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Chem - Gr11 > Equilibrium > Flashcards

Equilibrium Flashcards

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1
Q

Equilibrium state

A

An equilibrium state is a system condition where there is no change over time, and any change in one direction is balanced by a change in the opposite direction

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2
Q

Dynamic Equilibrium

A

Dynamic equilibrium is a state where opposing forces or reactions reach a balance, resulting in stability over time.

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3
Q

Equilibrium Mixture

A

Mixture of reactants and products in the equilibrium state

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4
Q

Ionic Equilibrium

A

Ionic equilibrium is the state of balance between ions and unionized molecules in a solution of weak electrolytes

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5
Q

Equilibrium for solid-liquid

A
  • Rate of melting = Rate of freezing
  • Both processes occur simultaneously
  • Both processes occur at the same rate
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6
Q

Normal Freezing Point / Normal Melting Point

A

Temperature at which the solid and liquid phases are at equilibrium at atmospheric pressure

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7
Q

Liquid Vapour Equilibrium

A

Rate of evaporation = Rate of condensation
* IMPORTANT: NEEDS TO HAPPEN IN A CLOSED VESSEL OTHERWISE REVERSE PROCESS WILL NOT HAPPEN

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8
Q

Equilibrium vapour pressure / Vapour pressure of liquid

A

Pressure exerted by vapours in equilibrium with the liquid at a particular temperature

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9
Q

Normal Boiling Point

A

Temperature at which the liquid and vapours are at equilibrium

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10
Q

Relation between boiling point and atmospheric pressure

A

Inversely proportional
At high altitude = BP decreases

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11
Q

Solid Vapour equilibrium

A

Can be explained by iodine
After sometime vessel gets filled up with violet vapour and intensity of colour increases with time

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12
Q

Solids in Liquids

A

Sugar solution

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13
Q

Saturated Solution

A

When no more of a solute can be dissolved in it at a given temperature

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14
Q

Gases in liquids

A

A soda water bottle opened (giving CO2)

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15
Q

State Henry’s Law

A

Mass of a gas dissolved in a given mass of a solvent at any temperature is proportional to the pressure of the gas above the solvent

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16
Q

Tell the processes and conclusions attained:
1. Liquid to vapour (H2O liq. to H2O gas)
2. Solid to liquid (H2O solid to H2O liq)
3. Solute (s) to Solute (solution)
4. Gas (g) to Gas (aq)

A
  1. pH2O constant at given temperature
  2. Melting point is fixed at constant pressure
  3. Concentration of solute in a solution is constant at a given temperature
  4. Gas (aq) / Gas (g) is constant at a given temp
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17
Q

Equilibrium equation

A

kc (equilibrium constant) = [C][D] / [A][B]

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18
Q

Equilibrium equation for general equation

A

aA + bB –><– cC + dD
Kc = [C]^c [D]^d / [A]^a [B]^b

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19
Q

Equilibrium constant unit

A

mol L^-1

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20
Q

Equilibrium Law / Law of Chemical Equilibrium

A

Products of concentrations of reaction products raised to the respective stoichiometric coefficient in the balanced chemical equation divided by the product of concentrations of the reactants raised to their individual stoichiometric coefficients has a constant value

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21
Q

Homogenous Equilibrium

A

All reactants and products are in the same phase

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22
Q

Relation betwen pressure and conc. at constant temperature

A

Proportional
p = [gas]RT

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23
Q

Difference between Kc and Kp

A

The main difference between Kc and Kp is that Kc is the equilibrium constant expressed in terms of concentration, while Kp is expressed in terms of pressure

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24
Q

General equation with Kp

A

For aA + bB -><- cC + dD
Kp = Kc (RT)^delta n
Where delta n = no. of moles of gaseous products - no. of moles of gaseous reactants

