CHB-201: CHEMICAL KINETCS (Note-1) BSc 2nd Semester- N(D
Chemical kinetics is the branch of physical chemistry which deals with a a first order reaction is a constant. 0. Page 6. Integrated rate expression for ...
CHEMICAL KINETICS
CHEMICAL KINETICS. Objectives. • Order and molecularity. • Kinetics of first and second order reaction. • Pseudo unimolecular reaction. • Arrhenius equation. 3
CHEMICAL KINETICS F.Y.B.Sc I) DEFINITIONS: 1) Chemical
1) Derive an expression for rate constant of a first order reaction. Ans Though two molecules A and B are involved in the reaction the reaction is ...
PHYSICAL B. Sc. I YEAR PHYSICAL CHEMISTRY EMISTRY-I
reaction occurs is called chemical kinetics. Chemical Kinetics is the study The first stage in studying the rate and mechanism of a chemical reaction is the.
Department of Chemistry Work-Load Mr. Nishant B.Sc. 1st Year Title
Title of Paper. Th. P. STATES OF MATTER CHEMICAL KINETICS &. FUNCTIONAL ORGANIC CHEMISTRY. 3. ATOMIC STRUCTURE
Chemical Kinetics What are Chemical Kinetics?
A reaction is zero order in a reactant if the change in concentration of that reactant produces no effect. • A reaction is 1st order if doubling the
B. SC. CHEMISTRY (Subsidiary)
1st Year ( 1st Semester + 2nd Semester). Unit : IC/S – Lab. I + IC/S – Lab Chemical Kinetics : Rate of chemical reaction distinction between order and ...
STATE MODEL SYLLABUS FOR UNDER GRADUATE COURSE IN
1st ed. 2015. 3. Selected Topic in Inorganic Chemistry Mallick
Types of chemical reactions Rate of a reaction Factors affecting rate
(2) Moderate reaction: These reactions proceed with a measurable rates at normal temperature and it is these reactions are studied in chemical kinetics. Mostly
CHB-201: CHEMICAL KINETCS (Note-1) BSc 2nd Semester- N(D
Chemical kinetics is the branch of physical chemistry which deals with a study of the speed of chemical reactions. Such studies also enable us to understand
CHEMICAL KINETICS
CHEMICAL KINETICS. Objectives. • Order and molecularity. • Kinetics of first and second order reaction. • Pseudo unimolecular reaction. • Arrhenius equation.
CHEMICAL KINETICS F.Y.B.Sc I) DEFINITIONS: 1) Chemical
1) Chemical kinetics: It is a branch in physical chemistry which deals with Equation III is the expression for rate constant of first order reaction.
Chemical Kinetics What are Chemical Kinetics?
Chemical Kinetics. Reaction rate is the change in the concentration of a reactant or a product with time (M/s). A. B rate = -. ?[A]. ?t rate = ?[B].
PHYSICAL B. Sc. I YEAR PHYSICAL CHEMISTRY EMISTRY-I
The smallest structural unit of all chemical substances in these states is mentioned to explain the behaviour of the gases called the kinetic theory of ...
Chemical Kinetics - Saurashtra University
She has obtained her B. Sc. M. Sc. (Physical Chemistry) and Ph. D degree from Banaras. Hindu University
CHEMISTRY B.Sc. (FIRST YEAR)
Radioactive decay as a first order phenomenon;. Experimental methods of chemical kinetics: conductometric potentiometric
B. SC. CHEMISTRY (Subsidiary)
scales – the Mulliken Allred – Rochow scales. 1st Year 2nd Semester. Unit : IC/S – 103. 15 L. Chemical Bonding – I. A. General
Chemical Kinetics
Chemical. Kinetics. • calculate the average rate of appearance of B over the time interval from 0 to 40 s. PDF Created with deskPDF PDF Writer - Trial
Types of chemical reactions Rate of a reaction Factors affecting rate
B. Sc. II-Sem. Chemical Kinetics reaction rates is called the chemical kinetics. ... the second order reaction conforms to the first order and is known.
Chemical
KineticsChapter 14
ChemicalKineticsChemistry, The Central Science, 10th editionTheodore L. Brown; H. Eugene LeMay, Jr.;
and Bruce E. Bursten PDF Created with deskPDF PDF Writer - Trial :: http://www.docudesk.com 2Chemical
KineticsKinetics
• Chemical Kinetics is the study of the rate at which a chemical process occurs. • Besides information about the speed at which reactions occur, kinetics also sheds light on the reaction mechanism (exactly howthe reaction occurs). PDF Created with deskPDF PDF Writer - Trial :: http://www.docudesk.com 3Chemical
KineticsFactors That Affect Reaction Rates
• Physical State of the ReactantsIn order to react, molecules must come in contact with each other. If the reaction is happening between a solid and a liquid it will react only on the surface.
The more homogeneous the mixture of reactants, the faster the molecules can react. PDF Created with deskPDF PDF Writer - Trial :: http://www.docudesk.com 4Chemical
KineticsFactors That Affect Reaction Rates
• Concentration of ReactantsAs the concentration of reactants increases, so does the likelihood that reactant molecules will collide.
