 2 molecules of ATP per each glucose molecule instead of the 36 or so ATPs healthy cells gain. As a result, cancer cells need to use a lot more sugar molecules to get enough energy to survive.
introduction to WARBERG PHENOMENA:
WARBURG EFFECT Usually, cancer cells are highly glycolytic (glucose addiction) and take up more glucose than do normal cells from outside.
Otto Heinrich Warburg (; 8 October 1883 – 1 August 1970) In 1931 was awarded the Nobel Prize in Physiology for his "discovery of the nature and mode of action of the respiratory enzyme.
WARNBURG EFFECT : cancer cells under aerobic (well-oxygenated) conditions to metabolize glucose to lactate (aerobic glycolysis) is known as the Warburg effect. Warburg made the observation that tumor slices consume glucose and secrete lactate at a higher rate than normal tissues.
The increased availability of biomedical data, particularly in the public domain, offers the opportunity to better understand human health and to develop effective therapeutics for a wide range of unmet medical needs. However, data scientists remain stymied by the fact that data remain hard to find and to productively reuse because data and their metadata i) are wholly inaccessible, ii) are in non-standard or incompatible representations, iii) do not conform to community standards, and iv) have unclear or highly restricted terms and conditions that preclude legitimate reuse. These limitations require a rethink on data can be made machine and AI-ready - the key motivation behind the FAIR Guiding Principles. Concurrently, while recent efforts have explored the use of deep learning to fuse disparate data into predictive models for a wide range of biomedical applications, these models often fail even when the correct answer is already known, and fail to explain individual predictions in terms that data scientists can appreciate. These limitations suggest that new methods to produce practical artificial intelligence are still needed.
In this talk, I will discuss our work in (1) building an integrative knowledge infrastructure to prepare FAIR and "AI-ready" data and services along with (2) neurosymbolic AI methods to improve the quality of predictions and to generate plausible explanations. Attention is given to standards, platforms, and methods to wrangle knowledge into simple, but effective semantic and latent representations, and to make these available into standards-compliant and discoverable interfaces that can be used in model building, validation, and explanation. Our work, and those of others in the field, creates a baseline for building trustworthy and easy to deploy AI models in biomedicine.
Bio
Dr. Michel Dumontier is the Distinguished Professor of Data Science at Maastricht University, founder and executive director of the Institute of Data Science, and co-founder of the FAIR (Findable, Accessible, Interoperable and Reusable) data principles. His research explores socio-technological approaches for responsible discovery science, which includes collaborative multi-modal knowledge graphs, privacy-preserving distributed data mining, and AI methods for drug discovery and personalized medicine. His work is supported through the Dutch National Research Agenda, the Netherlands Organisation for Scientific Research, Horizon Europe, the European Open Science Cloud, the US National Institutes of Health, and a Marie-Curie Innovative Training Network. He is the editor-in-chief for the journal Data Science and is internationally recognized for his contributions in bioinformatics, biomedical informatics, and semantic technologies including ontologies and linked data.
(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.
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.
Nutraceutical market, scope and growth: Herbal drug technologyLokesh Patil
As consumer awareness of health and wellness rises, the nutraceutical market—which includes goods like functional meals, drinks, and dietary supplements that provide health advantages beyond basic nutrition—is growing significantly. As healthcare expenses rise, the population ages, and people want natural and preventative health solutions more and more, this industry is increasing quickly. Further driving market expansion are product formulation innovations and the use of cutting-edge technology for customized nutrition. With its worldwide reach, the nutraceutical industry is expected to keep growing and provide significant chances for research and investment in a number of categories, including vitamins, minerals, probiotics, and herbal supplements.
2. OVERVIEW
For a chemical reaction to be feasible, it must occur
at a reasonable rate.
Consequently, it is important to be bale to control
the rate of reaction..
Most often, this means making it occur more
rapidly.
When you carry out a reaction in a laboratory, you
want to take place quickly.
A research chemist trying to synthesize anew drug
has the same objective.
Sometimes thought, it is desirable to reduce the
rate of reaction.
3. Meaning of Reaction Rate
The rate of reaction is a positive quantity that expresses
how the concentration of the reactant or product
changes in time.
To illustrate better, consider the reaction:
N2O5 (𝑔) → 2NO2 (g) +
1
2
O2 (g)
The concentration of Dinitrogen pentoxide decreases
with time; the concentration of Nitrogen dioxide and
Oxygen gas increase.
