Examkrackers Chemistry: Lecture 4

what is reaction rate definition

(-1/a)(delta[A]/t) rate at equilibrium is zero for NET reaction rate, but forward and reverse still happening

standard state

(Indicated by not sign!)For a pure substance, the most stable form of the substance at 1 atm and a specified temperature, usually 25°C: for a gas, 1 atm; for a solution, concentration of 1 molarl varies with phase, a set of thermodynamic property values, for a pure solid or liquid the standard state is the reference form of a substance at any chosen temp T and pressure 1bar, reference form is usually the form that is most stable at 1 bar and the chosen temp, for pure gas the reference form must behave like ideal gas all species starting at 1 moles *usually always 25 C

what is standard temp and pressure and standard ambient temp/pressure

(STP) pressure of 1 atm and temp 237 K (0 C) standard ambient temp and pressure (SATP) is pressure 1 atm, temp 298 K (25C)

what are three types of stress that Le Chatliers principle is used for

1. 1. addition or removal of a product or reactant 2. changing the pressureo r volume of the system 3. heating or cooling the system

what are three possible modes/degrees of freedom of translational motion

1. along x axxis 2. along y axis 3. along z axis

what are the two properties used to describe macroscopic state of the system and difference between them

1. extensive 2. intensive extensive properties change with amount, intensive properties the same no matter how much substance is present

what are two requirements for a given collision to initiate reaction

1. relative kinetic energies of colliding compounds but be greater than or equal to threshold activation energy (a measure of velocity) 2. atoms of both molecules must align in specific way for collision to result in reaction, otherwise even with enough eenergy to reaction occurs (both conditions must be met)

what are teh five ways to know what delta H is for a reaciton on MCAT

1. they tell you 2. heat measured with calorimeter and heat is negative delta H 3. intuitive, even if you dont know magnitude you may know combustion releases heat so is negative delta H, same thing for phase changes, ie you have to add heat to melt so positive deltaH 4. given table of bond energies, keep track of bonds broken and formed in reaction, forming bonds releases energy and breaking requires input, you can sum the energy heat absorbed and released in the reaction 5. calculate delta H using standard enthalpies of formation

enthalpy

= U + PV where U is internal energy and PV is pressure/volume

temp dependence for value of rate constant is demonstrated by what equation

Arrhenius equation

how does Le chatliers work in the blood

Co2 converted to protons and bicarbonate by enzyme carbonic anhydrase H20+CO2<--->H2CO3<-->HCO3- + H+ when CO2 accumulates in the tissue the equation shifts right and produces acidic protons, because body must maintain pH within a narrowrange, kidney eliminates excess protons in the blood, similarly relying on equilibriums

enthalpy is

U+PV

does catalyst change activation energy in both directions

YES (but by different amounts)

PV work

a chemical system at reset performs _________ by changing its size or shape using energy from the system

Boltzmann's Constant

a physical constant relating the average kinetic energy of particles in a gas with the temperature of the gas; it is the gas constant R divided by Avogadro's number (1.38x10^-23 J K^-1)

how to solve for change in internal energy

according to first law of thermodynamics delta E = q+ w for heat flow into the system and work done on the system can be rewritten for closed system at rest with no electric or magnetic field, only energy change is internal energy (if no chnge in volume then no work of any kind so deltaU=q) deltaU = q+w where U is internal energy if no change in volume there is no work of any kind and the change in internal energy is equal to heat (deltaU =q)

energy transfer from the system to the surroundings is classified as heat or work according to what

according to the effect on the surroundings rather than the effect on the system (if transfer to surroundings causes random molecular collisions then it is heat, but if transfer to outside causes ordered molecular collisions it is defined as work)

what to do with rate constant for reactions with catalyst

ahve separate rate constants, because castalyst does no prevent the original reaction from proceeding, the total rate is given by teh sum of the rates of both reactions, usually rate of original reaciton is negligable compared to the rate of the catalyzed reaction

if reaction is negative enthalpy and positive entropy is it spontaneous

always

what is haber process

an all gas reaction used to show le chatliers, exothermic creating heat n2 +3H2 --> 2NH3+ heat add different things get different amount of heat

rate law

an expression relating the rate of a reaction to the concentration of the reactants rate forward= kf[A]^a[B]^b incorporates only concentrations of reactants since products tend to start getting reversed, kf is the rate constant for the forward direction a and B are the reaction order of each reaction, can be used to determine how changes in initial concentration affect the reaction rate,, shows rate can be increased by increasing concentration of reactants (makes sense because ore collisions)

work (w)

any active energy transfer that is not heat

when graphing chemical work done how do we show on graph

area under the curve of X=V y=P and area mgh, be familiar with this PV diagram

when does delta u equal delta H

at constant volume delta u =q which means that at constant volume and pressure these are equal

when do you measure product concentration for reaction rate

at initial moments of the reaction because most reactions will quickly start reversing and thus products concentrations are scewed when converted back

describe celcius scale major points

at pressure of 1atm water freezes at 0 and boils 100

why does a reaction move to/stay at equilibrium

because nature tends to increase entropy and eq is point of greatest entropy

what is Newtons law of cooling

bodys rate of cooling is proportional to the temp difference between the body and its environment, when radiation strikes an opaque surface only a fraction is absorbed and the rest is reflected, fraction absorbed is indicated by emissivity of the surface which depends on surface composition

bond breaking vs forming whichrequires energy

bond breaking requires energy bond formation releases energy

which represents internal energy U or E

both can, be used interchangeably

for a multistep reaction how do you determine rate equation

break it down into two or more elementary reactions and slowest of these determines rate equation, slow step determines rate law which is maybe hwy concentratifon of some reactants dont affect reaction rate

what are characteristics of closed systems

can exchange energy but not mass

what are characteristics of open systems

can exxchange both mass and energy with their surroundings

what is wrong with building up intermediates when we have mutation in enzyme that causes build up of intermediate

