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216 Cards in this Set
- Front
- Back
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Question
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Answer
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a spontaneous react may or may not?
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proceed to completion
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system
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partic part of universe being studied
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enviroment
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everthing outside system
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system can be?
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isolated closed open
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isolated system can?
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it can not exch e or matter with surroundings
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give an ex of an isolated system?
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insulated bomb reactor
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closed system is?
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can exch e but not matter
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ex of a closed syst
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steam radiator
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open system is?
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can exch matter and e with surroundings.
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give example of an open syst?
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pot of a boiling water
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a system undergoes a ____________ when one or more of its properties change
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process
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a system undergoes a process when?
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when one or more of its prop change
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isothermal process is?
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temperat of systm is const
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adiabatic proc is when?
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no heat exch occurs
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isobaric process is?
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press of systm is const
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no heat exch occurs in a __________ process
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adiabatic
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which 2 processess are common?
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isothermal and isobaric. temp and ress are easy to contr
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T or F heat and temp are different
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t
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heat is a?
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form of energy that can leave or enter a syst
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temp is?
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a measure of average ke of particles in a systm
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____________ is a meas of the averag ke of the particles in a syst
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temperature
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heat is a form of e that transfers bec of?
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a temper diff betw syst and its surroundings
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heat absorbed by a system is?
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pos
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heat lost by a system to surrounding is?
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negative
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endothermic react?
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absorb e
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exothermic react?
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release e
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units of heat?
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joules
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1 cal = ________ J
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4.184 J
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joules and calories are units for?
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heat
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calorimetry measures?
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heat changes
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what condit are heat changed measured under?
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const vol calorimetry const press calorimetry
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heat absorbed or given off in a process is =?
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q=mc chT
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q=mc chT c is?
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specific heat
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q=mc chT q is?
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heat
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const vol calorimetry what dev do you use?
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bomb calorimeter
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bomb calorimeter no ____________ enters or leaves the system
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heat
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q react + q water + q steel=0 in a ?
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bomb calorimeter
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bomb calorimeter
the overall system is? |
adiabatic
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macroscopic prop include?
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temp T press P volume V
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state functions
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prop that dep only on initial and final states of the system
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name 7 state funct?
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temp vol enthalpy entropy free energy internal energy E and U
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H is?
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enthalpy
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s is
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entropy
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G is ?
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free energy
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E or U is?
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internal energy
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standard condition for enthalpy etc is?
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25 C
1 atm |
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standard state of a subs is the form a subst takes?
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at 25 C and 1 ATM
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standard condit in thermody must not be confused with?
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standard temperature and pressure in gas laws STP
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heat changes at const press
is |
enthalpy
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enthalpy is?
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heat changes at constant pressure
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enthalpy of a process does not depend on the?
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path
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T or F ΔHreact=Hprod-Hreact
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T
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T or F it is not poss to meas H directly
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T
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only ____________ in H can be measured
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Δ
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stand heat of format of a compound is?
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enthalpy ch that would occur if one mole of a comp were formed direct from its elem in their standard states
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ΔHf of an element in its standard state is?
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zero
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standard heat of react is?
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ΔHreact= (sum of ΔHf of prod)-(sum of ΔHf of react)
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Hess law says?
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that enthalpies of react are additive
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for hesses law
if you multiply the prod and react by 3 ( or a cert number) then what must you do to ΔH? |
also multiply it by 3
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reverse reaction has the same __________ as that of the forward react
but its ________ is oppos |
enthalpy
but its sign is oppos |
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bond e or bond dissoc e is?
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averag of the energy req to break a part type of bond in one mole of gaseous molec
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bond ____________ is always endothermic
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breakage
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bond ______________ is always exothermic
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formation
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H2 (g) ---> 2H (g) ΔH= will be?
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positive
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bond e can be used to estim the ?
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enthalpies of reactions
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ΔHreact can be estimated by?
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=(ΔH of bonds broken)- (ΔH of bonds formed)
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for simple diatomic molec such as H2
bond dissoc e can be easily measured? |
spectroscopically using react E=hv E=bond dissoc e and v is freq of light absorbed
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spectroscopy can be used to measure the bond dissoc e of?
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simple diatomic molecules
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what are the req for relatively easy measure of ΔH?
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that react be fast and spontan
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entropy is the meas of?
