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CHM 1120 > Equilibrium > Flashcards

Equilibrium Flashcards

1
Q

What is the half life 1st order equation?

A

t1/2 = .693/k

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2
Q

What is the half life second order equation?

A

t1/2 = 1/[A]0k

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3
Q

What is radioactive decay?

A

When some radioactive element gives off a particle that follows 1st order kinetics

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4
Q

What are the 3 forms of radioactive decay?

A

alpha, beta, gamma

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5
Q

What is alpha radioactive decay?

A

helium nuclei
Nucleus is too big
4/2 He, 4/2 𝛂
4 total mass, lost 2 protons

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6
Q

What is beta radioactive decay?

A

electron emitted from the nucleus
0/-1 𝝱

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7
Q

What is gamma radioactive decay?

A

electromagnetic radiation
Promote electrons in energy levels
238/92 U β†’ 4/2 He + 234/90 Th
238/92 U β†’ 0/-1 𝝱 + 239/92 Np

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8
Q

What is carbon dating?

A

14C is a naturally occurring radioactive isotope. It’s present at a constant level in the atmosphere because it is constantly replenished by solar radiation in the upper atmosphere

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9
Q

What is the constant level of carbon?

A

1 14C / 1x10to the12 12C
everything that breathes has this ration

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10
Q

How can the age of formerly living objects be determined by?

A

by how much 14C has decayed because the decay follows 1st order kinetics

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11
Q

What is the Arrhenius equation?

A

K = Ae to the (-Ea/RT)

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12
Q

What is k in the arrhenius equation?

A

rate constant

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13
Q

What is A in the arrhenius equation?

A

frequency factor (takes into account the orientation and the likelihood of a collision to result in reaction)
Arrhenius constant
Statistical
Units are the same as the rate constant

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14
Q

What is R in the arrhenius equation?

A

gas constant (8.314 J/molK = .008314 kJ/molK)

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15
Q

What is E sub a in the arrhenius equation?

A

activation energy (kJ or J)
The higher the activation energy, the slower the reaction
proportional to 1/k

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16
Q

What is the relationship in between activation energy and rate constant?

A

inverse
As activation energy increases, k decreases

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17
Q

What is T in the arrhenius equation?

A

temperature (Kelvin)
As temperature increases, k increases
Proportional to each other
Makes rate go up

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18
Q

What is the linear Arrhenius equation?

A

lnk = -Ea/R (1/T) + lnA
y = mx + b

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19
Q

Does the value of k change when temperature changes?

A

yes

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20
Q

Can the activation energy be negative?

A

no

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21
Q

What is the Arrhenius equation with 2 temperatures?

A

ln(k1/k2) = Ea/R (1/T2 - 1/T1)
No frequency factor (A)

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22
Q

What happens to k as temperature increases? Decreases?

A

increases, decreases

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23
Q

What are catalysts?

A

molecule added to a reaction that increases the reaction rate

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24
Q

What happens to true catalysts?

A

True catalysts are regenerated at the end of the reaction

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25
Q

What do catalysts provide?

A

a new pathway for the same reaction, but with a lower activation energy
A pathway with a lower activation energy has a faster rate
The activation energy is fixed and does not change, so new pathways are created for the reaction, so it is a different reaction but with the same result
Avoids the reaction barrier

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26
Q

What are irreversible reactions?

A

All reactants are used up
All products formed
Very few irreversible reactions

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27
Q

What are reversible reactions?

A

Reaction can occur in both directions
Both reactants and products are present at the same time, even at the β€œend” of the reaction
Each direction has its own rate and rate law

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28
Q

Do reactants become products and products become reactants in reversible reactions?

A

yes

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29
Q

Does the forward rate of reaction decrease or increase over time?

A

decrease

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30
Q

Does the reverse rate of reaction decrease or increase over time?

A

increase

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31
Q

Do the forward and reverse reaction turn into each other at the same rate?

A

yes

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32
Q

Do reactants decrease or increase in concentration over time?

33
Q

Do products decrease or increase in concentration over time?

34
Q

What happens to concentration when equilibrium is established?

A

concentration remains constant

35
Q

Do concentrations change in equilibrium?

36
Q

What is it called when concentrations do not change anymore?

A

dynamic equilibrium

37
Q

Do forward and reverse reactions take place at the same time?

38
Q

Are the ratio of products to reactants, (products/reactants), fixed and always the same?

39
Q

What is the reaction quotient, Q?

A

1) Ratio of (products/reactants) at any time during the reaction when it is not at equilibrium
2) Can approach equilibrium from either reaction direction
3) Q is represented as the ratio of concentrations raised to the power of their coefficients
4) aA+bB ←→ cC+dD
5) Q= [C]c[D]d / [A]a[B]b
6) Constantly changes as the reaction proceeds towards equilibrium

40
Q

What does Q equal when equilibrium is reached?

41
Q

When is Q less than K?

A

Reactants β†’ products

42
Q

When is Q larger than K?

A

Reactants ← products

43
Q

What is the equilibrium constant, K?