can often harm intracellular organielles or disrupt equilibria

what are characteristics of isolated systems

cannot exxchange energy or mass with their surroundings

how do catalyzed vs uncatalyzed reactions look different on graph

catalyzed reaction other than being lower, has a dip in middle of it for the intermediates, uncatalyzed reaction is smooth/constant parabola

what main system in our body/plants is catabolic vs anabolic example

cellular respiration is catabolic (breaks glucose into water and CO2 and accompanied by energy release) photosyntehsis opposite of anabolic (water and CO2 combined to form glucosei n endothermic reaction that requires energy input from the sun)

what doe first law of thermodynamics say

change in energy is the sum of heat and work, can get more energy out tha nwhat you put in

what is heat of reaction

change in enthalpy from reactants to products, since enthalpy approximates heat in many reactions in the lab

why is one particular step slower or faster

characteristics of the molecule and their interactions determine rate, ie if one moelcule bulky or sterically hindered it will be harder for other molecules to react with it

in an elementary reaction what do coefficients tell you for reaction

coefficients tell you how many molecuels participate in the reaction collision

absolute zero

coldest temperature, 0 Kelvin, that can be reached; hypothetical temperature at which all molecular motion stops. approxx -237 C, can be determined using volume of an ideal gas because volume vs temp is linear for any givven temp, at some point nbecome liquids at low temp, lines for ressure on the graph though intersects at smae point for all gasses on temp axis

do chemical reactions reverse

complete not possible! but partial YES

what are three ways energy transfer can occur through heat

conduction, convection, radiation

what is the emissivity of any surface

constant between 0-1, specific to given objject

change in enthalpy is

cosntant pressure as the heat of reaction

what is vibrational energy

created by back and forth motion of atoms within a molecule, makes an insignificant contribution to internal energy for light diatomic molecules as temperatures below a few hundred Kelvin

what is intermolecular potential energy

created by intermolecular forces between molecular dipoles, makes only small contribution to internal energy for a typical gas at room temp, but at higher pressures becomes significant, makes up a substantial portion of internal energy for liquids and solids

what is translational energy

created by movement of the center of mass of a molecule

what is roational energy

created by the rotation of a molecule around its center of mass, spatial orientation of the body changes, center of mass remains fixed and each point in molecule is fixed relative to all other points

as activation energy increases what happens to rate constant

decreases

what is the equation for delta G and how to remember it

delta G = deltaH -Tdelta S good honey tastes sweet t is temp of the system delta h is delta h enthalpy changeo f system

what is difference between delta G and delta G not

delta G not specific value of delta G when all species have starting concentrations of one molar, uner these conditions Q=1 and RTln(Q)=0 so deltaG=deltaGnot which is what we would expect for reaction in standard conditions delta G is energy change for any given reaction under any conditions that are attainable

if only PV work is performed what is enthalpy change equation

delta H=q constant pressure, closed system at rest (because these conditions the enthalpy change is just measure of nonPV work and heat)

delta S universe equals what

delta S surrounding + delta S system

at constant temp what is equation for entropy and what type of process an you use this for

delta S= qrev/T cannot be used to find the delta S for an irreversible process between the same two states, heat q is different for an irreversible process because heat pathway dependent but entropy change will be same for any process between same two states reversible or not, delta S for irreversible process imagine a reversible process between same wo states and find heat transfer for that reversible process, since a state function the change in entropy for any process the same as change in entropy for reversible process between same two states, an since universe isolated system entropy change of universe also must be zero for any reversible reactions (in real world reversible reactions dont happen)

what is equation for delta G not under standard state

deltaG = delta Gnot +RTln(Q)

what is reaction for delta G not at equilibrium (and what parts of it vary with temp) and how does it vary against 3 cases of K

deltaGnot = -RTln(K) both K and delta G not vary with temp if K=1 delta G not=0 if K>1 then delta Gnot <0 -this does not mean that reaction always spontaneous if K greater than one, does say if reaction has K greater than one the reaction is spontaneous at the temp used to get that K and standard state if K<1 then delta Gnot>0 *all important

how to calculate delta G reaction

deltaGnot products-deltaG not reactants gives delta G not reaction (because gibbs free energy includes only state function)

what is formula for change in enthalpy

deltaH=deltaU +PdeltaV under constant pressure

delta S system +delta S surroundings=

deltaS universe (which is greater than or equal to zero)

what is change in entropy of a reaction

deltaSnot reaction=delta Snot products - delta Snot reactants (same entire thing for delta H in every variable)

if enthalpy and entropy of reaction have same sign is it spontaneous

dependso n temp (if both positive they are spontaneous at higher temp since heat transfer is required)

reaction rate

describes how quickly the concentration of reactants of products are changing over the course of the reaction, most often presented in units of molarity per second because they represent hte change in concentration of reactants and products over time

when blowing up baloon what does enthalpy equation represent

describes total energy required to blow up the balloon (fill the balloon with molecules and also work done to force atmospheric molecules apart as balloon expands)

what is a calorimeter

device that accurately measures temp change

how does solvent affect rate constant (3 ways)

dielectric of the solvent affects k, the degree of solvation also affects k, whe na reactant is dissolvedi n solvent it becomes solvated spreading out and becoming surrounded by solvent molecules, itnermolecular interactions between solvent and reactant stabilize the reactant, these solvent reactant attractions must be overcome before a reaction can take place, solvent may also stabilize reaction intermediates, also solvent viscocity affects k through cage effect (reactants in liquid get trapped in cage of solvent molecules they move around in cage at high rates making lots of collisions before squeezing between solvent molecules and into a new solvent cage, if another reactant also gets trapped in the cage many of collisions then between the reactants and a reaction will likely occur, if not another reactant in the solvent cage then teh molecule cannot react until it escapes the cage)

what is the defining feature of work vs heat

direcitonal collisiosn (heat is random collisions), cpacity to do work arises from the constrain of molecules like with piston (unconstained system like ideal gas of infinite volume can do no work)

