
	Where results make sense

Topic: Rate determining step

In the News (Fri 17 Feb 12)

EXECUTIVE POWER

Iran

ANALYSIS

Pakistan

Family compact

	Rate-determining step - Wikipedia, the free encyclopedia
		The rate-determining step is a chemistry term for the slowest step in a chemical reaction because it determines the rate of reaction.
		For this reason it is reflected in the rate equation of a reaction.
		All faster steps do not have any effect on the rate due to it being limited by this step.
	en.wikipedia.org /wiki/Rate-determining_step (112 words)

	Chapter 14, Section 5 (Site not responding. Last check: 2007-10-03)
		This experimental rate law is different from the one obtained by assuming that the reaction occurs by a single elementary step.
		In this case, step 2 is the rate-determining step: The rate at which cars can travel the toll road is limited by the rate at which they can pass through plaza B. In the same way, the slowest step in a multistep reaction determines the overall rate.
		Thus, the rate of the overall reaction equals the rate of step 1, and the rate law of the overall reaction equals the rate law of step 1.
	cwx.prenhall.com /bookbind/pubbooks/blb/chapter14/medialib/blb1405.html (2308 words)

	SparkNotes: Reaction Mechanisms: Mechanisms of Chemical Reactions
		The rate limiting step determines the rate of the reaction because it is the slowest step.
		This reaction is the rate determining step because it is the slowest step.
		The rate of an elementary step is the rate constant for that step multiplied by the concentrations of the reactants raised to their stoichiometric powers.
	www.sparknotes.com /chemistry/kinetics/mechanisms/section1.html (1669 words)

	radicals (Site not responding. Last check: 2007-10-03)
		So the reaction rate is mostly sensitive to energy of the higher transition state leading away from B. This slow reaction is called the rate-determining step.
		Rate determination in a catalytic cycle is actually not so different from that in the consecutive reaction scheme above, the reaction rate is again more sensitive to the rate constant for the slower reaction.
		It may at first seem curious that the rate is relatively insensitive to the rate constant for one of the steps, since cycling of the "machine" requires passing through both steps.
	classes.yale.edu /chem125a/125/kinetics/RadicalKinetics/radicals.html (1257 words)

	Exploring Reaction Mechanisms
		This rate law implies that reactants in the rate-determining step are one molecule of hydrogen peroxide and one iodide ion, or in other words, that the rate-determining step is bimolecular.
		For alcohols in the latter group, the rate-determining step in nucleophilic substitution is bimolecular, implying that both an alcohol molecule and a halide ion are involved in the rate-determining step.
		Such reactions should go at the same rate no matter whether the nucleophile is fast or slow, because the rate is determined by a prior process (separation of water from R-) that does not involve the nucleophile.
	www.usm.maine.edu /chy/manuals/116/text/Sn12.html (2042 words)

	SN1 reaction - LearnThis.Info Enclyclopedia (Site not responding. Last check: 2007-10-03)
		Increasing or decreasing the concentration of that kind of molecule in a closed system changes the rate of the reaction in a direct relationship.
		If the nucleophile B is a neutral molecule (very often it is a solvent molecule), a third step is required to complete the reaction.
		Nucleophilicity is irrelevant in the determining step's rate, in which only the substrate is crucial.
	encyclopedia.learnthis.info /s/sn/sn1_reaction.html (219 words)

	Rate Determining Step and Catalysts (Site not responding. Last check: 2007-10-03)
		The lesson attempts to explain rate determining step, which is the slowest step of a multi-step sequence of steps.
		The rate determining step determines the rate of the entire sequence and is important to understanding chemical reactions as well as aspects of industry, production, and time management.
		At the end of the exercise the students will figure the rate of each individual step and the rate of the total sequence and the rate determining step will be obvious.
	www.iit.edu /~smile/ch9013.html (563 words)

	Outline
		Rate constants are constant for a given reaction at a given temperature.
		Steps after the rate-determining step will not appear in the rate law of a multi-step process.
		At equilibrium rate of the forward reaction equals the rate of the reverse reaction.
	antoine.frostburg.edu /chem/simon/chm133/133outline02.htm (1519 words)

	Rate Determining Step (Site not responding. Last check: 2007-10-03)
		An elementary reaction is a reaction which occurs in a single step and cannot be subdivided into simpler steps.
		In using mechanisms to derive rate laws, the first task is to identify the rate determining slow step.
		Since equation (10) is the rate-determining step, the overall rate can be found from the rate of this step.
	www.scientia.org /cadonline/Chemistry/rateprocess/ratedeterm.ASP (452 words)

	[No title] (Site not responding. Last check: 2007-10-03)
		The rate of an elementary step is equal to the theoretical rate constant for that step multiplied by the concentration (s) of the species involved in the step.
		If the rate of interconversion of conformational forms is rapid relative to the rate of reaction, the reactive conformer is not deducible from knowledge of the most stable conformer alone.
		If the concentration of a reactant species that appears in the reaction stoichiometry is absent in the rate law expression (and cannot be related to concentrations which appear in the rate law expression via equilibria), that species becomes involved in the reaction sequence after the rate determining step.
	www.orgchem.iisc.ernet.in /faculty/um/cd213/kinetics_info_99.html (538 words)