This is because these species have different coefficients
in the balanced equation, the concentration do not
change at the same rate.
4. Meaning of Reaction Rate
The graph shows the changes
in reactant and product
concentrations with time for
the decomposition reaction of
Dinitrogen pentoxide to
Nitrogen dioxide and Oxygen
gas.
The concentrations of NO2 and
O2 increase with time, whereas
N2O5 decreases.
5. Meaning of Reaction Rate
When one mole of N2O5 decomposes, two moles of
NO2 and one – half mole of O2 are formed:
−∆ N2O5 =
∆ NO2
2
=
∆ O2
1
2
Where Δ[ ] refers to the change in concentration in
moles per liter (or molar concentration, M).
The minus sign in front of N2O5 term is necessary
because it [N2O5] decreases as the reaction takes
place; the numbers on the right (2, ½) are the
coefficients of these species in the balanced
equation.
6. Meaning of Reaction Rate
The rate of reaction can now be defined by dividing by
the change in time, Δt:
rate =
−∆ N2O5
∆t
=
∆ NO2
2∆t
=
∆ O2
1
2
∆t
More generally, for the reaction
𝑎A + 𝑏B → 𝑐C + 𝑑D
Where A, B, C and D represent substances in the gas
phase or in aqueous solution, and a, b, c and d are their
balanced equation, then
rate =
−∆[A]
𝑎∆t
=
−∆[B]
𝑏∆t
=
∆[C]
𝑐∆t
=
∆[D]
𝑑∆t
7. Meaning of Reaction Rate
Let’s have an example:
Molecular nitrogen is disappearing at the rate of
0.1M per minute. What will be the concentration of
ammonia after 1 hour?
N2 + 3H2 → 2NH3
rate =
−∆ N2
∆t
=
−∆[H2]
3∆t
=
∆[NH3]
2∆t
= 0.1𝑀/min
0.1𝑀
min
=
∆[NH3]
2(60min)
∆ NH3 = 0.1𝑀 2 60 = 𝟏𝟐𝑴
8. Meaning of Reaction Rate
Try another example:
1. For the oxidation of Ammonia:
4NH3 + 3O2 → 2N2 + 6H2O
When N2 was found to have a rate of 0.24 M/s, at what rate does water form?
At what rate did ammonia being consumed?
2. Consider the reaction in aqueous solution below:
5Br(aq)
−1
+ BrO3 (aq)
−1
+ 6H(aq)
+1
→ 3Br2 (aq) + 3H2O(l)
If the rate of disappearance of Br–(aq) at a particular moment during the
reaction is 3.5 × 10−4M/s, what is the rate of appearance of Br2(aq) at that
moment?
9. Measurement of Rate
For the reaction:
N2O5 (𝑔) → 2NO2 (g) +
1
2
O2 (g)
the rate could be determined by measuring:
▪ The absorption of visible light by the NO2 formed;
this species has a reddish – brown color, whereas
N2O5 and O2 are colorless.
▪ The change in pressure that results from the
increase in the number of moles of gas (1 mol
reactant ⟶ 2 ½ mol product).
10. Reaction Rate and Concentration
The higher the concentration of starting materials, the more
rapidly a reaction takes place.
Pure H2O2, in which its molecular concentration is about 40 M,
is an extremely dangerous substance.
In the presence of trace impurities, it decomposes explosively:
H2O2 (l) → H2O(g) +
1
2
O2 (g)
At a rate too rapid to measure.
The hydrogen peroxide you buy in the drugstore is a dilute
aqueous solution in which [H2O2]= 1M.
At this relatively low concentration, decomposition is so slow
that the solution is stable for several months.
11. Reaction Rate and Concentration
The dependence of reaction rate on concentration is
readily explained.
Reactions occur as the result of collision between reactant
molecules.
The higher the concentration of molecules, the greater the
number of collisions in unit time and hence the faster the
reaction.
As reactants are consumed, their concentration drop,
collisions occur less frequently, and reaction rate
decreases.
12. Rate Expression and Rate Constant
The dependence of reaction rate is readily determined for the
decomposition of N2O5.
In the figure on the right shows what happens when reaction
rate is plotted versus [N2O5].