how does rate constant relate to rate of reaction or to temp

directly proportional to rate of reaction! THUS rate of reaction increases with temp because higher temp more collisions with sufficient relative kinetic energy in givfen amount of time

what is the most important type of non PV work

electircal work

non PV work is mostly what

electrical work like muscle fibers neurons and batteries

what chemical phenomenon accountsfor electronic energy

electronic absorption/emission

what do endergonic and exergonic mean for delta G

endergonic positive delta G (non spontaneous) exergonic negative delta G (spontaneous)

anabolic reactions are usually endo or exo

endothermic

intermolecular potential energy

energy created by molecular forces between molecular dipoles

vibrational energy

energy created by the back and forth motion of atoms within a molecule

translational energy

energy created by the movement of the center of mass of a molecule

rotational energy

energy created by the rotation of a molecule around its center of mass

rest mass energy

energy described by E=mc^2

what is rest mass energy

energy described by einsteins E=mc^2

Gibbs Free Energy

energy in a system that can be used to drive chemical reactions. If the change in _____________ for a reaction is negative, the reaction will occur spontaneously.

endothermic

energy is absorbed, reaction has positive enthalpy

exothermic

energy is released, reaction with negative enthalpy

heat (q)

energy that transfers from one object to another because of a temperature difference between the objects, spontaneous transfer of energy from warmer to cooler body

what is work on molecular chemical level

energy transferred by ordered molecular collisions, net force in a direction (instead of molecules moving against eachother randomly) (compare to heat energy transfer of random collisions between high energy and low energy particles)

when is work positive or negative

energy transferred out of the system during expansion (delta E negative) energy transferred into the system during contraction (delta E positive) (BUT keep in mind they coulddefine work done by system as positive thus delta E=q-w, because technically change in heat and change in vol/work have opposite sign conventions--if given work done on system is positive use q+w, if given work done on system is negative use q-w)

alternative deinitions of reversibility

entropy undefined on scale of like two molecules reacting with eachother thus second law doesnt apply thus reactions all reversible, micromolecular systems, small numbers of molecules may have required energy at a certain time to reverse the reaction (because reactions reversible when product molecules have enough energy and orientation to go back to reagents) heating a reaction in flask increases energy in system so more collisions to shirf it to proceed, thus shifts the equilibrium constant

delta G=0 means

equilibrium

how do we denote equilibrium constant vs rate constant

equilibrium constant K rate constant k

when does Le Chatliers not apply

exceptions: solvation reaction, increased pressure due to added nonreactive gas (doesnt change partial pressures of other gasses so no change in eq)

catabolic reactions are usually endo or exo

exothermic

how do you determine order of reactants and value of rate constant for rate law

experimentation! assume no reverse reaction occurs to your given reaction, look at experimental data with concentrations and rates, see that between two changes of concentration for each reactant, look for the one that changes direclty proportional to rate changes, then look at another difference for where only the second reactant changes adn by how much compared to rate change (ie if 2x concentration but rate quadrupels then it gets exxponent of two because rate proportional to the sequare)--same thing for last reactant-- every time you do this you need to make sure other two reactants have no change, isolating change of interest and change of rate, ie if change is x4 and no rate change then the reaction rate is INDEPENDENT! of reactant so it gets 0 in rate law exponent can set it up as X^? = 4 (or whatever number times by which rate changes) same thing for Y, next reactant

if a property doubles when the systems are combined what is that property

extensive

is enthalpy intensive or extensive property

extensive, so when two identical systems combined the total enthalpy doubles

negative exxponents are equivalent to what exxponent

exxponent in the denominator

what are some examples of intensive vs extensive properties

exxtensive Volume V, moles n intensive pressure P temp T

how does presure respond with greater random translational kinetic energy of gas per volume

greater pressure

what are the only two ways to transfer energy between systems

heat (q) and work (w)

only two ways to change energy of a system are

heat and work (change in internal energy of a system at rest)

why do proteins denature at high temp

heat disrupts hydrophobic interactions and hydrogen bonds between amino acid residues that are responsible for secondary tertiary and quaternary structures

what is another word for internal energy

heat energy or thermal energy or just heat (heat energy and thermal energy are really the vibrational, rotational and translational parts of internal energy, just called thermal energy because they affect temp, heat is actually the transfer of energy this is just a dumb naming convention that mixes them)

how does temp relate to heat flow

heat flow of reaction and therefore change in enthalpy can be quantized by monitering temp change of a system coupled to the reaction

what arethe two types of catalysts and difference between them

heterogeneous or homogenous (heterogeneous is in different phase than the reactants and products like gas particles react on a solid, particles adsorb (stick to) surface of the solid with intermolecular forces) (homogenous is in the same phase as the reactants and products usually as gas or liquid, this can often be aqueous acid or base solutions)

what conditions favor kinetic vs themodynamic product

high temp drive reaction to thermodynamic, low temp favors kinetic product

what does higher emissivity mean about radiation energy

higher amount absorbed

the larger the molecule (more bonds) at a given temp what is entropy

higher entropy if larger molecule

how does entropy compare of gas vs liquid vs solid

higher for a gas than liquid which are both higher than a solid

how does temp change if greater random translational kinetic energy of gas molecules per mole

higher temp

what is a biological correlate to le chatliers

homeostasis

what does reaction order show

how changes in the reactant concentrations influence the reaction rate, order of each reactant indicates particular influence of that reactant, while order of overall reaction give more general info about realtion of reactant concentrations and rate

what does third law of thermodynamics say

hypothetical absolute zero since absolute zero, zero energy, can never be achieved, energy is eternal!

