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Chem1120 > unit 4 > Flashcards

unit 4 Flashcards

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1
Q

define ENTHALPY

A

heat transferred in rxn @ constant P

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2
Q

__ is produced when reactants turn into products completely

A

enthalpy

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3
Q

define EQUILIBRIUM

A

when the forward and reverse reactions happen at equal rates

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4
Q

what letter represents equilibrium

A

K

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5
Q

define SPONTANEOUS CHANGE

A

change that happens w/o continuous input of energy

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6
Q

spontaneous change only needs

A

the initial activation energy

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7
Q

define NONSPONATNEOUS CHANGE

A

change that only happens if continous energy is supplied

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8
Q

t/f: if a rxn is spontaneous in 1 direction it is nonspontaneous in the rev direction

A

true

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9
Q

t/f: the direction of spontaneous change can be predicted using energy or the sign of delta H

A

false, the direction of spontaneous change CANNOT be solely predicted by energy or sign of delta H

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10
Q

give examples of exothermic spontaneous changes

A
  • freezing & condensation at low temp
  • combustion rxns
  • oxidation of metals
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11
Q

give examples of endothermic spontaneous changes

A
  • melting & vaporization at increased temperature
  • dissolving of soluble salts
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12
Q

t/f: systems at equilibrium are reversible

A

true

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13
Q

t/f: spontaneous rxns that are not in equilibrium are reversible

A

false, they are not reversible if not at equilibrium

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14
Q

__ tells the direction of a rxn

A

thermodynamics

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15
Q

__ tells the speed of a rxn

A

kinetics

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16
Q

all spontaneous endothermic rxns leads to an ___ in freedom of particle motion

A

increase

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17
Q

what is a key factor that affects direction of spontaneous processes

A

changes in freedom of particle motion

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18
Q

define MICROSTATE

A

quantized energy state for system of particles

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19
Q

the total energy of a system is dispered through out ___ microstate

A

one

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20
Q

t/f: each microstate differs in total energy

A

false, each microstate has the same total energy as any other

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21
Q

an increase in number of possible microstates leads to an __ in number of ways a system can disperse its energy

