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CHM 129 > Exam 3 > Flashcards

Exam 3 Flashcards

Lectures 27-35

1
Q

equilbirum

A

rate fwd = rate rev
* appears to be no change occuring
* collisions still occuring

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2
Q

dynamic equilbirum

A

rate fwd = rate rev
chemicals are consumed and made at the same rate, not necessarily the same concentration

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3
Q

equilbrium favors products

A

rxns that reach equilbirum after almost all reactant molecules are consumed

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4
Q

equilibrium favors reactants

A

rxns that reach equilbirum after a small percentage of reactant molecules are consumed

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5
Q

equilibrium systems are ___ and ___

A

dynamic
reversible

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6
Q

what 2 factors do not change at equilbrium in a closed system

A

concentration and pressure

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7
Q

law of mass action

A

if the system is at eq. at a given temp, then the ratio of product concentration and reactant concentration is constant
* k or kc

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8
Q

eq constant for rxns with gases

A

can be expressed as the ratio of the partial pressures of the gasses

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9
Q

which states of matter are not included in the expression of the eq constant

A

solids and liquids

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10
Q

why are solids and liquids not included in Q and k equations

A

their [ ] are constant

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11
Q

if keq = a very large number…

A

there is way more product than reactant

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12
Q

if keq = a very small number…

A

way more reactant than product

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13
Q

reaction quotient

A

ratio of [ ]s and/or pressures of the products and reactants in a mixture that may or may not be at equilbirum

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14
Q

which way does the system need to shift when Qc<Kc

A

right

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15
Q

which way does the system need to shift when Qc>Kc

A

left

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16
Q

difference between Qc and Kc

A

Qc is at any time during the reaction
Kc is at eq

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17
Q

for endothermic rxns, is heat a product or reactant

A

reactant

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18
Q

for exothermic rxns, is heat a reactant or product

A

product

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19
Q

relationship between pressure and volume

A

inverse

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20
Q

what 2 conditions regarding gases have no effect on eq

A
  1. inert gases
  2. moles of gas particles are equal on both sides
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21
Q

how does adding a catalyst effect eq and k

A

it does not, just makes system reach eq faster

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22
Q

La Chatelier’s Principle

A

whenever you force a change on a system at eq, the system will move ina way to undo that change

23
Q

intert gas

A

noble gas

24
Q

partial pressure

A

pressure exerterted by an individual gas in a mixture

25
Q

relationship between partial pressure and concentration

A

direct

26
Q

given k, what is k’ if the second equation is
1. doubled
2. halved
3. flipped

A
  1. k^2=k’
  2. k^1/2=k’
  3. 1/k=k’
27
Q

when do you make an ICE table

A

when the Molarity is not at eq

28
Q

remember

A
  • for kc, if both the numerator and denominator are squared, square root both sides of equation rather than expanding it
29
Q

when can you use the 5% or 400 rule

A

when kc<=a numberx10^-4

30
Q

5% rule

A

if (x/number before the -x)*100<=5

31
Q

what do you do if kc is not a very small number

A

quadratic formula

32
Q

after the quadratic formula, how do you know which x is correct

A

the x that’s not negative
* if both are positive, it’s the x that’s less than the starting amount of molarity

33
Q

Arrhenius Theory (must be in water)

A
  • acid: has H+, dissociates in H2O to form H3O+ and negative ions
  • base: has OH group, dissociates in H2O to form OH- and positive ions
34
Q

Bronsted-Lowry Theory

A
  • acid: proton donor
  • base: proton acceptor (doesn’t need OH, has lone pair to accept H+)
35
Q

Lewis Theory

A
  • acid: accepts an electron pair (doesn’t need to have hydrogen)
  • base: donates an electron pair (doesn’t need to have an OH)
36
Q

base

A

nucleophile: electron-rich

37
Q

acid

A

electrophile: electron-poor

38
Q

___ dissolve fully in water

A

salts

39
Q

monoprotic acid

A

can donate 1 H+

40
Q

diprotic acid

A

cane donate 2 H+

41
Q

polyprotic acid

A

can donate >1 H+

42
Q

Steps for ICE table

A
  1. write balanced eq
  2. ICE table
  3. write ka equation and plug in values from E of ICE
  4. set equal to ka value given
  5. use 5% or 400 rule
  6. solve for x
  7. use x to find whatever the question asks for (pH or eq [ ])
43
Q

buffer

A

when present in solutions, they prevent dramatic changes in pH when an acid or base is added

44
Q

what is a buffer made out of

A
  • weak acid and its conjugate base with a salt
  • weak base and its conjugate acid with a salt
45
Q

log sig fig rules

A

sig figs in answer after decimal point is the same number of sig figs in log
* in other words, sigs figs of number inside log() is the number of sig figs after the decimal point in the answer

ex. log 4.000 (4 s.f.) = 0.6021(4 s.f. to right of the decimal point)

46
Q

buffering capacity

A

amount of acid or base a buffer can neutralize

47
Q

when is the higher buffering capacity

A

[A-]=[HA] b/c pH=pka+log([A-]/[HA])

48
Q

buffering range

A

pH range the bugger can be effective

49
Q

when choosing an acid to make a buffer, which one do you pick

A

acid whose pka is closest to the pH of the bugger

50
Q

what equation do you use to calculate the pH of a buffer

A

henderson-hasselbalch

51
Q

inert gas

A

noble gas

52
Q

when does kp=kc

A

when the number of moles of products and reactants are equal
b/c kp=kc(RT)^n

53
Q

order of proton removal in amino acids

A

acidic - COOH, R-group, amino group
basic - COOH, amino group, R-group
neutral - COOH, amino

CHM 129 (4 decks)

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