if you know three macroscopic properties of a one component system in equilibrium can you find other properties

if at least one of them is extensive then you can find all of the other properties

how can you tell if reactin is elementary from reaction order exponents and what do you do otherwise

if reaction is elementary alpha=a and beta=b ie reaction order for each reactant equal to each stoichiometric coefficient (otherwise exponents of rate law must be determined experimentally)

the entropy of a system can only decrease if what happens to surroundings

if they simultaneously increase by a greater or equal magnitude

how do we evaluate motion of molecules in a sample

impossible to know each particle, but can get average speed by manifestation of properties like pressure temp volume, motion of one individual molecuels is random and unpredictable but the sum can be useful

transition state

in a graph of reaction progress vs. energy this is the peak of the graph when activation energy has been reached; where old bonds are breaking and new bonds are forming, peak of Ea hill

what substances are at absolute entropy

in actuality it is unattainable, pure substances are just assigned entropy approaching zero as they approach 0K, think of entropy as nature trying to spread energy evenly throughout the universe

what happens to concentration differentia for direction of reaction

in direction of less concentrated side

how can you change catalyst physically to increase reaction rate

increase SA of catalyst, often by grinding it into powder

what are intensive properties

independent of the size of the system

what is difference between indergonic and exergonic

indergonic heat goes IN exergonic heat EXITS

dividng one exxtensive property by another gives what property

intensive

if two identical systems are combined and a property is the same for both the single and the combined system what is that property

intensive

is temp intensive or extensive property and why

intensive, because you dibide two extensive properties energy and number of moles

what does rate of a heterogenously catalyzed reaction depend on

intermolecular forces stick catalyst to the solid, thus depends on strength of attraction between the reactant and the catalyst, when intermolecular attractions too weak the catalyst has little effect on reaction rate, but if too strong then too much energy required to remove the reactant and the catalyst does not facilitate the reaction

what does carbonic anhydrase do as catalyst

it is enzyme essential in physiology catalyses following reaction in forward and reverse Co2+H20 = HCO3- + H+

is entropy a state function? is it intensive or extensive?

it is state function and extensive

in a closed system at rest with no electric or magnetic fields what is only type of energy change

itnernal energy

what energy does glass of water on a table have

itnernal energy and gravitational energy

what does thermal conductivity of an object depend on

its composition and to a less exxtent its temp

how does kinetic energy change with temp and how does this influence actually getting to Ea

kinetic energy increases with temp increase, thus more collisions with enough energy to overcome activation energy (proportion of collisions with energy greater than Ea will icnrease as temp increases)

how does kinetics/thermodynamic play into enolate production

kinetic/thermodynamic control can be used to produce the desired enolate from an asymmetric ketone

what is a polarized neuron

leaky because its membrane is slightly permeable to K, Na/K pumps can restore equilibrium concentrations over time

when you graph reaction order with concentration what happens

linear, slopes equal to the rate constant for given rate law, zero order y is just concentration of a reactant, first order the y is ln of that concenetration

how do number of collisions compare for gas vs liquid

liquid molecules have tons more per second because liquid moelcules in much closer proxximity to eachother, however most of the collisions in a liquid are with its solvent rather than with reactant and thus do not lead to a reaction

when catalyst concentration is large compared to reactants and products hwo does rate change with catalyst concentration

little or not at all rate change

Law of Mass Action

mathematical relationship between a chemical equation and the associated equilibrium constant, K is unitless because all concentrations are approximations

what is catalyst effect of Ez or steric factor p and what is effect

may do both or either (lower Ea thus more collisions have sufficient kinetic energy to result in a reaction which leads to more reactions and increase overall rate OR increase p which increases number of favorable collisions)

activation energy

minimum energy colliding particles must have in order to react. on a graph means that in both directions forward and reverse you must go up first regardless if moving dow or up energy gradient

how does body maintain temp homeostasis on cellular level

mitochondria can insert channels in their inner membrane that disipate the proton gradient, energy that could have been used to drive chemiosmotic coupling instead lost as heat

how does solid vibration change with temp increase

molecules in a solid vibrate faster

what is thermal energy

motion of molecules can be either translational rotational vibrational, overall sum to molecular motion called thermal energy

how do q and k relate over course of reaction

moving towards equilibrium from only reactants Q<K at equilibrium Q=K all products moving back to equilibrium Q>K

The universal entropy change for any reversible reaction must be what and why

must be zero in both directions since entropy of an isolated system cannot decrease

entropy (S)

natures tendency to create the most probable arrangement that can occur; natures tendency toward disorder (ie not going to be ordered all red beads in one and all blue beads in another randomly, its a statistical thing that unless you put in work you dont get this kind of order) can think of it like work, tendency to spread energy evenly between systems, tends to decrease energy of a system when its energy is high relative to its surroundings and to increase the energy the low compared to nearby surroundings (warm object loses energy to surroundings in a cold room, not net gained or loss in the universe just spread out, thus it is ENTROPY not energy that drives reactions in a given direction, according to second law entropy of universe is driving force of if reaction happens or not, must always increase entropy of the universe to proceed even if it itself is unfavorable to the system

if a system loses energy what is delta E

negative

is work done by a system usually positive or negative

negative because energy is lost to the environment, but you could define it as positive then w=PdeltaV is fair too!

what does second law of thermodynamics say

net entropy or disorder of the universe is always increasing, cant go back to original level or order ALSO says cant break even because temp and pressure flow downhill from greater to less, appleis to fluid and heat problems assigns a zero entropy value to any pure element or compound in its solid form at absolute zero and in internal equilibrium, at absolute zero the atoms have little motion, absolute zero temp is unattainable so the third law can be realized only theoretically

if reaction has positive enthalpy negative entropy is it spontaneous

never

does equilibrium constant change in a given reaction? when could it change?

never changes unless temp changes

do atoms in monatomic gas have rotational energy

no

does final equilibrium mix depend on amount of reactants or products you start with

no

will catalyst affect equilibrium concentrations of product and reactant

no

what are enthalpy values for a compound

no absolute values, all about the change, so scientists assign values to compounds based on standard states

can you use solids liquids gases in law of mass action

no dont use solids or pure liquids like water because their concentrations do not change over the course of the reacitons, the amounts may change but their concentraitons do not because products/reactants

is temperature heat

no heat is a type of energy transfer

zero point entropy is this a relative scale

no it is an absolute scale based on scale of relative common chemical reactions

how do you distinguish if reaction is elementary by chemical equation

no way to know!! has to state explicitly that it is elementary

can catalyst alter equilibrium constant

no!

