AP Chemistry – Physical Chemistry

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law of mass action
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also called the equilibrium expression; law that says that the concentrations of all the products multiplied together divided by those of the reactants will be equal to the equilibrium constant K
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specific reaction, temperature of the reactants at equilibrium
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value of the equilibrium constant depends on _ _ _ _ and _ _ _ _
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K(p)
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equilibrium constant for the partial pressures of gases
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K(sp)
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equilibrium constant for solubility product
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K(f)
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equilibrium constant for formation constant of complexities
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K(d)
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equilibrium constant for dissociation constant in complexation reactions
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constant concentration, pure liquids/solids
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all substances with ___ ___, such as __ __ __, are not part of the equilibrium expression
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K(1) x K(2)
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when adding chemical reactions, K(overall) equals _ _ _
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to determine the extent to which reactants are converted into products
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purpose of equilibrium constant
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10^-10
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if K is less than ___, no visible reaction occurs
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greater than 1.00
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spontaneous reactions have equilibrium constants __ __ __
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less than 1.00
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nonspontaneous reactions have equilibrium constants __ __ __
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reaction quotient “Q”
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number obtained by entering all the required concentrations into the equilibium expressions and calculating the result (not at equilibrium)
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forward, reverse
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if QK(c), the reaction will move in the ____ direction
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K(p)=K(c) x (RT)^Δn(g)
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given equation for K(p)
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K(p)
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if the value of an equilibrium constant is given without speciying K(p) or K(c), you can assume that it is ___ the chemical equation requires one or more substances in solution
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common ion effect
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a decrease in the solubility of a compound when it is dissolved in a soution that already contains an ion in common with the salt being dissolved
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complexes
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metal ions react with anions and molecules to form this
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formation constant
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equilibrium constant when the reactants come together to form a complex ion
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dissociation constant
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equilibrium constant when the complex ions reactant breaks apart into products
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Le Chartelier’s Principle
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whenever a system in dynamic equilibrium is disrupted by changes in chemical concentrations or physical conditions, the system will respond with internal physical and chemical changes to reestablish a new equilibrium, if possible
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Δn(g) is not zero
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increasing the pressure of a gaseous reaction system by decreasing its volume will have an effect on the equilibrium only if _______________
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reactants, products
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increasing the pressure on gaseous reactants favors the ______, while decreasing favors the ______
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temperature
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the only experimental variable that has any effect on the value of the equilibrium constant is ____
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reactants
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temp increases, reaction exothermic, favors ___
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products
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temp increases, reaction endothermic, favors ___
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products
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temp decreases, reaction exothermic, favors ___
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reactants
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temp decreases, reaction endothermic, favors ___
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mol/Ls
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unit of reaction rates
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kinetic cruve
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another name for concentration vs time curve
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-ΔC/Δt
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slope = -rate(reactants) = rate(products) = this
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concetration, temperature, ability to meet (phase), catalyst present
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4 factors that affect reaction rates
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false, they never do
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T/F: catalysts always appear in the balanced equation
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rate = k * [A]^x * [B]^y * [C]^z
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rate law equation
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true
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T/F: there is no theroretical way to predict the exponents of a rate law
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exponents of the rate law
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the order of the reaction indicatesthis
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true
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T/F: you can be first order in respect to one reactant and second order overall
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(mol/Ls) / (mol/L)^order
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unit of the rate constant of the rate law
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ln(k) = -E(a)/RT + ln(A) where E(a) is activation energy, R=8.314J/(mol*K), temp is in K, A is the proportionality constant
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Arrhenius equation; one way is k = A*e^(-E(a)/RT)
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1/T, ln(k), -E(a)/R
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Arrhenius plot has the x axis ___, the y axis __ and the slope ___
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-E(a)/R * ( 1/T(1) – 1/T(2) )
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to compare two rates, ln( rate(1)/rate(2) )
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larger rate will always be the higher temp, activation energy is always positive
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two principles to check the reasonableness of Arrhenius equation-generated answers
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does not depend on the concentration of any reactant, [A], -k, [A] = [A(0)] – kt, [A(0)] / 2k
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zero order reaction means rate _ _ _ _ _, y axis of a _ _, a slope of _, an integrated rate equation of _ _, and half-life of _ _
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ln[A(0)], -k, ln( [A(0)]/[A] ), 0.693/k
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first order reaction has y axis of a _ _, a slope of _, an integrated rate equation of _ _, and half-life of _ _
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1/[A], k, 1/[A] – 1/[A(0)] = kt, 1/k[A(0)]
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second order for [A(0)]^2 has axis of a _ _, a slope of _, an integrated rate equation of _ _, and half-life of _ _
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collision theory
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reaction rate is equal to the frequency of the effective collisions between reactants
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molecules collide with sufficient energy and in proper orientation so products form
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for collisions to be effective, _ _ _ _ _
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kinetic molecular theory (of gases)
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fraction of all collisions that have the miniumum energy needed for reactions can be calculated using _ _ _
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N*f(e)*f(o) = (number of collisions per sec)(fraction with minimum energy)(fraction with correct orientation)
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reaction rate using collision theory
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temperature, concentration of reactants
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number of collisions per sec depends on _ and _
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fasle, just f(e)
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T/F: f(e) and f(o) both increase as temp increases
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transition-state theory
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describes the molecular configurations and energies as a collisions occur, recognizing that proximity distorts molecules, weakening bonds within molecules so they break and new ones form
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activated complex
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state represented in this ex: as Cl and HI approach, H-I bond weakens and H-Cl bond strengthens until the former is half broken and the latter half formed (upon recoiling the state breaks apart)
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reaction profile
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also called potential energy diagram, it shows the energies of reactants during collisions
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potential energy (as KE decreases, PE increases), reaction coordinate (location?)