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25
Q

Bar into Pa

A

1 bar = 10^5 Pa

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26
Q

Heterogeneous Equilibrium

A

System having more than one phase

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27
Q

Concentration of pure liquid or solid

A

Taken as constant (independent of amount present)
Gaseous and aq. will vary

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28
Q

Important features of eq. constant

A
  1. Expression for eq. const. applicable only when conc. of react. and prod. attained constant value
  2. Independent of initial concentrations of react and prod
  3. Temperature dependent
  4. K of forward = 1 / K of backward
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29
Q

What happens when Kc > 10^3

A
  • Products predominate
  • Reaction proceeds nearly to completion
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30
Q

If Kc < 10^-3

A
  • Reactants predominate over products
  • Reaction rarely proceeds
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31
Q

Kc between 10^-3 and 10^3

A

Appreciable concentrations of both reactants and products present

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32
Q

Reaction quotient (Q)

A

The reaction quotient, or Q, is a measurement of the relative amounts of products and reactants in a chemical reaction at a specific time

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33
Q

What happens when:
1) Qc > Kc
2) Qc < Kc
3) Qc = Kc

A
  1. Reaction will proceed in direction of reactants (reverse reaction)
  2. Will proceed in direction of products (forward reaction)
  3. At equilibrium
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34
Q

k value in terms of g

A

k = e ^ (-G eq / RT)

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35
Q

What happens when G < 0

A

-G/RT > 0;
K > 1;
spontaneous reaction;
proceeds in a forward direction

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36
Q

What happens when G > 0

A

-G/RT < 0;
K < 1;
non - spontaneous reaction;
proceeds in a backward direction

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37
Q

Le Chatelier’s Principle

A

Change in any of the factors that determine the equilibrium conditions of a system will cause the system to change in such a manner so as to reduce or to counteract the effect of the change

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38
Q

G value in terms of k

A

G = -RT ln Kc

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39
Q

Concentration change (Le Chaterlier’s Principle)

A

When concentration of any of the reactants or products in a reaction at equilibrium is changed, the composition of the equilibrium mixture changes so as to minimize the effect of concentration changes

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40
Q

Increase in concentration of reactant

A
  • According to Le Chatelier’s principle, such a change in the sytem will have to counteract the change
  • As concentration of reactants is higher, Qc is now much lower
  • Qc < Kc means the reaction will move in the forward direction
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41
Q

Increase in concentration of product

A
  • According to Le Chatelier’s principle, such a change in the sytem will have to counteract the change
  • As concentration of products is higher, Qc is now much higher
  • Qc > Kc means the reaction will move in the backward direction
42
Q

Decrease in concentration of product (Removal)

A
  • According to Le Chatelier’s principle, such a change in the sytem will have to counteract the change
  • As concentration of reactants is higher, Qc is now much lower
  • Qc < Kc means the reaction will move in the forward direction
43
Q

Decrease in concentration of reactant (Removal)

A
  • According to Le Chatelier’s principle, such a change in the sytem will have to counteract the change
  • As concentration of products is higher, Qc is now much higher
  • Qc > Kc means the reaction will move in the backward direction
44
Q

Effect of pressure change:
N2(g) + 3H2(g) –><– 2NH3(g)

A
  • An increase in pressure would cause a decrease in volume (P and V inversely related)
  • Hence, there will be a large number of moles of gaseous substance per unit volume
  • Hence, this can be undone by moving in a direction where pressure decreases or produces lesser number of moles per unit volume {Also moles and P are proportional if you want to write in short}
  • Here, the number of moles in products (2 < 4) hence, equilibrium will shift towards the direction of products – aka the forward direction
45
Q

Pressure change (le chatelier) on solids and liquids

A

Can be ignored because the volume of a solid / liquid is nearly independent of pressure

46
Q

Effect of pressure change
(C + CO2(g) –> 2CO(g))

A

When pressure is increased, the reaction goes in the reverse direction because the number of moles of gas increases in the forward direction