does internal energy include bond enthalpy

no!

if volume remains constant, is PV work done

no!

do thermodynamics and kinetics have effect on each other

no! activation energy is function of kinetics enthalpy change or change in energy between products reactants is thermodynamics

bond breaking/bond forming requires what energy and for what bonds does this alter

no! always bond breaking requires energy and bond formation always releases energy true of ALL bonds also true for intermolecular and intramolecular bonds

does Ea affeect change in energy between products and reactants and why

no! because enthalpy is a state function and products/reactants determine relative enthalpy differents so doesnt matter what they overcame for final energy change

does catalyst affect kinetics and thermodynamics of the reaction

no! jjust kinetics

because line decreases on rate order graph does the rate constant decrease over time

no! rate constant is the constant slope

does path matter to product in state functions

no! state functions are pathway INDEPENDENT, just describe the state of a system (as opposed to properties that depend on the pathway used to achieve that state, path functions like work and heat, not state functions)

does standard conditions specify temp

no! you can have standard conditions at any temp (but usually assumed at 298K)

is endothermic/exothermic same as spontaneous/nonspont

no!!! dont confuse these either endo/exxo can be spontaneous or non spontaneous depending on other factors

is enthalpy conserved

no, enthalpy of universe is NOT constant

does order in which objects place matter for conduction

no, for instance cold blanket under warm blanket the same as other way around

can rate equation be used for any instant t of the equation

no, it is average over time period T

when two identical systems are combined does temp change

no, it is intensive, thermal energy doubles but so does total moles so energy per moles same

does a catalyst change equilibrium ratio of products and reactants/ how does it change equilibrium

no, just gets reaction to equilibriujm more quickly

does catalyst change overall change in energy between products and reactants

no, just overall rate not overall energy change of delta H G or S

can you apply thermodynamic functions to individual molecules

no, only for large numbers of molecules, if asked about indiivudal collisions have to use physics

do you need to know kinetics of reactions not in gases

no, only testing kinetics of reactions occurring in gases or ideally dilute solutions with cosntant temp

do atoms in a monatomic gas have vibrational energy and why

no, since they have no covalent bonds around which to vibrate

does pressure have to be constant for PV work to take place in gas against a force

no, this takes place whether or not the pressure is constant

what is turnover number

number of reactions occuring at a single active site on one enzyme per second, determines speed of action of enzyme

second and third order reactions what is reactio nrate proportional to

one case wehre rate is proportional to a single reactants concentration raised to the second or third power, other varietgy where reaction rate prportional to teh product of the concentrations of multiple reactants

what is object with emissivity of 1

only theoretically possible, absorb 100% of incident radiation so appear black

what are the three categories of systems and what defines them

open closed isolated (defined by mass and energy exchange with the surroundings)

adding two elementary steps of reaction yields what

original equation, must add to give the overall reaction

state

physical condition of a system as described by a specific set of thermodynamic properties, macroscopic state of any one component fluid system in equilibrium can be described completely by just three properties, at least one of which must be extensive, all other properties can be derived from these three (ie if pressure temp and volume are known for a one component gas in equilibrium all other properties are known like number moles delta G internal energy etc becausem sut each have specific value) can all be known without knowing how we got to a certain state

what is difference between physics work and chemistry work

physics work defined as energy transfer due to a force, work done whenever force applied over a distance which changes an objects kinetic and or potential energy, chemical system though at rest performs PV work by changing its size or shape using energy from the system, molecules comprising the system must do work to change the volume of the container, chemical system will not perform PV work spontaneously, rather outside stress initiates it like outside heat on baloon causing its gas to expand to do work on its surroundings or something

if a reaction increases the number of gaseous molecules that reaction has what entropy positive or negative

positive! for system, but not necessarily for universe, this is because gas particles more free so they can spread their energy more freely, greater the temp the greater its entropy

what is electronic energy

potential electircal energy created by the attractions between electrons and their nuclei, in a chemical reaction, changing electronic energy accounts for the greatest change in internal energy, if no chemical reaction occurs, electronic energy remains nearly constant

the value of rate constant is affected by what three things

pressure (especially for gases), presence of catalysts (lower Ea and increase rate constant) and temp (constant increases with increase temp, becuase temp is proxy for kinetic energy with more collisions to overcome0

are pressure and volume intensive or extensive

pressure intensive volume extensive

what is autocatalysis and an example of it

product of the reaction acts as catalyst for the reaction, ie acid catalyzed hydrolysis of an ester where carboxylic acid product acts as a catalyst of the reaction

equilibrium constant (K)

products to coefficients/reactants to coefficients, allows you to determine relative amount of eqch species K also - products^coefficients/reactants^coefficients

intensive property

properties independent of the size of the system

extensive property

properties that are proportional to the size of the system, DEPEND ON QUANTITY OF SUBSTANCE PRESENT

state functions

properties that describe the current state of a system, thermodynamic state functions are macroscopic properties of a system, ie can be described on an observable scale, ie for any state function the property itself sufficiently describes the nature of the system, change in a state property from oen state to another is the same regardless of process used to change it

what are extensive properties

proportional to the size of the system

what is enthalpy value of pure elements and why

pure elements in natural state at 25C are assigned 0kJ/mol as enthalpy because they are in their most stable forms

what is distinct feature of radiation compared to conduction/convection

radiation does not require a medium, electromagnetic waves can go through vacuums, like sun radiating thermal energy to Earth through space

in an overall zero order reaction what is reaction rate dependent on and explain case when this would happen