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reaction profile has a y axis of _ _ _ and an x axis of _ _ _ (helps detemine heat of reaction and E(a) of reverse reactions)
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inversely
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rate constant is _ related to activation energy
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reaction mechanism
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complete sequence of steps in a reaction
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elementary reactions
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series of smaller steps in a reaction usually involving one molecule breaking apart or two reactants colliding
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coefficients in the balanced equation
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in elementary reactions, the exponents of the rate law are _ _ _ _
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rate-determining step
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also called the rate-limiting step, this is the slowest state that determines the overall rate of the reaction
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imtermediate
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any chemical species that is part of a mechanism but not part of the balanced equation
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steady-state assumpion
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if the second state is the rate-determining step, the first reaction must be relatively fast and reversible, meaning the formation of the intermediate is equal to its disappearance and the forward rate in the orginial rate equation equals the reverse rate of this intermediate reactant (PR pg 414)
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isolated system
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where there is no transfer of energy or matter to or from the surroundings
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closed system
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where energy can be transfered to the surrounds but matter cannot
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state functions
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describe an aspect of a chemical system (like pressure, temp, volume, number of atoms/molecules) and depend on the change in a function, not initial numbers (ex: 15 to 4 = 125 to 114)
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heat (q), work (w)
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two non-state functions are _ and _ as they depend on the sequence of events used to transform matter from the initial state ot the final state
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extensive
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___ properties are qualities that change as the amount of the sample changes
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extensive
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internal energy, enthalpy, entrophy, Gibbs free energy are all ___ properties
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temp, pressure, mass, physical state
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to make extensive properties intensive, we must define precisely _, _, _, and _ _
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lost, gained
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exo- means energy _; endo- means energy _
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.5mv^2
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equation for KE
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m(1)m(2)/r, q(1)q(2)/r
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gravitation energy (PE) has an equation of _ while electrostatic attraction (PE) is _
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specific heat
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energy needed to raise 1 gram of a substance 1 degree C
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1 cal/gC or 4.184 J/gC
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specific heat of water
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Dulong and Petit Law
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specific heat x molar mass is about equal to 25/molC
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ΔE = q + t
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first law of thermodynamics can define energy using the equation
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force x distance = pressure x area x distance = pressure x Δvolume
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equation for work
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heat with constant pressure
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q(p) meaning
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heat with constant volume
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q(v) meaning
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bomb calorimeter
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calorimeter that does not allow volume to change, making ΔE zero
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enthalpy
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H; heat content of a substance
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ΔE = ΔH -PΔV
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relationship between energy and enthalpy
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standard heat of a reaction, kJ
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meaning of ΔH°, which has units of _
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standard heat of formation, kJ/mol
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meaning of ΔH(f)°, which has units of _
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Hess’ law
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whenever mathematical operations are performed on a chemical equation, the same mathematical operations are applied also to the heat of reaction (like multiplying by constants or adding equations)
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reactants are elements in their standard states at 25C and 1 atm, and there is 1 mole of product
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requirements of a formation reaction
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entropy
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related to the number of different wars in which a system can arrange the particles within it
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S, JC, JC/mol
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entropy has a symbol of _ and units of _ while standard entropy has units of _
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false, this does not apply to S°
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T/F: for elements, the standard heat of formation, standard entropy values and standard free energy are all zero
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S = k*ln(w) where k is the Boltzmann constant and w is the number of microstates
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Boltzmann entropy equation
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S°=q(rev)/T
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equation for standard entropy
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reversible process
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process that occurs in infinitesimally small steps from initial to final state
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true
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T/F: the greater the position value of Δn(g), the greater the entropy
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free-energy change
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ΔG°; maximum amount of energy available from any chemical reaction
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ΔG° = ΔH° – TΔS°
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equation for Gibb’s free energy
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negative
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if ΔG° is ____, the reaction is always spontaneous
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ΔG = ΔG° + R*T*ln(Q)
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equation for Gibb’s free energy not in standard state
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ΔG° = -R*T*ln(K)
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equation for Gibb’s free energy in standard state
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PR pg 442
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diagram for ΔG°

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