47
Q

Pressure change for no change in number of molecules

A

Pressure has no impact on equilibrium

48
Q

Decrease in pressure

A

Causes a shift in the direction of higher number of moles

49
Q

Explain using Kc and Qc for increase in pressure of:
CO(g) + 3H2 (g) –><– CH4 (g) + H2O (g)

A

When pressure is doubled:
Qc = (2[CH4])(2[H2O])/(2[CO])(2[H2])^3
= Kc / 4
Since Qc < Kc: reaction will move in forward direction

50
Q

**

Effect of change of temperature on QC and Kc

A

For temperature, Kc value changes and not the Qc value

51
Q

Equilibrium constant with temperature

A
  • According to Le - Chatelier’s Principle, if the temperature of the system at equilibrium is increased, the equilibrium will shift in the direction in which the added heat is absorbed.
  • Eq. constant for exothermic reaction (- delta H) decreases as temp increases
  • Eq. constant for endothermic reaction (+delta H) increases as temp increases
52
Q

Using example of N2 + 3H2 –><– 2NH3 explain effect of change of temperature

A
  • We know the forward reaction is exothermic while the backward reaction is endothermic
  • Hence, when heat is added to the system, it would change in the direction of the backward reaction
  • The backward reaction being endothermic, reaction will be favoured by increasing temperature as it tends to undo the effect of added heat
53
Q

Eq. constant with decrease in temp

A
  • A decrease in temp for exothermic reaction favours forward reaction
  • A decrease in temp for endothermic reaction favours backward reaction
54
Q

Change of solubility with temp

A
  • Solubility increases with increase in temp (endothermic reaction)
  • Solubility decreases with increase in temp (exothermic reaction)
55
Q

Effect of volume change on equilibrium

A

PV = constant
Increase in Volume = Decrease in P
hence it will be the exact opposite

56
Q

What does a catalyst do?

A
  • Increases the rate of chemical reaction by making available a new low energy pathway for the conversion of reactants to products
  • Increases the rate of forward and backward direction that pass through the same transition rate and does not affect equilibrium
  • Lowers the activation energy of forward and backward reaction by the same amount
57
Q

When is a catalyst of no use?

A

When K is an exceedingly small value

58
Q

Effect of addition of inert gas (constant pressure)

A

At constant pressure, the volume increases
Opposite of increase in pressure and favours the direction in which there is an increase in the number of moles of gases

59
Q

Effect of addition of an inert gas at constant volume

A

At constant volume, total pressure will increase
But, no change in concentrations of reactants and products –> hence no effect on equilibrium

60
Q

Conductance of electricity increases with increase in

A

concentration of common salt

61
Q

Electrolytes

A

An electrolyte is a substance that conducts electricity through the movement of ions, but not through the movement of electrons.

62
Q

Strong electrolytes vs Weak Electrolytes

A

Strong: On dissolution with water are ionized almost completely
Weak: Partially dissolved

63
Q

Why does NaCl only conduct in aqueous state?

A
  • NaCl is held together with strong electrostatic forces of attraction
  • When dissolved in water, a dielectric constant of water cuts down forces of attraction between the ions
64
Q

Ionic Equilibrium

A

Equilibrium established between the unionized molecules and the ions in solution of weak electrolytes

65
Q

Dissociation

A

Process of separation of ions already present in the solid state of solute when dissolved in water or a solvent

66
Q

Ionization

A

Process in which a neutral molecule which does not contain ions splits into charged ions when dissolved in water or a solvent

67
Q

Arrhenius concepts of bases

A

Substances that dissociates in aqeous solutions to give OH- ions

68
Q

Arrhenius concept of acids

A

Substances that dissociate in water to give H+ ions

69
Q

Relation between electrostatic forces and dielectric constant

A

Inversely proportional

70
Q

Strong acids vs Weak acids

A

Strong: Almost completely ionized in aqueous solution
Weak: Weakly ionized in aqueous solution

71
Q

Strong base vs Weak Base

A

Strong base: Almost completely ionized in aqueous solution
Weak base: Slightly ionized in aqueous solution