rate is independent of concentration of any reactant, occurs in enzyme catalyzed reactiosn when the concentration of substrate far outweights that of enzyme, all enzyme catalystic sites get saturated with substrate and the addition of more substrate has no effect on reacftion rate

the order with respect to any reactant is what in the rate law

reactants exponent

what to use to figure out the direction in which reaction will proceed

reaction quotient Q, since reactions go to equilibrium Q always becomes closer to K so you can always compare them if K=Q reaction at equilibrium Q>K reaction shifts left (because increasing reactants reverse reaction rate greater than forward rate, too many products compared to product reactant ratio at equilibrium) Q<K shifts right (forward reaction rate greater because too few products compared to ratio at equilibrium)

what is an elementary reaction and what is unique about it

reaction that occurs in a single step, stoichiometric coefficients of an elementary equation give the molecularity of the reactino which is the number of molecules that need to collide at one time for a reaction to occur, for example if the product coefficient is 1 and the reaction coefficient is 1 the rate at which used up is same at which produced

K = Q

relationship between Q and K at equilibrium

K > Q

relationship between Q and K favors products

K < Q

relationship between Q and K favors reactants

temperature

represents the amount of molecular movement in a substance, any increase in thermal energy increases temp--can be thought of as thermal energy per mole of molecules! think of it as how fast the molecules are moving or vibrating, when things get hot its because molecules move faster

pressure is proportional to what energy and exxplain molecular basis behind this pressure from molecules

rnadom kinetic eenrgy of a gorup of molecules per volume occupied, because pressure from molecules pushing against walls, strike walls with force that causes container to stretch until equilibrium reached by opposing force (a balancing exxternal pressure or an elastic restoring force from the container material as it resists being stretched) stretching causes container to adopt a fixxed volume

reaction quotient (Q)

same formula as equilibrium constant but for a different point in time during a reaction

how do catalyst concentrations change between start andend of reaction

same! because not altered or consumed

system

section of the universe under study

what happens to pressure differential for direction of reaction

see which side has more moles of gas, if pressure increases, the eq shifts away from that side, if pressure decreases the eq shifts toward that side

how does solvation reaction change with temp

solubility of salt increases with increasing temp even when reaction exothermic due to significant entropy increase that occurs with dissolution, entropy becomes more significant factor with higher temp (this goes against Le Chatliers though as do all solvation reactions)

the rate constant in a liquid is a function of what two things and why do these things matter

solvent and the temperature (solvents can electrically insulate reactants reducing the electrostatic forces between them)

intermediate

species that are products of one step and reactants in a later step in a multistep reaction, becuase they get used up before the end of the reaction they are not shown in overall equation, often presesnt in only low concentrations

negative delta G mean

spontaneous

entropy is

spreading out of energy

what is difference between delta H and standard enthalpies of formation

standard enthalpies of formation is deltaH not, under certain conditions

what is difference between standard state and STP

standard state-- pressure of 1 bar (about 1 atm), temp could be 25C but does NOT have to be figure out under these conditions is it gas liquid or solid and use this as reference form

First Law of Thermodynamics

states that the total energy of the system and surroundings is always conserved, any energy change to a system must equal the sum of heat flow into the system and work done on the system

Le Chatelier's Principle

states that when a system at equilibrium is stresses the system will shift in a direction that will reduce that stress

how can you physically manipulate liquids to change reactin rate

stirring or shaking may greatly increase number of collisions and thus reaction rate, also increasing temp of liquid inreases kinetic energy of particles and thus rate

what is kinetics

study of reaction rates and mechanisms, can predict rate of chemical reaction HOW FAST

catalyst

substance that increases the rate of a reaction without being consumed or permanently altered, lowers the activation energy and thereby increases the rate of both forward and reverse reactions,

what energies do you sum to get internal energy

sum of kinetic and potential energy within a system (vibrational rotational and translational are types of kinetic, while electronic intermolecular and rest mass energy are types of potential energy)

the order of the overall reaction is what in the rate law

sum of the exponents (first order reaction has only one reactant raised to the power of one in the rate law)

reaction order

sum of the exponents in a rate law, where each exponent provides the reaction order with respect to its reactant alpha plus beta is overall order of the reaction, they are related to the number of molecules that must collide for a particular elementary reaction

thermal energy

sum of the translational, rotational, and vibrational energies which together describe the overall energy of a molecule

delta G delta H delta S refer to changes in system or surroundings

system (but because H and S system depend on surroundings they are somewhat incorporated)

what three things about substances can affect rate of a reaction

temp, pressure, concentration (ie rate of reaction increases with higher temp, pressure effect though small and usually ignored)

entropy increases with what three things

temp, volume, #

for an ideal gas, enthalpy and internal energy depend on what

temperature ONLY

teh greater the thermal energy per mole the greater the...

temperature!

what does zeroth law of thermodynamics state

that temp exists, called zeroith because first second third all already discovered but all dependent on temp temperature, the state of motion of molecules exists and that temp can equilibrate

the negatibe of teh Gibbs free energy is what

the amount of non PV work in a completely reversible process (which is not actually possible so amount of non pV work actually we get out of a system is less than -deltaG magnitude

standard enthalpy of formation

the change in enthalpy for a reaction that creates only one mole of that compound form its raw elements in their standard states standard enthalpy of formation for common reactions are listed in textbooks

what is difference between stoichiometric coefficient and rate law exponent?

the coefficient tells you how many moles of A are involved in the mechanism but NOTHING about rate, must see reactants influence on reaction rate by exxperiment

internal energy

the collective energy of molecules measured on a microscopic scale; includes vibrational, rotational, translational, electronic, intermolecular potential, and rest mass energies aka includes all possible forms of energy within a system, not counting the motion or position of the system as a whole, does not include macroscopic mechanical energies such as the kinetic energy of the entire system moving as one unit or the potential energy of the entire system raised off the ground

in a first order reaction the reaction rate directly proportional to what

the concentration of a single reactant

chemical equilibrium

the condition where the rate of the forward reaction is equal to the rate of the reverse reaction, at equilibrium there is no net change in concentration of products or reactants, the point of greatest entropy!

