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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
What do catalysts provide?
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
26
What are irreversible reactions?
All reactants are used up All products formed Very few irreversible reactions
27
What are reversible reactions?
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
28
Do reactants become products and products become reactants in reversible reactions?
yes
29
Does the forward rate of reaction decrease or increase over time?
decrease
30
Does the reverse rate of reaction decrease or increase over time?
increase
31
Do the forward and reverse reaction turn into each other at the same rate?
yes
32
Do reactants decrease or increase in concentration over time?
decrease
33
Do products decrease or increase in concentration over time?
increase
34
What happens to concentration when equilibrium is established?
concentration remains constant
35
Do concentrations change in equilibrium?
no
36
What is it called when concentrations do not change anymore?
dynamic equilibrium
37
Do forward and reverse reactions take place at the same time?
yes
38
Are the ratio of products to reactants, (products/reactants), fixed and always the same?
yes
39
What is the reaction quotient, Q?
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
What does Q equal when equilibrium is reached?
K
41
When is Q less than K?
Reactants β†’ products
42
When is Q larger than K?
Reactants ← products
43
What is the equilibrium constant, K?
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
Is the equilibrium rate of the forward reaction equal to the rate for the reverse reaction?
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
What are the characteristics of K?
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
What are the characteristics of Q>K and what way is the reaction proceeding?
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
What are the characteristics of Q
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
What is Le Chatelier's Principle?
When a chemical system at equilibrium is disturbed, it reattains equilibrium by undergoing a net reaction that reduces the effect of the disturbance
49
What are the 2 major paths to perturbing equilibrium states?
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
Is heat a product or a reactant in exothermic reactions?
product
51
Is heat a product or a reactant in endothermic reactions?
reactant
52
What does it mean if K is smaller than 1?
more reactant
53
What does it mean when K is larger than 1?
more product
54
Are K and X directly or inversely proportional?
directly Larger K = bigger X Smaller K = smaller X
55
What does it mean for X if the value of K is 100x or more smaller than the smallest initial concentration?
X is negligible
56
What does increasing the temperature of an exothermic reaction do?
shifts reaction to the left
57
What does decreasing the temperature in an exothermic reaction do?
shifts the reaction to the right
58
What does increasing the temperature of an endothermic reaction do?
shifts reaction to the right
59
What does decreasing the temperature of an endothermic reaction do?
shifts reaction to the left
60
Does solubility increase when temperature is increased in endothermic reactions?
yes
61
Are products or reactants favoured when K is smaller than 1?
reactants
62
Are products or reactants favoured when K is larger than 1?
products
63
What predicts reaction direction?
𝚫G and Q vs K
64
Which way does the reaction proceed if 𝚫G is negative?
forward
65
Which way does the reaction proceed if 𝚫G is positive?
reverse
66
What way does the reaction proceed when Q
forward
67
What way does the reaction proceed when Q>K?
backward
68
What is the equation between 𝚫G and equilibrium?
𝚫G = RT lnQ - RT lnK
69
What does 𝚫G measure?
how different the concentrations at Q are from K (equilibrium)
70
What does it mean when Q and K are very different?
the reaction releases/absorbs a large amount of free energy
71
What does it mean when Q and K are not very different?
the reaction releases/absorbs a small amount of free energy
72
What value does Q become at standard state?
1 because all concentrations are 1.00M and ln1=0
73
1) What is the alternate equation when reactions don't start at 1.00M? 2) What does this allow us to determine?
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
Are weak acids and bases reversible?
yes
75
What do we define reactions that do not react completely?
ionization or % ionization - they form ions
76
What is the Brontsted-Lowry definition of an acid?
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
What is the Bronsted-Lowry definition of a base?
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
Is there equilibrium involved with weak acids?
yes

CHM 1120 (5 decks)

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