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disorder of a system
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what are units of entropy?
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j/K
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J/K are the units for ?
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entropy
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a solid has a lower entropy than a ?
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gas
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t or f entropy is a state function
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T
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ΔS=Sfin- Sinit
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Sfin- Sinit
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qrev/T =
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ΔS
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ΔS= ?/T
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qrev/T
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entropy qrev is ?
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the heat added to the syst undergoing a rever process.
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freezing has a ___________ in entropy
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decrease
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boiling has a ____________ in entropy
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increase
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second law of thermodyn says that?
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all spont proceed so that entropy of the systm plus its surr increases
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ΔSuniv >
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0
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a sytm reaches its maxim entropy at?
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equilibrium
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for a revers procc ΔSuniv is?
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zero
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Gibbs free energy combines what 2 fact?
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ΔH and ΔS
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Goose hunters take shotguns reminds you of?
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ΔG=ΔH-TΔS
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ΔG=?
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ΔG=ΔH-TΔS
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in the equilbr state
free e is? |
at a minimum
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ΔG <0 means a proc can?
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occur spont
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for any given nonspont react or proc
the reverse react or proc will be? |
sponaneous
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if ΔG is zero the system is?
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in a state of equil
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thermody and kinetics spontan does not necessaril mean?
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instantaneous
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ΔH ΔS Outcome ? - +
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spontaneous at all temperatures
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ΔH ΔS + -
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nonspontaneous at all temperatures
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ΔH ΔS + +
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spontaneous only at high temperatures
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ΔH ΔS - -
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spontaneous only at low temperatures
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rate of a reac depends on?
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activat e
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t or f rate of a react dep on ΔG
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f
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standard free energy ΔG is ?
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ΔG of a proc occur at 25 C and 1 atm . concentr of sol are 1 M
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standard free energy of format of a comp is?
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free energy ch that ocurs when 1 mol of a comp in its stand form
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standard free energy of format of any elem in its most stable form is?
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zero
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conversion of C (diamond) to C (graphite) is __________ but its rate is slow
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spont
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ΔG react=(sum of ΔGf of prod)- ??
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=(sum of ΔGf of prod)- (sum of =(sum of ΔGf of react)
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-RTlnKeq =
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ΔG
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what is the equat for ΔG from equil const?
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ΔG=-RTlnKeq
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once a react commences a standard state condit?
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no longer holds
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once a react commences Keq must be replac by?
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reaction quotient Q
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the react quotient Q is=
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Q=[C]^c[D]^d/[A]^a[B]^b
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when a react commences ΔG=?
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ΔG= ΔG° + RTlnQ
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discuss when water boils in terms of ch in G
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TchS> chH only when T is above 373 K
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Question
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Answer
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1st law of Thermodynamics
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Energy of the universe is constant; Energy can never be created or destroyed
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2nd law of Thermodynamics
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System spontaneously move toward disorder(high entropy)
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ΔE:?
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ΔE= q + E
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w= -pΔV
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+w = V is - -w = V is +
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Locked piston
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ΔE = q
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Unlocked piston: When heat piston
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Volume increases Work is - PE increases so ΔE decreases " Expanding gases cool"
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Unlocked piston: Put weight on piston
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Work is + Temp increases "compressed gases warm"
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Isobaric
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Pressure constant area= work done by gas
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Isochoric
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Volume constant Area= 0 so work= 0
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Isothermal
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Temp constant ΔE=0 so q=-w
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Adiabatic
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no heat transfer q=0 ΔE=w "perfectly insulated system"
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Entropy
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Amount of disorder
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Increasing entropy means:
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1) Phase change 2) Increasing # of moles of gas dissolved; the side with the more mol of gas has more entropy
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Enthalpy
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amount of heat gained or lost when bonds are formed or broken
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Bond breaking
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requires energy
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Bond forming
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releases energy
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(-)ΔH
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exothermic heat is product product have stronger bond that the reactant
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(+)ΔH
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endothermic heat is reactant reactant have stronger bonds
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Hf=0 when?