what is enthalpy (and equation)

the energy associated with the formation of intramolecular chemical bonds, can think of it like heat H=U+ PV where u internal energy, enthalpy in joules

the system and surroundings together make up what

the entire universe

the sum of the entropy changes of any system and its surroundings equals what

the entropy change of the universe which must be equal to or greater than zero

Second Law of Thermodynamics

the entropy of an isolated system will never decrease; entropy is always increasing

how does activation energy influence reaction speed

the lower the activation energy the faster the reaction

gibbs energy change is negative of

the max amount of energy available to do nonPV work like electrical work in a cell

the more adsorption that occurs with heterogenous catalyst, how does this change the reaction rate

the more adsorption the greater the reaction rate

what would be lowest possible temp

the point at which there is no molecular motion

electronic energy

the potential energy created by the attractions between electrons and their nuclei

Arrhenius equation

the product of the collision frequency (z), the fraction of collisions having the spastion orentation (p claled stericfactor), and the fraction of collisions having the suffiencet relative energy (e^-Ea/RT) gives the rate constant (k) of a reaction k=zpe^(-Ea/RT)

at constant pressure the magnitude of PV work is equal to what

the product of the pressure and the change in volume (PdeltaV)

reactants in a liquid collide at a rate approximately equal to what

the rate of collisions between reactants in a gas with equal concentrations

rate determining step

the slowest step in a reaction mechanism; steps after the slow step do not contribute to the rate law, if another step is the slow step it is still the rate determining step but steps prior also constributge to rate law, if first step is slow step the rate law derived from just this step

what is thermodynamics

the study of energy transfer and change, can be used to predict how much eneergy a given process requires GOING WHERE, about the energy differential between reactant and product, the study of energy and its relationship to macroscopic properties, based on probabilities so only valid for systems composed of a large number of molecules (not for single collision phenomenon), whether or not a reaction will occur spontaneously but does NOT address speed, governed by delta G, greater magnitude delta G the more energyetically favorable THINK BOTTOM OF CATALYST DIAGRAM, diff between products reactants energies (as opposed to kinetics all! about! Ea!)

kinetics

the study of reaction rates, or how rapidly reaction happens and the factors which increase or decrease this speed, often provides insight into mechanism of the reaction at molecular level, does not address whether or not it will happen spontaneously, governed by activation energy, lower Ea teh more quickly it will occur

Hess's Law of Heat Summation

the sum of the enthalpy changes for each step in a reaction is equal to the total enthalpy change in a reaction regardless of the path chosen, indicates that a forward reaction has exactly the opposite change in enthalpy as the reverse (just opposite signs)

temp is

thermal energy per mole

pressure is

thermal energy per volume

radiation

thermal energy transfer via electromagnetic waves, all objects above 0K radiate heat

convection

thermal energy transfer via fluid (liquid or gas) movements, differences in pressure or density drive warm fluid in direction of cooler fluid, ie air above land heats up faster than air above water, air above land warms becomes less dense and rises and cool ocean air fills in under it

conduction

thermal energy transfer via molecular collisions, requires direct physical contact, higher energy of one system transfer some of their energy to lower energy molecules of the other system via collisions, heat can also be conducted through a single object, the ability to conduct heat is called thermal conductivity k

according to zeroth law, two bodies in thermal equilibrium share what

thermal equilibrium, a thermodynqmic property, temp, a state funciton

what is difference between kinetic and thermodynamic product

thermodynamic product more stable but requires a higher energy input and is produced more slowly, kinetic one is less stable but more rapid formation because required energy input lower

when activation energy is lowerred how does this influence thermodynamicpotential for reaction

thermodynamics compares the energy of the reactants to the energy of the products and when activation energy lowered a greater proportion of the molecules possess the energy needed to react

what is difference between enzyme and catalyst

they are jjust protein catalysts, often far more efective than ones in a lab due to specificity

when two bodies at different temp in thermal contact on macroscopic level what happens to temp

they become equal, somewhere between original temps (zeroth law)

how does heat transfer occur on a molecular level

through random collisions between molecules of two systems, in each collision energy is transferred from the higher energy molecule to the lower one, which since temp only based on the average kinetic energy of molecules in a system there is no guarantee that the higher energy molecule in a collision will be from the warmer system, but it is much more likely so the majjority of energy transfers from higher temp to lwoer temp, over time heated period becomes cooler, eventually the two bodies reach an equilibrium in which they have the same temp and kinetic energyr

what is the difference between a transition state and an intermediate

transition state for a fleeting moment, intermediate exists for longer, can be isolated and is at lower temp than transition state, intermediate would show multiple troughs among peaks on reaction coordinate graph

for monatomic gases, what is sole contributor of kinetic energy

translational energy

the temp of a gas or liquid directly proportional to what type of energy

translational kinetic energy of its molecules

when does gas molecule alter trajectory

travels randomly until collides with another partical or its container

zeroth Law

two systems in thermal equilibrium with a third system are in thermal equilibrium with each other

what are three most common molecularities and what do they mean

unimolecular, bimolecular, termolecular, if both reactant coefficients equal to one then bi molecular

surroundings

universe outside of the system, assignment is arbitrary depending on what you want to measure in your system

how to know exponent for rate law in elementary step/equation

use coefficient!