As you would expect, rate increases as concentration increases,
going 0 when [N2O5] = 0 t about 0.00038M/s when [N2O5] =
0.08 M.
Moreover, as you can see, the plot of rate versus concentration
is a straight line through the origin, which means that the rate
must be directly proportional to the concentration:
rate = 𝑘[N2O5]
13. Rate Expression and Rate Constant
This equation is referred to as the rate expression
for the decomposition of N2O5.
It tells how the rate of reaction
N2O5 (𝑔) → 2NO2 (g) +
1
2
O2 (g)
depends on the concentration of the reactant.
The proportionality constant, k, is called a rate
constant.
It is dependent on the other quantities in the
equation.
14. Order of Reaction involving a Single Reactant
Rate expressions have been determined by experiment for a large number of
reactions.
For the process
A → 𝑝𝑟𝑜𝑑𝑢𝑐𝑡𝑠
The rate expression has a general form: 𝒓𝒂𝒕𝒆 = 𝒌[𝐀]𝐦
The power to which the concentration of reactant Ais raised in the rate
expression is called the order of the reaction, m.
If m = 0, the reaction is said to be “zero – order.”
If m = 1, the reaction is “first - order”; if m = 2, it is “second order”; and so on.
Ordinarily, the reaction order is integral (0, 1,2, …), but fractional orders, such as
3/2 are possible.
15. Order of Reaction involving a Single Reactant
The order of reaction must be determined
experimentally; it cannot be deduced from the
coefficients in the balanced equation.
This must be true because there is only one reaction
order, but there are many ways in which the equation for
the reaction can be balanced.
For example: N2O5(𝑔) → 2NO2(g) +
1
2
O2(g)
To describe the decomposition of N2O5, it could have
been: 2N2O5(𝑔) → 4NO2(g) + O2(g)
The reaction is still first – order no matter how the
equation is written.
16. Order of Reaction involving a Single Reactant
One way to find the order of a reaction s to measure the initial rate (i.e., the
rate at t=0) as a function of the concentration of the reactant.
Suppose that we make up two different reaction mixtures differing only in
the concentration of reactant A.
We now measure the rates at the beginning of the reaction, before the
concentration of A has decreased appreciably.
This gives two different initial rates (rate1, rate2) corresponding to two
different starting concentrations of A, [A]1 and [A]2.
From the rate expression, 𝐫𝐚𝐭𝐞𝟐 = 𝒌[𝐀]𝟐
𝒎
and 𝐫𝐚𝐭𝐞𝟏 = 𝒌[𝐀]𝟏
𝒎
Dividing the second by the first gives:
𝐫𝐚𝐭𝐞𝟐
𝐫𝐚𝐭𝐞𝟏
=
[𝐀]𝟐
𝒎
[𝐀]𝟏
𝒎 =
[𝐀]𝟐
[𝐀]𝟏
𝒎
17. Order of Reaction involving a Single Reactant
Example:
Acetaldehyde, CH3CHO, occurs naturally in oak and
tobacco leaves, and is present in automobile and diesel
exhaust. The initial rate of decomposition of
acetaldehyde at 600OC
CH3CHO → CH4 + CO
Was measured at a series of concentrations with the
results on the table shown.
Using these data, determine the reaction order (m) in
the equation: 𝑟𝑎𝑡𝑒 = 𝑘[CH3CHO]𝑚
.
Rate [CH3CHO]
0.34 M/s 0.20 M
0.76 M/s 0.30 M
1.4 M/s 0.40 M
2.1 M/s 0.50 M
18. Order of Reaction involving a Single Reactant
Solution:
𝐫𝐚𝐭𝐞𝟐
𝐫𝐚𝐭𝐞𝟏
=
[𝐀]𝟐
𝒎
[𝐀]𝟏
𝒎 =
[𝐀]𝟐
[𝐀]𝟏
𝒎
rate2
rate1
=
0.76
0.34
= 2.2
rate2
rate1
=
CH3CHO 2
CH3CHO 1
𝑚
= (
0.30
0.20
)𝑚 = (1.5)𝑚
2.2 = (1.5)𝑚
𝑙𝑜𝑔2.2 = 𝑙𝑜𝑔(1.5)𝑚
𝑙𝑜𝑔2.2 = 𝒎𝑙𝑜𝑔(1.5)
𝑚 =
𝑙𝑜𝑔2.2
𝑙𝑜𝑔1.5
=
0.3424
0.1761
= 1.9 ≅ 𝟐
The reaction is second order.
