chemical kinetics Flashcards

12838901374	mechanism	series of elementary steps that make up an overall reaction	0
12838901375	intermediate	does not appear in the overall reaction (is created and consumed in overall reaction).	1
12838901376	rate-determining step	slowest step in the mechanism. determines overall reaction rate	2
12838901377	collision theory	the rate of a reaction is proportional to the number of collisions per second between reacting molecules	3
12838901378	an effective collision occurs when...	molecules collide at the correct orientation and have sufficient energy	4
12838901379	activation energy	the minimum energy of collision necessary for a reaction to take place. (Ea) the energy required to reach the transition state	5
12838901405	Arrhenius equation, which embodies collision theory		6
12838901380	frequency factor	measure of how often molecules in the reaction collide (A)	7
12838901381	As temperature increases, the rate constant...	increases	8
12838901382	the frequency factor can be increased by...	the number of molecules/concentration	9
12838901383	transition state	old bonds are weakened and new bonds are beginning to form. highest energy state.	10
12838901384	transition states vs intermediates	transition states are theoretical constructs that exist at the point of max energy.	11
12838901385	4 factors that affect reaction rate	concentrations, temperature, medium, catalyst	12
12838901386	as reactant concentrations increase, reaction rate....	increases (more mlcs, more collisions, higher frequency factor) UNLESS its a zero-order reaction	13
12838901387	as temperature increases, reaction rate....	increases (more kinetic energy, more mlcs with enough energy to surpass Ea) BUT too much heat may cause a catalyst to denature.	14
12838901388	how does medium affect reaction rate?	some mlcs are more likely to react in an aqueous or non-aqueous solvent. physical state can also have an effect. Typically, polar solvents are preferred because mlcr dipole tends to polarize and weaken bonds of reactants, making reaction go faster	15
12838901389	catalyst	substance that increases reaction rate without being consumed in the reaction, interact with reactants by absorption or creation of intermediates, stabilizing them and reducing activation energy.	16
12838901390	homogeneous catalysis	catalyst is in the same phase (solid, liquid, gas)	17
12838901391	heterogeneous catalysis	catalyst is in a different phase (solid, liquid, gas)	18
12838901392	limitations of catalysts	cant effect the free energies of reactants or products cant effect the equilibrium position or Keq	19
12838901393	rate law expression	k= rate constant m,n= orders of reactants measured in M/s determined experimentally	20
12838901394	zero-order reaction	rate of formation of the product is independent if the changes in concentration of the reactants. only way to change the rate of a zero-order reaction is with a catalyst	21
12838901395	first order reaction	rate is directly proportional to only one reactant.	22
12838901396	second order reaction	rate is proportional to either two reactants or the square concentration of one.	23
12838901397	mixed-order reaction	non integer orders	24
12838901398	plotting a first order reaction	Ln[A]t=-kt+Ln[A]o y=mx+b y axis: Ln[A] x axis: t slope: -k linear graph	25
12838901399	half-life	time to get to half the initial concentration	26
12838901406	half-life of a first order reaction		27
12838901400	plotting a second order reaction	1/[A]t=kt+1/[A]o y axis: 1/[A] x axis: t slope: k	28
12838901407	half life of a second order reaction		29
12838901401	molar absorptivity in spectroscopy	a measure of how well a chemical species absorbs a given wavelength of light	30
12838901402	0% transmittance in spectroscopy	If all the light is absorbed in a solution	31
12838901403	The average rate of disappearance of ozone in the reaction 2O3 --> 3O2 is found to be 8.76 × 10¯3 atm over a certain interval of time. What is the rate of appearance of O2 during this interval?	13.1 × 10¯3 atm/s	32
12838901404	What's the rate law for: X → Y + Z	Rate = k[X]	33