A

1) Ratio of (products/reactants) at equilibrium. Like Q, it is a ratio of concentrations raised to the power of their coefficients
2) K= [C]c[D]d / [A]a[B]b
3) Can be represented as either a ratio of product to reactant concentrations or a ratio of rate constants
4) N2O4 ←→ 2NO2
5) 2 different reactions, forward and reverse
6) Rateforward = kf[N2O4]1
7) Ratereverse = kr[NO2]2

44
Q

Is the equilibrium rate of the forward reaction equal to the rate for the reverse reaction?

A

1) yes
2) rate laws are equal to each other
3) kf[N2O4]1 = kr[NO2]2
4) Can group all concentrations on one side and all rate constants on the other side
5) kf/kr = [NO2]2 / [N2O4]1 = K (equilibrium constant)

45
Q

What are the characteristics of K?

A

1) K is constant at constant temperature
2) Changes with changing temperature
3) Multiple values for concentrations can have the same value of K
4) NO units
5) K is always positive, never negative or 0
6) aA+bB←→cC+dD
7) K= [C]c[D]d / [A]a[B]b
8) Kc (c stands for concentration) = Keq (eq stands for equilibrium)

46
Q

What are the characteristics of Q>K and what way is the reaction proceeding?

A

Numerator is too large and denominator is too small compared to values at equilibrium
Reaction proceeds in the direction that will lower the numerator and increase the denominator
Backwards

47
Q

What are the characteristics of Q<K and where is the reaction proceeding?

A

Numerator is too small and denominator is too big compared to values at equilibrium
Reaction proceeds in the direction that increases the numerator and decreases the denominator
forwards

48
Q

What is Le Chatelier’s Principle?

A

When a chemical system at equilibrium is disturbed, it reattains equilibrium by undergoing a net reaction that reduces the effect of the disturbance

49
Q

What are the 2 major paths to perturbing equilibrium states?

A

1) Change concentrations of reactants or products
- add or remove reactants
-add or remove products
2) Change reaction temperature
-adding or removing heat
-change depends on whether reaction is exothermic or endothermic

50
Q

Is heat a product or a reactant in exothermic reactions?

51
Q

Is heat a product or a reactant in endothermic reactions?

52
Q

What does it mean if K is smaller than 1?

A

more reactant

53
Q

What does it mean when K is larger than 1?

A

more product

54
Q

Are K and X directly or inversely proportional?

A

directly
Larger K = bigger X
Smaller K = smaller X

55
Q

What does it mean for X if the value of K is 100x or more smaller than the smallest initial concentration?

A

X is negligible

56
Q

What does increasing the temperature of an exothermic reaction do?

A

shifts reaction to the left

57
Q

What does decreasing the temperature in an exothermic reaction do?

A

shifts the reaction to the right

58
Q

What does increasing the temperature of an endothermic reaction do?

A

shifts reaction to the right

59
Q

What does decreasing the temperature of an endothermic reaction do?

A

shifts reaction to the left

60
Q

Does solubility increase when temperature is increased in endothermic reactions?

61
Q

Are products or reactants favoured when K is smaller than 1?

62
Q

Are products or reactants favoured when K is larger than 1?

63
Q

What predicts reaction direction?

A

𝚫G and Q vs K

64
Q

Which way does the reaction proceed if 𝚫G is negative?

65
Q

Which way does the reaction proceed if 𝚫G is positive?

66
Q

What way does the reaction proceed when Q<K?

67
Q

What way does the reaction proceed when Q>K?

68
Q

What is the equation between 𝚫G and equilibrium?

A

𝚫G = RT lnQ - RT lnK

69
Q

What does 𝚫G measure?

A

how different the concentrations at Q are from K (equilibrium)

70
Q

What does it mean when Q and K are very different?

A

the reaction releases/absorbs a large amount of free energy

71
Q

What does it mean when Q and K are not very different?

A

the reaction releases/absorbs a small amount of free energy

72
Q

What value does Q become at standard state?

A

1 because all concentrations are 1.00M and ln1=0

73
Q

1) What is the alternate equation when reactions don’t start at 1.00M?
2) What does this allow us to determine?

A

1) 𝚫Grxn =𝚫G0 rxn + RT ln Q
2) relationship between 𝚫G0 and 𝚫G at any starting position and allows us to calculate K from 𝚫G0 and vice versa

74
Q

Are weak acids and bases reversible?

75
Q

What do we define reactions that do not react completely?

A

ionization or % ionization
- they form ions

76
Q

What is the Brontsted-Lowry definition of an acid?

A

proton donor
Must have a donatable H+
Increase the concentration of [H3O+] (hydronium) in water
HCl + H2O β†’ Cl- + H3O+
Positive and negative ions

77
Q

What is the Bronsted-Lowry definition of a base?

A

proton acceptor
Must ave a lone pair of electrons to accept the H+
Increase the concentration of [OH-] (hydroxide) in water
OH- + H2O β†’ H2O +OH-
Oxygen has 3 lone pairs, steals electrons from Hydrogen

78
Q

Is there equilibrium involved with weak acids?

CHM 1120 (4 decks)

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