Rate [CH3CHO]
0.34 M/s 0.20 M
0.76 M/s 0.30 M
1.4 M/s 0.40 M
2.1 M/s 0.50 M
19. Order of Reaction with More than 1 Reactants
Many reactions involve more than 1 reactant.
For the reaction of two species A and B,
𝑎A + 𝑏B → 𝑝𝑟𝑜𝑑𝑢𝑐𝑡𝑠
The general form of the rate expression is: 𝑟𝑎𝑡𝑒 = 𝑘[A]𝑚
×
[B]𝑛
In this equation m is referred to as “the order of the reaction
with respect to A.”
Similarly, n is “the order of the reaction with respect to B.”
The overall order of the reaction is the sum of the exponents,
m+n.
If m=1, n=2, then the reaction is first order in A, second in B
and third – order – overall.
20. Order of Reaction with More than 1 Reactants
When more than one reactant is involved, the order can be
determined by holding the initial concentration of one
reactant constant while varying that of the other reactant.
From rates measured under these conditions, it is possible to
deduce the order of the reaction with respect to the reactant
whose initial concentration is varied.
To see how to do this, consider the reaction between A and B
referred.
Suppose we run two different experiments in which the
initial concentrations of A differ ([A]1, [A]2) but that of B held
constant at [B]. Then,
𝑟𝑎𝑡𝑒1 = 𝑘[A]1
𝑚
× [B]𝑛
𝑟𝑎𝑡𝑒2 = 𝑘[A]2
𝑚
× [B]𝑛
21. Order of Reaction with More than 1 Reactants
Dividing the second equation by the first,
𝑟𝑎𝑡𝑒2
𝑟𝑎𝑡𝑒1
=
𝑘[A]2
𝑚
× [B]𝑛
𝑘[A]1
𝑚
× [B]𝑛
=
[A]2
𝑚
[A]1
𝑚 =
[A]2
[A]1
𝑚
Knowing the two rates and the ratio of the two
concentrations, we can readily find the value of m.
Example:
Consider the reaction between t-butylbromide and a base
at 55OC: CH3 3CBr + OH−1
→ CH3 3COH + Br−1
A series of experiments is carried out by the results on the
right.
Find the order of reaction with respect to both the
reactant.
Exp [(CH3)3CBr] [OH-1] Rate
M/s
1 0.50 M 0.05 M 0.0
05
2 1.0 M 0.05 M 0.0
1
3 1.50 M 0.05 M 0.0
15
4 1.0 M 0.10 M 0.0
1
5 1.0 M 0.10 M 0.0
1
22. Order of Reaction with More than 1 Reactants
To solve for m,
Rate ratio:
𝑟𝑎𝑡𝑒3
𝑟𝑎𝑡𝑒1
=
0.015
0.005
= 3
Concentration ratio:
[ CH3 3CBr]3
[ CH3 3CBr]1
𝑚
= (
1.5
0.5
)𝑚
= 3𝑚
3𝑚
= 3
log3𝑚
= log3
mlog3=log3
m=1
To solve for n,
Rate ratio:
𝑟𝑎𝑡𝑒5
𝑟𝑎𝑡𝑒2
=
0.010
0.010
= 1
Concentration ratio:
[OH−]5
[OH−]2
𝑚
=
0.20
0.05
𝑚
= 4𝑚
4m=1
log4m=log1
mlog4=log1
m=0
The reaction is first order with respect to t-butylbromide and zero-order
with respect to OH—1.
Exp [(CH3)3CBr] [OH-1] Rate
M/s
1 0.50 M 0.05 M 0.0
05
2 1.0 M 0.05 M 0.0
1
3 1.50 M 0.05 M 0.0
15
4 1.0 M 0.10 M 0.0
1
5 1.0 M 0.10 M 0.0
1
23. Order of Reaction: Your Turn
1. Consider the following hypothetical reaction:
X(g)⟶Y(g)
The disappearance of X is monitored at timed
intervals shown in the table on the right. Assume
that the temperature and volume are kept constant.
Calculate the order of reaction with respect to X.