72
Q

Explain Hydronium ions

A
  • A bare proton of H+ is very reactive and cannot exist freely in aqueous solutions
  • Bonds to the oxygen atom of a solvent water molecule to give trigonal pyramidal hydronium ion
73
Q

Bronsted - Lowry Theory

A
  • Acid is a substance that is capable of donating a hydrogen ion H+ and bases are capable of accepting a hydrogen ion H+
  • Acids are proton donors
  • Bases are proton acceptors
74
Q

Amphoteric

A

Substances that behave both as an acid and a base

75
Q

Conjugate Acid - Base

A
  • A base forms a conjugate acid (as it gives it an extra proton)
  • An acid forms a conjugate base (as it removes an extra proton)
76
Q

Relative strengths of conjugate acid base

A

Acid depends upon the tendency to donate a proton and strength of a base depends upon its tendency to accept a proton

77
Q

Lewis acids and Lewis bases

A

Lewis Acid = Substance which can accept a pair of electrons
Lewis Base = Substance which can donate a pair of electrons

77
Q

Lewis Acids

A
  • Molecules in which central atom has an incomplete octet
  • Simple cations
  • Molecules with central atom having an empty d - orbital
  • Molecules in which multiple atoms of dissimilar electronegativities are joined by multiple bonds
77
Q

Relation between base and conjugate acid

A

Strong acid = Weak conjugate base
Strong base = Weak conjugate acid
Weak acid = Strong conjugate base
Weak base = Strong conjugate acid

77
Q

Lewis Bases

A
  • Neutral species having at least one lone pair of electrons
  • Negatively charged species of anions
78
Q

Ionic Product of Water

A

Dissociation constant is represented by the product of [OH-] * [H+] ions
Represented as Kw
Found to be 10^-14 M^2

79
Q

pH

A

The negative logarithm of the H3O+ ion concentration in moles per litre
pH = -log aH+ = - log {[H+] / mol L^-1}

80
Q

Degree of Dissociation

A

Fraction of the total number of molecules of an electrolyte which ionizes into ions

80
Q

Acid dissociation constant (Ka)

A

An acid dissociation constant is a quantitative measure of the strength of an acid in solution

80
Q

High value of Ka vs Low value of Ka

A

Higher value = Strong acid
As it dissociates more

80
Q

Ka value for weak acids

A

Ka = c (alpha)^2
/
(1 - alpha)

81
Q

NH3 conjugate acid and conjugate base

A

Conjugate acid: NH4 +
Conjugate base: NH2-

82
Q

Base ionization constant

A

Equilibrium constant for base ionization (Kb)

83
Q

[H2O]Keq value

A

10^-14 at 298K

83
Q

Acid Base Neutral

A

Neutral: [H+] = [OH-] = 10 ^ - 7
Acid: [H+] > [OH-] (> 10^-7)
Base: [H+] < [OH-] (< 10^-7)

84
Q

Ionic product of water

A

The autoionization of liquid water produces OH− and H3O+ ions. The equilibrium constant for this reaction is called the ion-product constant of liquid water (Kw) and is defined as Kw=[H3O+][OH−]. At 25 °C, Kw is 1.01×10−14; hence pH+pOH=pKw=14.00.

85
Q

How to do pH questions for strong acids or strong bases

A
  • They dissociate completely so final concentration for the acid is always 0
  • alpha = 1
  • Then just using molarity calculate the [H+] ions conc.
86
Q

pH +pOH =

A

14

87
Q

pH for acids with smaller concentrations

A

Consider the dissocation of the acid and the self ionization of water

88
Q

For pH of acids with smaller conc. why do we take ‘x’ while calculating ionization of water

A
  • Water dissociates less as we add more H+ from the acids due to Le Chatelier’s Principle
  • The concentration of OH- is x
  • The concentration of H+ is 10^-a + x because we have to consider both ways
89
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Chem - Gr11 (8 decks)

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