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when elements are in their natural state
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ΔG
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Gibbs free energy Energy evolved or absorbed as the rxn goes from rxn to product
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(-)ΔG
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product have less energy more stable spontaneous exergonic(energy is given off)
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(+)ΔG
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Product have more energy less stable nonspontaneous endergonic
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ΔG=0
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prod and reac have same energy rxn is @ equilibrium
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Low temperature
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ΔH dominated if ΔH and ΔS are both (-):spon
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High temperature
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ΔS dominates
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Kinetics
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rates
activation Energy catalyst temp |
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Thermodynamics
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ΔG
H S Equilibrium Temperature |
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Question
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Answer
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1st Law of Thermodynamics
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The total energy of the universe is constant
that is it cannot be created or destroyed. (You can't win.) |
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2nd Law of Thermodynamics
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Processes tend to run toward entropy. (You can't break even).
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Equation for internal energy of a system
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dE= q+w
where dE is proportional to Temp |
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Isochloric system
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A system where thre is no change in volume. dE=q because w=-PdV=0
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Work of a system
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w=-pdV when a piston moves up
there is a gain in PE system is doing work on the surroundings |
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Isobaric SYstem
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dP=0
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Isothermal System
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dT=0
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Adiabatic System
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no heat is transferred between the system and its surroundings all energy is transferred as work
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Entropy
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the measurement of things moving toward disorder
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Enthalpy
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the energy that must be put into a bond in order to break it when a bond is formed
energy is released |
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Heat of a rxn
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change in enthalpy (dH) -dH= exothermic +dH= endothermic
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Heat of a rxn for diatomic and monatomic elements in their natural state
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dH=0
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Standard state
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298K (25C)
1 atm pressure 1M |
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Hess's Law
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The sum of energies absorbed or released in all steps will be the same as that of the overall reaction.
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Rules for Applying Hess's Law
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1. If a rxn is reversed
the sign of dH is reversed 2. If an equation is multiplied by a constant dH is also multiplied by the same constant |
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Gibbs Free Energy
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dG= dH-TdS -dG= spontaneous rxn +dG= nonspontaneous rxn dg=0= equilibrium
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Spon or Nonspon? -dH +dS
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spon (-dG)
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Spon or Nonspon? +dH +dS
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spon at high temps (-dG) nonspon at low temps (+dG)
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Spon or Nonspon? -dH -dG
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nonspon at high temps (+dG) spon at low temps (-dG)
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Spon or Nonspon? +dH -dS
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Nonspon (+dG)
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t/f Catalysts are able to change dS
dH and dG |
F
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Thermodynamics and Equilibrium
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dG (standard state)= -2.3 RTlog Keq
where Keq=10^(-dG/5700)@STP -dG (standard state)= spon Keq> 1 +dG (standard state) = nonspon Keq<1 0=dG (standard state)= equil Keq=1 |
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Mass defect
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the difference in the masses of individual nucleons and their mass when combined
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what is the equation to find the energy that is made when nucleons come together
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E-mc^2 c= speed of light m = mass defect
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Question
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Answer
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138. What is an isolated system in thermodynamics?
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A system is isolated if it doesn't exchange either energy or material with its environment.
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139. What is a closed system in thermodynamics?
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A system is closed when it can exchange energy
but no material with its environment. |
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140. What is an adiabatic transition?
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The transition where no exchange of heat occurs
is called adiabatic. |
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141. What kind of quantities are called extensive?
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Additive quantities are called extensive.
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142. What is the entropy of a chemically pure
solid crystal at absolute zero temperature? |
S = 0
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143. Can entropy be negative?
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No
it cannot. |
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144. What is the entropy and temperature of a single particle with velocity v?
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It is not interpreted. Thermodynamics only deals with systems
i.e. with multitude of particles. |
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145. Is chemical potential an extensive or an intensive quantity?
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It is an intensive quantity.
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146. Two bodies are in thermodynamic equilibrium (T1=T2). Can exchange of energy occur between them?
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Yes
but the average amount of energy transmitted by the bodies to each other is equal. |
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147. What is the entropy change (ΔS) in an isolated system undergoing a reversible cycle?
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ΔS=0
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148. Is a living system an isolated
closed or open system? |
Open.
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149. Is the second law of thermodynamics valid for a living system?
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Yes
but it can be applied only if the living system and the surrounding environment is treated as an isolated system. |
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150. When is a mixture in thermodynamic equilibrium?
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If the chemical potential of all of its components is the same at each point of the system.
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151. What is the classical thermodynamic definition of entropy?