2. The peroxisulfate ion reacts with the iodide ion
in aqueous solution according to the following
equation: S2O8(𝑎𝑞)
−2
+ 3I(𝑎𝑞)
−1
→ 2SO4(𝑎𝑞)
−2
+ I3(aq)
−1
What is the order of reaction with respect to [S2O8
—
2] and [I—1]?
Expt. [X] Rate
1 0.600M 0
2 0.515M 0.00043 M/s
3 0.425M 0.00018 M/s
4 0.355M 0.00010 M/s
5 0.330M 0.00006 M/s
Expt [S2O8
—2]
(M)
[I—1]
(M)
Rate
(M/min)
1 0.0200 0.0155 1.15x10-4
2 0.0250 0.0200 1.85x10-4
3 0.0300 0.0020 2.22x10-4
4 0.0300 0.0275 3.06x10-4
24. Models for Reaction Rate – Collision Model;
Activation Energy
For every reaction, there is a certain minimum energy that molecules
must possess for collision to be effective.
This is referred to as activation energy.
It has a symbol Ea, and is expressed in kJ/mol.
The collision model of reaction rates just developed can be made
quantitative.
The rate constant for a reaction, k, is the product of three factors:
k = p x Z x f
Where:
▪ p, called a steric factor, considers the fact that only certain
orientations of colliding molecules are likely to lead to reaction.
▪ Z, is the collision frequency, which gives the number of molecular
collisions occurring in unit time at unit concentrations of reactants.
▪ f, the fraction of collisions in which the energy of the colliding
molecules is equal to or greater than Ea. (f=e—Ea/RT)
25. Models for Reaction Rate – Transition-State
Model; Activation Energy Diagrams
The idea of the activated complex was developed by
among others, Henry Erying at Princeton in the 1930s.
It forms the basis of the transition – state model for
reaction rate, which assumes that the activated complex
- is in equilibrium, at low concentrations, with the
reactants.
- May either decompose to products by “climbing” over
the energy barrier, or alternatively, revert back to the
reactants.
The transition- state model is generally somewhat more
accurate than the collision model.
It explains why the activation energy is ordinarily much
smaller than the bond enthalpies in the reactant
molecules.
26. Reaction Rate and Temperature
The rates of most reactions increase as the
temperature rises.
The effect of temperature on reaction rate can be
explained in terms of kinetic theory.
Raising the temperature greatly increases the fraction
of molecules having very high speeds and hence high
kinetic energies most likely to react when they collide.
The higher the temperature, the larger the fraction of
molecules that can provide the activation of energy
required for the reaction.
The increase of fraction of effective collision causes
reaction rate to increase with temperature.
27. Catalysis
A catalyst is a substance that increases the rate of a
reaction without being consumed by it.
It does this by changing the reaction path to one with a
lower activation energy.
The catalyzed path consists of two or more steps in the
catalyzed reaction.
A heterogeneous catalyst is one that is in a different phase
from the reaction mixture.
Most commonly, the catalyst is a solid that increases the rate
of a gas – phase or liquid – phase reaction. An example is a
decomposition of Nitrous oxide on gold:
N2O
Au
N2 +
1
2
O2
28. Catalysis
A homogeneous catalyst is one that is present in the
same phase as the reactants.
It speeds up the reaction by forming a reactive
intermediate that decomposes to give products.
In this way, the catalyst provides an alternative process
of lower activation energy.
Many reactions that take place slowly under ordinary
conditions occur readily in living organisms in the
presence of catalysts called enzymes.
Enzymes are protein molecules of high molar mass.
29. Catalysis
Enzymes, like all other catalysts, lower the activation
energy for reaction.
They can be enormously effective; it is not uncommon
for the rate constant to increase by a factor of 1012 or
more.
However, from a commercial standpoint, enzymes have
drawbacks.
A particular enzyme operates best over a narrow range
of temperature.
An increase in temperature frequently deactivates an
enzyme by causing molecules to “unfold,” changing its
characteristic shape.
30. Reaction Mechanisms
A reaction mechanism is a description of a path, or
sequence of steps, by which the reaction occurs at the
molecular level.
In the simplest case, only a single step is involved.
This is a collision between two reactant molecules.
Reaction mechanisms frequently change with
temperature and sometimes with pressure.
The nature of the rate expression and hence the
reaction order depends on the mechanism by which the
reaction takes place.