in exxperiments how does concentration of catalyst usually compare to concentrations of the reactants and products

usually small relative to the concentrations of the reactants and products

in equilibrium expression how do we express concentration of pure liquid or pure solid

value of one so it does not contribute to value of equilibrium constant, even though solves not actually pure they are usually considered idelaly dilute which means they hve mole fraction of one, pure solids or liquids can still participate in the equilibrium just not the constant so you cant get rid of them

what energy in internal energy is responsible for denaturation

vibrational energy , as atoms vibrate with increasing energy about their covalent bonds they acquire the energy needed to overcome energetic barriers imposed by intermolecular forces, loss of 3d shape results in loss of protein function

how to calculate work done under constant pressure

w= - P delta V (because if force constant pressure also constant)

when can you use rate expression to approxximate non elemental reactions

when concentrations of intermediates are low

under what circumstances does a reaction run to completion

when forward reaction just so much more favorable or if you remove the products like a gas

what happens to temp differential for direction of reaction

write heat as a reagent or a product, if heat taken out, the eq shifts toward side of the equation with the heat, if heat added, the eq shifts away from the side of the eq with heat

what are axis on reaction curves with Ea

x is reaction progress, y is energy gibbs free energy or enthalpy

are molecules always in motion

yes

do all physical properties change when temp changes

yes

is internal energy a state function

yes

is the universe an isolated system

yes

is work a path function

yes

is gibbs free energy extensive is it a state function

yes and yes (like enthalpy it is not conserved) ie gibbs free energy of an isolated system can change, which makes sense because it is a function of enthalpy and entropy, which are not conserved

is enthalpy a state function

yes because U P and V to make it are state functions, thus doesnt matter what reaction takes place just look at initial and final

does entropy increase with more of the substance

yes because it is extensive (and size volume and temp)

will there always be some amount of each species present at equilibrium

yes for a homogenous reaction (all products reactants in same phase)

do molecules have to collid for chemical reaction to happen and how does this link rate of given reaction and frequency of collisions

yes must collide for reaction but rate of given reaction usually lower than frequency of collisions because there are two requirements for given collision to initiate reaction

do higher temps increase both direction rates of reaction

yes!

does enthalpy change with temp?

yes! increases with temp!!

does the rate of reaction increase with temp? does it change equilibrium? why

yes! kinetics and themodynamics separate so increasing rate does not tell you about equilibrium it just means equilibrium achieved more quickly

when two bodies at equilibrium do collisions still occurt

yes, and have have same temp and kinetic energy but there is no net transfer of energy between the two bodies because the higher energy molecule is jsut as likely to originate form the first system as from the second

is enthalpy equal to heat

yes, assuming constant pressure reaction, thus exothermic is heat flow to surroundings while endothermic is heat flow to teh system

do macroscopic phenomena correlate with molecular phenomena/atomic behavior? which ones correlate to which

yes, observable properties are a product of this, ie temp correlates with molecular motion, pressure with molecular forces, volume with molecule bonding

does catalyst create new reaction pathway

yes, often includes intermediate too, creates alternative reaction mechanism that competes with uncatalyzed mechanism , new energy pathway which increases both rate of forward/reverse

are oygen molecuels in air moving

yes, very quickly, but we dont feel because not much mass

can increasing catalyst concentration increase the rate of the reaction

yes, when this happens the concentration of the catalyst will be foundi n the rate law

how could you calculate k with rate law

you can plug in data from any single trial into the rate law once you have determined correct rate law/exponents

if a reactant doesnt appear in the rate law what is the xponent

zero (because reaction rate doesnt depend on that reactant)

entropy change for a reversible reaction is what

zero, because must have same enetropy as it did before the reaction took place if you return with entropy as state function

units for entropy are what

J/K

what is difference between k and q

K equilibrium constant gives standard themodynamic favorability of a reaction in its stable equilibrium state, fixed for that reaction at a certain temp Q reaction quotient gives snapshot of reaction at point in time, compared to K tells direction in which must shift for equilibrium

what is average kinetic energy of a single molecule in any fluid

KE avg per molecule = 3/2kT (k is Boltzmanns constant), average of three modes of kinetic energy each averaging 1/2kT

what is average translational kinetic energy for a mole of molecules in any fluid

KEavg per mole molecules = 3/2 RT where R is idela gas constant

are reactants and products concentrations equal at equilibrium

NO the concentrations are not changing, but they are not the same as eachother

can you solve for equilibrium constant under non equilibrium conditions

NO! plugging in concentrations of products and reactants will not give you equilibrium constant unless youre at equilibrium (instead use q)

can you always assume you can use coefficients of the balanced equation in a rate law

NO!! Only if you know reaction is elementary

what can you assume about rate equation without knowing the reaction is elementary

NOTHING, need more info other than just equation

is internal energy of ideal gas expressed as function of temp and volume

No! for any ideal gas any state function can be exxpressed as a function of temp and volume, but the internal temp of ideal gas is independent of volume (only pressure dependent)

equilibrium achievfed when

POINT OF MAX UNIVERSAL ENTROPY when rate of the forward reaction equals rate of reverse reaction, point of greatest universal entropy, and reaction has reached equilibrium when has achieved the max universal entropy for that reaction

what are two types of work in a chemical system

PV work and non PV work

what is formula for reaction quotient

Q givne by formula identical to equilibrium exxpression except reaction not at quilibrium Q may have any positive value Q=products^coefficients/reactants^coefficients

which ideal gas constant should you use with kinetic energy equations

R=8.314 j *atm/molK because it includes an energy unit unlike the other version!

do C and K have signs

C yes, K does not because Celcius is relative but Kelvin is actual thermal energy, thus it is incorrect to say 12.5 C is half as hot as 25 C, but it is true that 12.5 K is half as hot as 25K because has half as much thermal energy

ln1=

0

at equilibrium what is della G and why

0 ecause there is no available free energy to do work with at equilibrium

what are the thermodynamics laws

0-two bodies in thermal eq with same system are in thermal eq with eachother, ie temp exists and is state fxn 1-energy of isolated system conserved for any rxn 2-entropy of isolated system never decreases 3-perfect crystal at zero K assigned an entropy value of zero, all other substances at all other temps have positive entropy (0K unattainable)

how does rate constant compare with rate of the reaction

DONT CONFUSE! Proportional but NOT identical

Kelvin

SI unit of temperature = degrees C+ 273 0 K is absolute zero increase of 1C is equivalent to 1K increase, just atart at different points C also tested