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ΔS = Qrev/T ΔS: entropy change
Qrev: heat taken up reversibily T: absolute temperature |
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152. Define the relationship between entropy and thermodynamic probability!
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S = k ln W S: entropy
k: Boltzmann constant W: thermodynamic probability |
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153. Define thermodynamic probability!
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Thermodynamic probability of a macrostate is the number of microstates associated with the macrostate.
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154. What is the range of values of thermodynamic probability (W)?
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1 ≤ W < ∞
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155. What is the range of values of mathematical probability (P)?
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0 ≤ P ≤1
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156. Which state functions determine the direction of a chemical reaction in an a.
isobaric (p=constant) and b. isochoric (V=constant) transition? Give the definition of these functions! |
a.
Gibbs-free energy G=H-TS b. Helmholtz-free energy F=E-TS where H and E are the enthalpy and the internal energy of the system respectively and T and S are the absolute temperature and the enthropy of the system respectively. |
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Question
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Answer
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rate law forward
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k[R1][R2] - det experimentally
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factors affecting rxn rate
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T
[reactant] medium catalysts (take rxn to equil but do not change equil b/c equally fast fwd and reverse rxn) |
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P
V and moles (Le Chatlier's) |
inc P or dec V = favor side w/ fewer moles gas
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Rxn orders
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sum of exponents in rate law (can have fractional
mixed order rxn) |
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K = 1
K >1 K<1 |
equal P and R
more P more R |
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enthalpy
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measure of heat change at constant pressure
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(standard) enthalpy of rxn
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sum Hprod - sum Hreact (at standard conditions - b/c Hf element = 0)
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standard heat of formation
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Hf = characteristic of compound formed from elem in standard state b/c Hf element = 0
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Hess's Law
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enthalpies of rxn are addititive (manipulate steps to get net rxn (mult coeff = mult enthalpies) + switch direc of rxn = switch sign of H)
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Bond dissociation energy related to enthalpy
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can give E of formation of compound (intermed steps); ∆Hrxn = Bonds Broken - Bonds Formed
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Entropy
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∆S = Q/T (greater entropy = greater disorder)
∆Suniv = ∆Ssystem + ∆Ssurround = > or = (if equil) 0 |
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Gibbs free E
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∆G = ∆H - T∆S
(if neg indicates max amt W can be done b/c in J) |
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heat capacity
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specific heat c * mass
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specific heat and amt heat transfer (relation)
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higher = higher per 1 degree inc
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What forms faster - more KN or TD stable product?
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KN b/c lower Ea
but if T high enough + molec has enough E will pref TD product |
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acetylene structure
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ethyne! C2H2
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enthalpy
entropy and free energy are all __ functions |
state functions - path independent
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1 atm = ___ torr/mm Hg
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760
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Ideal Gas Assumptions
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no IMF
elastic collissions molec no vol high T low P |
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Van-der-Waals eq for real gasses (actual P and V are ___)
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(P+an^2/v^2)(V-nb) = nrt ; actual P less
V more |
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Dalton's Law of Partial Pressures
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Pa = XaPt
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Kinetic Molecular Theory of Gas says
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properties of whole gas dependent on motion of individ particles
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Kinetic Molec Theory Assumptions
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no IMF
KE for all gasses same at same T elastic continuous motion particles = 0 vol |
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Avg Molec Speed
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KE = 3/2kT (k = boltman's) = for 1 particle!!
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RMS speed of a Gas
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Sq Rt (3RT/MM)
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Rate of Effusion and Diffusion equations
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Sq Rt (inverse of MM's) set up ratio of RMS + cancel numerator
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3 types of cubic unit cells (make up crystals)
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simple cube
body cube (1 more molec in middle) face-centered cube (1 more molec per side) |
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Characteristics of Ionic structures
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poor e- conduc in solid
strong IMF = immobile (metallic strucutres - strong covalent bonds) |
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Freezing pt
Boiling pt effect by solute molecs + equation (quant) |
change = Kf or Kb*m (molality) (fp goes down
bp goes up) |
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Eq for Osmotic Pressure
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P = MRT (more solute = > p b/c M = molarity)
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Raoult's Law
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VP dec as # solutes inc: Pa=Pao*Xa (solute or solvent) - only for ideal solns where attraction b/w all molecs is the same
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