mcat chemistry chapter 6 thermochemistry kaplan
Terms
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- a spontaneous react may or may not?
- proceed to completion
- system
- partic part of universe being studied
- enviroment
- everthing outside system
- system can be?
-
isolated
closed
open - isolated system can?
- it can not exch e or matter with surroundings
- give an ex of an isolated system?
- insulated bomb reactor
- closed system is?
- can exch e but not matter
- ex of a closed syst
- steam radiator
- open system is?
- can exch matter and e with surroundings.
- give example of an open syst?
- pot of a boiling water
- a system undergoes a ____________ when one or more of its properties change
- process
- a system undergoes a process when?
- when one or more of its prop change
- isothermal process is?
- temperat of systm is const
- adiabatic proc is when?
- no heat exch occurs
- isobaric process is?
- press of systm is const
- no heat exch occurs in a __________ process
- adiabatic
- which 2 processess are common?
- isothermal and isobaric. temp and ress are easy to contr
-
T or F
heat and temp are different - t
- heat is a?
- form of energy that can leave or enter a syst
- temp is?
- a measure of average ke of particles in a systm
- ____________ is a meas of the averag ke of the particles in a syst
- temperature
- heat is a form of e that transfers bec of?
- a temper diff betw syst and its surroundings
- heat absorbed by a system is?
- pos
- heat lost by a system to surrounding is?
- negative
- endothermic react?
- absorb e
- exothermic react?
- release e
- units of heat?
- joules
- 1 cal = ________ J
- 4.184 J
- joules and calories are units for?
- heat
- calorimetry measures?
- heat changes
- what condit are heat changed measured under?
-
const vol calorimetry
const press calorimetry - heat absorbed or given off in a process is =?
- q=mc chT
-
q=mc chT
c is? - specific heat
-
q=mc chT
q is? - heat
-
const vol calorimetry
what dev do you use? - bomb calorimeter
-
bomb calorimeter
no ____________ enters or leaves the system - heat
- q react + q water + q steel=0 in a ?
- bomb calorimeter
- bomb calorimeter, the overall system is?
- adiabatic
- macroscopic prop include?
-
temp T
press P
volume V - state functions
- prop that dep only on initial and final states of the system
- name 7 state funct?
-
temp
vol
enthalpy
entropy
free energy
internal energy E and U - H is?
- enthalpy
- s is
- entropy
- G is ?
- free energy
- E or U is?
- internal energy
- standard condition for enthalpy etc is?
- 25 C, 1 atm
- standard state of a subs is the form a subst takes?
- at 25 C and 1 ATM
- standard condit in thermody must not be confused with?
- standard temperature and pressure in gas laws STP
- heat changes at const press, is
- enthalpy
- enthalpy is?
- heat changes at constant pressure
- enthalpy of a process does not depend on the?
- path
-
T or F
ΔHreact=Hprod-Hreact - T
-
T or F
it is not poss to meas H directly - T
- only ____________ in H can be measured
- Δ
- stand heat of format of a compound is?
- enthalpy ch that would occur if one mole of a comp were formed direct from its elem in their standard states
- ΔHf of an element in its standard state is?
- zero
- standard heat of react is?
- ΔHreact= (sum of ΔHf of prod)-(sum of ΔHf of react)
- Hess law says?
- that enthalpies of react are additive
- 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
- reverse reaction has the same __________ as that of the forward react, but its ________ is oppos
-
enthalpy,
but its sign is oppos - bond e or bond dissoc e is?
- averag of the energy req to break a part type of bond in one mole of gaseous molec
- bond ____________ is always endothermic
- breakage
- bond ______________ is always exothermic
- formation
-
H2 (g) ---> 2H (g)
ΔH= will be? - positive
- bond e can be used to estim the ?
- enthalpies of reactions
- ΔHreact can be estimated by?
- =(ΔH of bonds broken)- (ΔH of bonds formed)
- 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 - spectroscopy can be used to measure the bond dissoc e of?
- simple diatomic molecules
- what are the req for relatively easy measure of ΔH?
- that react be fast and spontan
- entropy is the meas of?
- disorder of a system
- what are units of entropy?
- j/K
- J/K are the units for ?
- entropy
- a solid has a lower entropy than a ?
- gas
-
t or f
entropy is a state function - T
- ΔS=Sfin- Sinit
- Sfin- Sinit
- qrev/T =
- ΔS
- ΔS= ?/T
- qrev/T
-
entropy
qrev is ? - the heat added to the syst undergoing a rever process.
- freezing has a ___________ in entropy
- decrease
- boiling has a ____________ in entropy
- increase
- second law of thermodyn says that?
- all spont proceed so that entropy of the systm plus its surr increases
- ΔSuniv >
- 0
- a sytm reaches its maxim entropy at?
- equilibrium
- for a revers procc ΔSuniv is?
- zero
- Gibbs free energy combines what 2 fact?
- ΔH and ΔS
- Goose hunters take shotguns reminds you of?
- ΔG=ΔH-TΔS
- ΔG=?
- ΔG=ΔH-TΔS
- in the equilbr state, free e is?
- at a minimum
- ΔG <0 means a proc can?
- occur spont
- for any given nonspont react or proc, the reverse react or proc will be?
- sponaneous
-
if ΔG is zero
the system is? - in a state of equil
-
thermody and kinetics
spontan does not necessaril mean? - instantaneous
-
ΔH ΔS Outcome ?
- + - spontaneous at all temperatures
-
ΔH ΔS
+ - - nonspontaneous at all temperatures
-
ΔH ΔS
+ + - spontaneous only at high temperatures
-
ΔH ΔS
- - - spontaneous only at low temperatures
- rate of a reac depends on?
- activat e
-
t or f
rate of a react dep on ΔG - f
- standard free energy ΔG is ?
- ΔG of a proc occur at 25 C and 1 atm . concentr of sol are 1 M
- standard free energy of format of a comp is?
- free energy ch that ocurs when 1 mol of a comp in its stand form
- standard free energy of format of any elem in its most stable form is?
- zero
- conversion of C (diamond) to C (graphite) is __________ but its rate is slow
- spont
- ΔG react=(sum of ΔGf of prod)- ??
- =(sum of ΔGf of prod)- (sum of =(sum of ΔGf of react)
- -RTlnKeq =
- ΔG
- what is the equat for ΔG from equil const?
- ΔG=-RTlnKeq
- once a react commences a standard state condit?
- no longer holds
- once a react commences Keq must be replac by?
- reaction quotient Q
- the react quotient Q is=
- Q=[C]^c[D]^d/[A]^a[B]^b
-
when a react commences
ΔG=? - ΔG= ΔG° + RTlnQ
- discuss when water boils in terms of ch in G
- TchS> chH only when T is above 373 K