PDF Created with deskPDF PDF Writer - Trial :: http://www.docudesk.com 5Chemical
KineticsFactors That Affect Reaction Rates
• TemperatureAt higher temperatures, reactant molecules have more kinetic energy, move faster, and collide more often and with greater energy.
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KineticsFactors That Affect Reaction Rates
• Presence of a Catalyst Catalysts speed up reactions by changing the mechanism of the reaction. Catalysts are not consumed during the course of the reaction. PDF Created with deskPDF PDF Writer - Trial :: http://www.docudesk.com 7Chemical
KineticsReaction Rates
Rates of reactions can be determined by
monitoring the change in concentration of either reactants or products as a function of time. PDF Created with deskPDF PDF Writer - Trial :: http://www.docudesk.com 8Chemical
KineticsReaction Rates
In this reaction, the
concentration of butyl chloride,C4H9Cl, was
measured at various times.C4H9Cl(aq)+ H2O(l)¾¾®C4H9OH(aq)+ HCl(aq)
PDF Created with deskPDF PDF Writer - Trial :: http://www.docudesk.com 9Chemical
KineticsThe average rate of the
reaction over each interval is the change in concentration divided by the change in time:Average rate =
D[C4H9Cl]
Dt t2 t1 2 1 X - X ΔXAverage rate = =t -t
Δt PDF Created with deskPDF PDF Writer - Trial :: http://www.docudesk.com 10Chemical
Kinetics
Reaction Rates
C4H9Cl(aq)+ H2O(l)¾¾®C4H9OH(aq)+ HCl(aq)
-40.0905 - 0.10000.0095
Average rate = = - 1.9 x 10
50-0 50
PDF Created with deskPDF PDF Writer - Trial :: http://www.docudesk.com 11Chemical
KineticsReaction Rates
• Note that the average rate decreases as the reaction proceeds. • This is because as the reaction goes forward, there are fewer collisions between reactant molecules.C4H9Cl(aq)+ H2O(l)¾¾®C4H9OH(aq)+ HCl(aq)
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Kinetics
• calculate the average rate of appearance of B over the time interval from 0 to 40 s. PDF Created with deskPDF PDF Writer - Trial :: http://www.docudesk.com 13Chemical
Kinetics
Reaction Rates
• A plot of concentration vs. time for this reaction yields a curve like this. • The slope of a line tangent to the curve at any point is the instantaneous rate at that time.C4H9Cl(aq)+ H2O(l)¾¾®C4H9OH(aq)+ HCl(aq)
PDF Created with deskPDF PDF Writer - Trial :: http://www.docudesk.com 14Chemical
Kinetics
Reaction Rates
• All reactions slow down over time. • Therefore, the best indicator of the rate of a reaction is the instantaneous rate near the beginning.C4H9Cl(aq)+ H2O(l)¾¾®C4H9OH(aq)+ HCl(aq)
PDF Created with deskPDF PDF Writer - Trial :: http://www.docudesk.com 15Chemical
KineticsAverage vs. instantaneous rxn
rate • Average rxn rate • Instantaneous rxn rate (tangent to curve) Usually in chemistry, we are interested in the instantaneous rxn rate at the very beginning (at t = 0)INITIAL REACTION RATE
ΔtΔrate]A[
elapsed timetotalend andrxn of beginningbetween ionconcentrat chemical of change )(reactionofrate=))ΔtΔrate]A[
elapsed short time the timeof periodshort aover ionconcentrat chemical of change )(reactionofrate=)) PDF Created with deskPDF PDF Writer - Trial :: http://www.docudesk.com 16Chemical
Kinetics
Average vs. instantaneous
rxn rate NaHCO3 + citric acid --> sodium citrate + H2O + CO200.20.40.60.811.21.41.61.82
0 0.5 1 1.5 2
time (minutes) concentration (tablet/100 mL) initial [A] = 1 tabletinitial [A] = 2 tabletsAverage rate
Instantaneous
rate at t= 0 (initial rate) PDF Created with deskPDF PDF Writer - Trial :: http://www.docudesk.com 17Chemical
KineticsComparing concentrations
of chemicals in a reactionA --> B
00.20.40.60.811.21.41.61.82
0 0.5 1 1.5 2
time (hours) concentration (mol/L) [A][B]A --> 2 C
00.20.40.60.811.21.41.61.82
0 0.5 1 1.5 2
time (hours) concentration (mol/L) [A][C] PDF Created with deskPDF PDF Writer - Trial :: http://www.docudesk.com 18Chemical
KineticsWhat we"re after in kinetics
• We want to be able to understand and predict how much reactants remain (or products get formed) in a certain amount of time • Change with time is rate • Rate means calculus must be used, so we need to be careful which rate we are talking about • We will use instantaneous rate at the start of a reaction (initial rate) • Several factors affect the rate of a reactionInitial concentration
Temperature
Amount of reactant exposed (surface area)
Presence of a catalyst
