Unit 7 - Chemical Equilibrium Flashcards

1
Q

What are example of reversible changes?

A

Phase changes
Dissolution/Precipitation
Gas absorption/Desorption

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2
Q

forward reaction

A

Going from left to the right

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3
Q

reverse reaction

A

going from right to left

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4
Q

What occurs at equilibrium?

A

Rate of forward reaction is equal to the rate of reverse reaction
no net observable changes
Constant concentrations

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5
Q

Does concentration have to be equal?

A

Does not have to be equal

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6
Q

What does Equilibrium is DYNAMIC mean?

A

Continues to occur at same rates

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7
Q

In order for a net conversion to reactants to happen,…

A

The rate of the forward reaction has to be smaller than the rate of the reverse reaction.
Reverse reaction is favored

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8
Q

In order for a net conversion to products to happen…

A

The rate of the forward reaction has to be bigger than the rate of the reverse reaction
forward reaction is favored

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9
Q

When neither direction is favored…

A

EQUILIBRIUM

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10
Q

What is the reaction quotient?

A

Represent the relative quantities of products to reactants at any given point in time

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11
Q

what is the reaction quotient for aA +bB cC dD

A

[C]^c [D]^d / [A]^a [B]^b

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12
Q

What happens to the reaction quotient expression when used in gas phase reactions?

A

Instead of concentration, written in pressures

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13
Q

What phases are included in a reaction quotient?

A

Only gases and aqueous solutions

Solids and liquids are not

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14
Q

Can Qp and Qc be interchangeable?

A

NO

Qp does not and can not equal Qc

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15
Q

What is the equilibrium constant?

A

Same properties as the rxn quotient

Used instead during equilibrium

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16
Q

What does the value of Q indicate?

A

Whether the rxn will need to proceed towards the left or right in order to achieve equilibrium

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17
Q

What does the value of K indicate?

A

Whether there are more products or reactants at equilibrium

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18
Q

In order to calculate K is temperature needed?

A

Temp is NOT needed to calculate K

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19
Q

The numerator of Keq represents what

A

Products

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20
Q

The denominator of Keq represents what

A

Reactants

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21
Q

In a rxn favoring products, the Keq is

A

Larger

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22
Q

In a rxn favoring reactants, the Keq is

A

smaller

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23
Q

What does the magnitude of K tell us?

A

How the concentrations of reactants and products compare at equilibrium

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24
Q

K > 1 implies

A

[products] > [reactants]

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25
Q

K approx 1 implies

A

[products] is about the same as [reactants]

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26
Q

K < 1 implies

A

[products] < [reactants]

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27
Q

Can K be less than zero

A

NOPE

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28
Q

A SUPER BIG K value indicates

A

100% in forward and near 0 in reverse

Equivalent to complete forward

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29
Q

A SUPER SMALL K value indicates

A

0% in forward and 100% in reverse

Equivalent to complete reverse

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30
Q

What K values does a rxn need to have at equilibrium to proceeds significantly in both directions?

A

B/t 0.1 and 10

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31
Q

What is the coefficient rule?

A

When coefficients are changed by a factor of n, Keq is raised to the power of n

32
Q

What is the reciprocal rule?

A

When a rxn is reversed the new Keq value is the inverse of the old Keq value

33
Q

What is the multiple equilibria rule?

A

When two or more rxns are combined the new Keq is the product of the Keq values from individual rxns

34
Q

If Q is larger than K

A

Numerator must decrease implies products must decrease

reverse rxn favored

35
Q

If Q is smaller than K

A

Numerator must increase implies products must increase

forward rxn favored

36
Q

What are the two sets of conditions as a rxn proceeds?

A

Initial conditions

Equilibrium conditions

37
Q

what are the two methods of determining eq conditions given initial conditions and k

A

Neglect X

Perfect squares

38
Q

What is the Neglect X method?

A

Only applicable when K is smaller than 0.0001
Remove x in the denominator
Negligible change and minimal effect

39
Q

Once x has been determined, how can you use x to find the eq concentration.

A

Substitute value back into ICE table

40
Q

ICE table

A

Initial
Change
Equilibrium

41
Q

What is the perfect squares method?

A

Only applicable when both num and den are perfect squares

Simply Sqrt both sides and simplify

42
Q

What does the LaChatelier principle state?

A

Changing rxn conditions of a system at eq can knock system out of eq causing stress
System will shift to reduce stress and achieve equilibrium again

43
Q

What can be changed to stress a system?

A

Molarity
Pressure
Volume
Temperature

44
Q

What happens with addition of reactants? decrease of products?

A

System will shift to consume reactants and produce products

45
Q

What happens with addition of products? decrease of reactants?

A

System will shift to consume products and produce reactants

46
Q

What happens when you dilute a solution?

A

Dilution causes all M to decrease/ rxn shift to side with greatest aq

47
Q

Concentration a solution?

A

Concentration causes all M to increase/rxn shift to side with least aq

48
Q

What happens in response to addition of a catalyst or solid?

A

No stress occur

49
Q

What happens in response to increased pressure or decreased volume?

A

Rxn shift to side with least moles of gas

50
Q

What happens in response to decreased pressure or increased volume?

A

Rxn shift to side with most moles of gas

51
Q

Higher temp favor what kind of rxn

A

Endothermic

52
Q

Lower temp favor what kind of rxn

A

Exothermic

53
Q

what happens to the K value in endo rxn

A

K new > K old

54
Q

What happens to K value in exo rxn

A

K old > K new

55
Q

If Q = to K then

A

equilibrium

56
Q

Keq only changes if

A

Temperature changes

57
Q

What is solutibility?

A

Denoted as S

Amount of a salt that will dissolve to form a saturated solution at a given temp

58
Q

Salts classified as insoluble are actually…

A

Slightly soluble

59
Q

Ksp

A

is the K for solutibility product

60
Q

Solubility constant in an 1:1 ion ratio is…

A

Ksp = S^2

61
Q

Solubility constant in an 1:2 ion ratio is…

A

Ksp =4S^3

62
Q

Solubility constant in an 1:3 ion ratio is…

A

Ksp =27S^4

63
Q

Solubility constant in an 2:3 ion ratio is…

A

Ksp =108S^5

64
Q

In order to calculate S

A

Set S equal to Ksp and simplify

65
Q

Presence of some solid in a rxn…

A

provides evidence that a solution is saturated

66
Q

Solubility is expressed in…

A

g/L or mol/L

67
Q

Soluble salts has a Ksp of….

A

> 1

68
Q

In order to compare the solubility of insoluble salts

A

Compare the S value

69
Q

Ksp can only be compared when…

A

Both salts have the same ion ratio

70
Q

The Qsp can be calculated with..

A

any or initial ion concentration

71
Q

The Ksp can be calculated with…

A

eq ion concentration

72
Q

If Ksp > Qsp, then a precipitate…

A

Will not form

Not enough ions and unsaturated solution

73
Q

If Ksp < Qsp, then a precipitate…

A

Will form

Saturated solution

74
Q

What is the common ion effect?

A

a common ion causes decreased solubility

75
Q

How to calculate S when a common ion is present

A

Use ICE Table
S is negligible in eq concentration + S
Set Ksp equivalent to S

76
Q

What is a neutralization rxn?

A

Acid +Base –> Water and Salt`

77
Q

Solubility of a class of slightly soluble compounds that contain hydroxide or conjugate base of a weak acid

A

Is highly sensitive to addition of acids or bases