A

increase

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22
Q

define ENTROPY

A

state function of disorder

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23
Q

t/f: entropy is dependent on the path between final and initial states

A

false, it is independent of the path between final and initial states

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24
Q

all spontaneous ___ processes show an increase in entropy

A

endothermic

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25
a decrease in microstates leads to a __ in entropy
decrease
26
a __ in microstates leads to an increase in entropy
increase
27
an increase in volume leads to an __ in energy levels which leads to an increase in ___ which causes an increase in ___
increase; number of microstates; entropy
28
define REVERSIBLE PROCESS
process that happens in tin increments so the rxn is at equilibrium
29
in a reversible process, the direction of change can be reversed by ___ changes
very small
30
t/f: all real processes happen spontaneously in the direction that increases entropy of universe
true
31
a decrease in entropy offset by a larger __ in entropy of surroundings produces a spontaneous process
increase
32
t/f: the total energy of the universe varies
false, it remains constant
33
what is can generally be used to approximate delta E
delta H
34
is there a zero point for enthalpy?
no
35
is there a zero point for entropy?
yes
36
a perfect crystal has __ entropy and absolute zero
zero
37
why does a perfect crystal have zero entropy at absolute zero
flawless alignment of particles and minimum energy
38
define STANDARD MOLAR ENTROPY
entropy for substance in its standard state
39
list conditions that cause standard molar entropy to increase
- temp increase - when gases become solids/liquids - when moles of gases increase - with chemical complexity - most freedom of motion - molecules of same type
40
t/f: the standard molar entropy of substances can be compared if they are in the same physical state
false
41
an increase in heat causes an increase in ___ which leads to an __ in entropy
total energy dispersion; increase
42
entropy of fusion and vaporization can be seen on which part of a phase diagram
during phase change
43
t/f: entropy of a salt solution is more than the solid and water
true
44
t/f: entropy decreases when gas is dissolved in a liquid
true
45
entropy decreases for larger atoms
false, it increases
46
define STANDARD ENTROPY OF RXN
entropy changes when all reactants and products are in standard states
47
the sign of standard entropy of rxn (delta Srxn) changes with
the number of moles of gas
48
delta Suniv is __ when at equilibrium
zero
49
t/f: Suniv must be negative for spontaneous rxns
false, it must be positive
50
define FREE ENERGY CHANGE
spontaneity of process and useful energy available from it
51
if delta G is less than zero (negative) it is
spontaneous
52
if delta G is more than zero (positive) it is
not spontaneous
53
if delta G is equal to 0 it is
at equilibrium
54
what is delta Gf
free energy change when 1 mol of compound is formed from its constitutent elements w/all components in standard states
55
what is deltaGf of an element
0 kj/mol
56
what is delta G in a spontaneous rxn
maximum useful work done BY system in spontaneous rxn
57
what is delta G in a nonspontaneous rxn
minimum work done TO system to make nonspontaneous rxn happen
58
t/f: delta Hsys is independent of T
true
59
t/f: coupled rxns do not have to physically connected
false, they must be in physical contact
60
if delta H is neg, delta S is pos, -TdeltaS is neg, and delta G is neg, describe the reaction's relationship with spontaneity and temp
spontaneous at all temp
61
if delta H is pos, delta S is neg, -TdeltaS is pos, and delta G is pos; describe the rxn's relationship with spontaneity and temp
nonspontaneous at all temp
62
if delta H is pos, delta S is pos, -TdeltaS is eng, and delta G is either pos or neg; describe the rxn's relationship with spontaneity and temp
- spontaneous at higher temps - nonspontaneous at lwoer temps
63
if delta H is neg, delta S is neg, -TdeltaS is pos, and delta G is either neg or pos; describe the rxn's relationship with spontaneity and temp
- spontaneous at lower temp - nonspontaneous at higher temp
64
if delta G is more positive what happens to K
K gets smaller
65
if delta G is more negative, what happens to K
K gets bigger
66
define REDOX RXN
rxn that involves transfer of electrons
67
define OXIDATION
loss of electrons
68
define REDUCTION
gain of electrons
69
define OXIDIZING AGENT
reactant that gets reduced
70
define REDUCING AGENT
reactant that gets oxidized
71
define HALF RXN METHOD
divide redox rxns into oxidation & reduction half rexns
72
define ELECTROCHEMICAL CELL
system incorporating redox rxn to produce/use electrical energy
73
define VOLTAIC/GALVANIC CELL
electrochemical cell using spontaneous redox rxns to generate electrical energy
74
t/f: voltaic cells do work on the system rather than the surroundings
false, voltaic cells do work on the surroundings
75
define ANODE
electrode where oxidation happens
76
define CATHODE
electrode where reduction happens
77
define LOAD
external circuit connecting half cells where chemical energy is converted into electrical energy
78
define SALT BRIDGE
maintains electroneutrality of half-cell solutions
79
why do spontaneous rxns happen (in voltaic cells)
bc of differences in abilities of metals to give up electrons
80
define VOLTAGE/ELECTROMOTIVE FORCES
differences in electrical potential between 2 electrodes
81
the more psoitive Ecell is the __ work the cell can do which furthers the rxn to the ___
more; right
82
define STANDRD CELL POTENTIAL
cell potential at specific temp with no flowing current and all components in standard states
83
define STANDARD ELECTRODE POTENTIAL
potential of given half reaction when all components in standard states
84
define STANDARD HYDROGEN ELECTRODE
standard electrode potential = 0
85
why do Ehalf cell values reflect the reactant's ability as an oxidizing agent
bc all reactions are referred to as reductions
86
a more positive E half cell value means it is more likely to ___
reduce
87
a more negative E half cell value means it is more likely to __
oxidize
88
stronger oxidizing & reducing agents react spontaneously to form
weaker ones
89
a spontaneous redox rxn will happen between an oxidizing agent and any reducing agent that lies __ it in the EMF series
below
90
a half rxn higher in the emf list is written as a
cathode
91
a half rxn lower in the emf list is written as
anode in reverse

Chem1120 (4 decks)

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