• A theory (equations) that predicts kinetics must explain these PDF Created with deskPDF PDF Writer - Trial :: http://www.docudesk.com 19Chemical
Kinetics
Calculate the instantaneous rate of disappearance of C4H9Cl at t= 0 (the initial rate). PDF Created with deskPDF PDF Writer - Trial :: http://www.docudesk.com 20Chemical
Kinetics
Determine the instantaneous rate of disappearance of C4H9Cl at t = 300 s.Answer:1.1 ´10 -4M/s
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Kinetics
Reaction Rates and Stoichiometry
• In this reaction, the ratio of C4H9Cl to C4H9OH is
1:1. • Thus, the rate of disappearance ofC4H9Cl is the same as
the rate of appearance of C4H9OH.C
4H9Cl(aq)+ H2O(l)¾¾®C4H9OH(aq)+ HCl(aq)Rate =-D[C4H9Cl]
Dt =D[C4H9OH] Dt PDF Created with deskPDF PDF Writer - Trial :: http://www.docudesk.com 22Chemical
KineticsReaction Rates and Stoichiometry
• What if the ratio is not1:1?2 HI(g)¾¾®H2(g)+ I2(g)
in such a case , 2 2 HI H I1Rate = - = 2 t t tDD D=D D D
PDF Created with deskPDF PDF Writer - Trial :: http://www.docudesk.com 23Chemical
KineticsReaction Rates and Stoichiometry
• To generalize, then, for the reaction aA + bB cC + dDRate = 1
a D[A] Dt = 1 b D[B] Dt =1 c D[C] Dt 1 d D[D] Dt PDF Created with deskPDF PDF Writer - Trial :: http://www.docudesk.com 24Chemical
KineticsKey points about kinetics so far
• Study the vocabulary • Reaction rate has weird units • Be clear whether you are talking about average reaction rate or instantaneous reaction rate • The equations which we will study all talk about instantaneous reaction rate, most easily measured at the beginning of a reaction (initial rate) • Relating rates at which products appear (+) and reactants disappear (-) has to do with inverse stoichiometriccoefficients • Reaction rate depends on several factors: initial concentration, temperature, surface area of reactants exposed, presence of a catalyst PDF Created with deskPDF PDF Writer - Trial :: http://www.docudesk.com 25Chemical
Kinetics
(a)How is the rate at which ozone disappears related to the rate at which oxygen appears in the reaction (b)If the rate at which O2appears, [O2]/t, is 6.0 ´10-5 M/s at a particular instant, at what rate is O3disappearing at this same time, -[O3] /t? PDF Created with deskPDF PDF Writer - Trial :: http://www.docudesk.com 26Chemical
Kinetics
Answers:(a)8.4 ´10 -7 M/s,(b)2.1 ´10 -7 M/sSAMPLE EXERCISE 14.3 continuedThe decomposition of N2O5proceeds according to the following equation:
If the rate of decomposition of N
2O5at a particular instant in a reaction vessel is 4.2´10-7 M/s, what is the rate
of appearance of (a) NO2, (b) O2?
PDF Created with deskPDF PDF Writer - Trial :: http://www.docudesk.com 27Chemical
KineticsConcentration and Rate
One can gain information about the rate
of a reaction by seeing how the rate changes with changes in concentration. PDF Created with deskPDF PDF Writer - Trial :: http://www.docudesk.com 28Chemical
KineticsConcentration and Rate
Comparing Experiments 1 and 2, when [NH
4+] doubles, the initial rate doubles.NH4+(aq)+ NO2(aq)N2(g)+ 2 H2O(l)
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KineticsConcentration and Rate
Likewise, comparing Experiments 5 and 6,
when [NO2] doubles, the initial rate doubles.
NH4+(aq)+ NO2(aq)N2(g)+ 2 H2O(l)
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KineticsConcentration and Rate
• This meansRate µ[NH4+]
Rate µ[NO2]
Rate µ[NH+] [NO2]
orRate = k[NH4+] [NO2]
• This equation is called the rate law , and kis the rate constant PDF Created with deskPDF PDF Writer - Trial :: http://www.docudesk.com 31Chemical
Kinetics• If you want your concepts to be clearer do the visualizing concepts part of the problems at the back of your chapter. PDF Created with deskPDF PDF Writer - Trial :: http://www.docudesk.com 32Chemical
KineticsRate Law
• An equation that shows how the rate depends on the concentration of the reactants is called the rate law • The exponents tell the order of the reaction with respect to each reactant. • This reaction isFirst-order in [NH
4+]First-order in [NO
2] PDF Created with deskPDF PDF Writer - Trial :: http://www.docudesk.com 33Chemical
KineticsRate Laws
• The overall reaction order can be found by adding the exponents on the reactants in the rate law. • This reaction is second-order overall. PDF Created with deskPDF PDF Writer - Trial :: http://www.docudesk.com 34Chemical
Kinetics• For a general reaction:
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