	Abstracts
		A method and apparatus for determining electrokinetic properties of a papermaking furnish includes mixing a sample of furnish in a container with a known amount of a charged additive and then measuring the streaming potential of the resultant ionically modified furnish sample.
		These were (a) the relationship between sizing efficiency and the retention behavior of rosin sizes at the wet end, (b) the effect of pulp beating and fiber fines on the size distribution and sizing properties of paper, and (c) the distribution characteristics of rosin size on pulp fiber surfaces in internal paper sizing.
		Rate laws for detachment and the dependency of rates on the applied shear stress permit one to discriminate between processes limited by viscous flow, Brownian motion, and fluctuations in hydrodynamic forces.
	www4.ncsu.edu /~hubbe/abstracts.htm (10946 words)

	G:\exploring\alkylHalides\nucleophilicsubstitution.htm (Site not responding. Last check: 2007-10-03)
		The overall rate of the reaction is determined by the slowest step of the reaction.
		The rate of the reaction is determined by the highest energy transition state.
		The overall rate of the reaction is controlled by the second step of the reaction (rate determining step).
	people.uis.edu /gtram1/organic/alkylHalides/nucleophilicsubstitution.htm (395 words)

	E1 Reactions (Site not responding. Last check: 2007-10-03)
		This mechanism is a two step process with the rate determining step being an ionization of the halide to produce a carbocation.
		Since the rate determining step is the first one involving only the organic alkyl halide, the reaction is first order in respect to the alkyl halide concentration.
		Since the rate determining step in an E1 reaction occurs before the base is involved in the second step, we would not expect the strength of the base to affect teh rate of an E1 reaction.
	members.aol.com /logan20/e1.html (505 words)

	Electrochemistry E
		The assembly consists of a metal in contact with two slightly soluble salts (one containing the cation of the solid metal, the other the cation to be determined, with both salts having a common anion) immersed in a solution containing a salt of the second metal (e.g., zinc metal---zinc oxalate---calcium oxalate---calcium salt solution).
		However, the equilibrium is a dynamic one, that is, the electrode reaction proceeds at "equal rates" both in the forward and in the reverse direction, resulting in a zero "net" reaction rate and a zero "net" current.
		The rate of the electrode reaction can be expressed as an equivalent current density and the "exchange current density" of a reaction is the current density flowing "equally" in both directions in equilibrium.
	www.corrosion-doctors.org /Dictionary/Dictionary-E.htm (6143 words)

	Compare the rate of hydrolysis of some halogeno-compounds.
		Two species are involved in the rate determining step of the reaction.
		The first step is the rate determining step and a carbocation is formed.
		The rate of reaction is independent of the concentration of hydroxide ion.
	www.coursework.info /i/51806.html (475 words)

	Re: What does the overall reaction order tell us about the reaction?
		The rate is zero-order with respect to bromide because bromide is not involved in the rate-determining step.
		The presence of thiosulphate in two steps of the reaction does not imply that it is directly involved in the second step.
		It would be very unusual for a rate constant to be lowered by increasing temperature, but in this case the rate constant is composed of the equilibrium constant of the fast first step and the rate constant of the rate-determining step.
	www.madsci.org /posts/archives/2000-12/975966744.Ch.r.html (552 words)

	Substitutions and Elimination Pathways (Site not responding. Last check: 2007-10-03)
		Reactions whose rate determining steps produce ions can be enhanced by stabilizing the ions using polar solvents that form a solvent cage around each ion due to di-pole interaction between polar solvent molecules and ions.
		This is due to the fact that in the rate determining step the only reactant is the organic molecule which subsequently ionizes.
		Since the mechanism is concerted (ie: single stepped), both the organic reactant and the nucleophile are involved in the rate determining step.
	members.aol.com /logan20/sn1vssn2.html (1071 words)

	Nucleophilic Substitution & Elimination
		The critical step in this mechanism is the first step, in which the bond between the carbon atom and the halogen leaving group is broken.
		The transition state for this step has the bond stretched far enough that the halide ion is balanced between leaving as a stable chloride or bromide ion or slipping back into a covalent bond.
		We call the step which is slowest the "rate determining step." Notice that the rate determining step for this reaction doesn't involve the nucleophile.
	chemistry2.csudh.edu /rpendarvis/SN1Elim.html (2034 words)

	Reaction Mechanisms - derive rate laws
		If several steps are involved in an overall chemical reaction, the slowest step limits the rate of the reaction.
		Note that the rate law is not derived from the overall equation either.
		In this case, step ii is the rate-determining step, and the rate law is,
	www.science.uwaterloo.ca /~cchieh/cact/c123/ratemech.html (839 words)

