45 Cards in this Set
| Front | Back |
|---|---|
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ΔS is __ for every spontaneous process
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positive
|
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if ΔSuniv is positive, the reaction is
|
spontaneous
|
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if ΔSuniv is negative the reaction is
|
not spontaneous
|
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heat flows from system to surroundings = ?
ΔHsys = ?
ΔHsurr = ?
ΔSsurr = ?
|
exothermic
-
+
+
|
|
heat flows from surroundings to system = ?
ΔHsys = ?
ΔHsurr = ?
ΔSsurr = ?
|
endothermic
+
-
-
|
|
for spontaneity:
TΔSuniv = -ΔHsys + TΔSsys is greater than or less than zero?
|
greater than
|
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for spontaneity:
-TΔSuniv = ΔHsys - TΔSsys is greater than or less than zero?
|
less than
|
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equation for Gibb's free energy
|
ΔG = ΔH - TΔS
|
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if ΔG is negative:
|
reaction is spontaneous
increase in Suniv
|
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if ΔG is positive:
|
reaction is not spontaneous
decrease in Suniv
reverse reaction is spontaneous
|
|
when ΔG = 0 the system is at
|
equilibrium
|
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best ΔGrxn
|
exothermic and positive ΔS
ΔH = - (good)
ΔS = + (good)
ΔG is always negative so the reaction is always spontaneous
|
|
what ΔGrxn will never happen?
|
endothermic and negative ΔS
ΔH = + (bad)
ΔS = - (bad)
|
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what ΔGrxn is better at low temperatures?
|
exothermic and negative ΔS
ΔH = - (good)
ΔS = - (bad)
|
|
what ΔGrxn is better at higher temperatures?
|
endothermic and positive ΔS
ΔH = + (bad)
ΔS = + (good)
|
|
if K is large and ΔGrxn° is negative; which direction is favorable?
|
forward
|
|
oxidation is always accompanied by a
|
reduction
|
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do oxidation numbers change?
|
yes
|
|
oxidizing agent
|
gets reduced
gains electrons
becomes more negative
(causes oxidation of something by taking e-)
|
|
reducing agent
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gets oxidized
loses electrons
becomes more positive
(causes reduction of something by giving e-)
|
|
assigning oxidation #s:
free elements
|
0
|
|
assigning oxidation #s:
monoatomic ion
|
charge
|
|
assigning oxidation #s:
in compounds, ox # of O = __ except with __ then it equals __
|
-2
peroxides (H2O2)
-1
|
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assigning oxidation #s:
in compounds, ox # of H = __ except in __ ___ then ox # =
|
1
metal hydrides
-1
|
|
assigning oxidation #s:
halogens
F is always __
Cl, Br, I also __, unless with __ or __, then the other rules apply __
|
-1
-1
F, O
first
|
|
assigning oxidation #s:
molecules
|
sum of ox #s = 0
|
|
Anode is oxidation or reduction?
|
Oxidation
|
|
Cathode is oxidation or reduction?
|
Reduction
|
|
Cell diagram:
One line (l)
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Phase boundary
|
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Cell diagram:
Two lines (ll)
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Salt bridge
|
|
Where would you clip the wire to on cell diagrams
|
The ends
The solids
|
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Standard conditions for solutes and gases
|
1.00 M and 1.00 atm
|
|
sign of a spontaneous Eºcell
|
positive (+)
|
|
table:
top to bottom
|
more likely to run as written
|
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table:
bottom to top
|
more likely to run the reverse
|
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total charge
|
nF
|
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when the oxidation v is positive what does that say?
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very favorable oxidation, but not a favorable reduction
|
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chemical energy to electrical energy is
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spontaneous
|
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electrical energy to chemical energy is
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not spontaneous
|
|
another term for not spontaneous
|
electrolysis
|
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for electrolysis, how much voltage has to be applied?
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whatever Eºcell is plus a little
|
|
can you do electrolysis in water?
|
no
|
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with electrochemistry you always get the reaction that's the (most or least) unfavorable
|
least (easiest)
|
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can't do electrolysis if more negative than what number?
|
-1.23 v
|
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what would happen if you did electrolysis and number was less than -1.23
|
you'd make water
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CHM 104: EXAM 4