	R
		A rate-controlling (rate-determining or rate-limiting) step in a reaction occurring by a composite reaction sequence is an elementary reaction the rate constant for which exerts a strong effect - stronger than that of any other rate constant - on the overall rate.
		In such a case the rate of reaction differs from the rate of increase of concentration of a product P by a constant factor (the reciprocal of its coefficient in the stoichiometric equation, p) and from the rate of decrease of concentration of the reactant A by 1/a.
		A measure of the susceptibility to the influence of substituent groups on the rate constant or equilibrium constant of a particular organic reaction involving a family of related substrates.
	www.chem.qmul.ac.uk /iupac/gtpoc/R.html (2950 words)

	014 Hydraulic Elevator
		If a reaction takes place in a series of steps, the rate of the reaction is determined by the rate of the slowest step.
		For the rate determining step variation, you may wrap tape around one tube to make it slower than the others if the tubes are the same size.
		If b were the rate determining step, then the CO concentration would be part of the reaction's rate law.
	dwb.unl.edu /chemistry/beckerdemos/BD014c.html (1371 words)

	Solutions for Homework Assignment #1 (Site not responding. Last check: 2007-10-03)
		In many cases, a catalyst increases the rate by lowering the activation energy for the reaction.
		When the concentration of CH is increased by a factor of 1.33, the reaction rate increases by a factor of 1.33.
		Step 1: Calculate the concentrations of the components in units of mol/L. The molarities can be calculated by simply dividing the number of moles by the volume of the flask.
	www.nau.edu /~chem/courses/chm152/hw6sol (801 words)

	Reaction Mechanism Assignment (Site not responding. Last check: 2007-10-03)
		The slowest step in a reaction (the rate determining step) determines the overall rate.
		(aq)] would cause the rate to go twice as fast if either step 1 or step 2 were the rate determining step.
		Thus, the rate determining step must be 1.
	www.carlton.paschools.pa.sk.ca /Chemical/chem30/ReactionRate/reactionmechanismassignment.htm (205 words)

	Ch 8 : SN1 mechanism
		1 reaction, the rate determining step is the loss of the leaving group to form the intermediate carbocation.
		Some students fall into the trap of thinking that the system with the less stable carbocation will react fastest, but they are forgetting that it is the generation of the carbocation that is rate determining.
		Since the nucleophile is not involved in the rate determining step, the nature of the nucleophile is unimportant in an S
	www.chem.ucalgary.ca /courses/351/Carey5th/Ch08/ch8-2.html (652 words)

	Electro-Chem-Technic :: Multi-Step Reaction
		The speed of the various steps can be measured, and the rate determining step deduced.
		Furthermore, it is not difficult to relate the current from the cell to the reaction rate.
		You should find that the reaction rate when using methanol is markedly lower than the other two fuels, showing that the step methanol ---> methanal is the rate determining step.
	www.ectechnic.co.uk /exp5.html (554 words)

	Chapter 5 : E1 mechanism
		This implies that the rate determining step of the mechanism depends on the decomposition of a single molecular species.
		Reactivity order : (CH In an E1 reaction, the rate determining step is the loss of the leaving group to form the intermediate carbocation.
		Since the base is not involved in the rate determining step, the nature of the base is unimportant in an E1 reaction.
	www.chem.ucalgary.ca /courses/351/Carey/Ch05/ch5-5.html (459 words)

	KEY
		So, if we plug the rate constant and the initial concentration of NO (if needed) into the expressions for half-life given on the formula page, one of these expressions will give us an answer equivalent to 75.5 years...that expression will be for the correct order of the reaction.
		The second step is slower because it has a higher activation energy than the first step...it is therefore the rate-determining step.
		The overall activation energy of the reaction is the difference between the energy of the highest "hill" the reaction has to "climb" minus the energy of the reactants.
	natsci.edgewood.edu /genchem/IIexam2key.htm (1531 words)

	Pratice Exam 2, October 16, 1997 (Site not responding. Last check: 2007-10-03)
		As the rate law would have the same form no matter which step is rate determining, the dtermination of the experimental rate law would not aid in the detemination of the rate determining step in this mechanism.
		The three factors that will determine the rate of a reaction are the concentration of the reactant molecules, the speed at which the molecule are moving and the orientation of the molecules as they collide.
		Thus, an increase in temperature enhances the reaction rate by increasing both the rate of collision and the percentage of collisions that result in a reaction.
	www.wsu.edu:8080 /~chem338/exams/c338-pa2.htm (1343 words)

	Glossary - R
		Radius Ratio Rules: These can be used to predict the structure which will be adopted by a given set of ions, based on the ratio of the ionic radius of the small ion to that of the large ion.
		Rate Determining Step: Just as a chain is only as weak as its weakest link, a reaction is only as fast as its slowest step - the Rate Determining Step (often abbreviated RDS).
		the molecular speeds are measured, squared and then their mean value is determined.
	www.everyscience.com /Chemistry/Glossary/R.php (578 words)

	Study Questions (Site not responding. Last check: 2007-10-03)
		(14.1) Using MX as your starting complex and Y as the substituting ligand, write a chemical equation describing the rate determining step and the rate law for the step for each type of mechanism.
		be sure to indicate the rate determining step for each.
		determine which complex is more sensitive to changes in the entering group.
	www.users.csbsju.edu /~amckenna/CH34100/341,14study.html (307 words)

Try your search on: Qwika (all wikis)