Chapter 10

Question 1

Equilibrium

Answer 1

A state at which both the forward and reverse reactions occur at the same constant rate. At equilibrium, the overall concentration of reactants and products remain the same, but at the molecular level, they are continually interconverting. because the forward and reverse processes balance one another perfectly, we don’t observe any net change in concentrations. This only occurs for closed systems
*pg202

Question 2

Equilibrium constant

Answer 2

Each reaction will tend towards its own equilibrium and, for a given temperature, will have an equilibrium constant, k_eq.
This expression is product concentrations to the power of their coefficients over the reactant concentrations to the power of their coefficients:
aA +bB cC + dD
K_eq = [C]^c [D]^d / [A]^a [B]^b
Known as the mass-action ratio
k_a is for acids, k_b is for bases, and k_sp is for solubility product.
The value for K_eq for a given reaction is a constant at a given temperature.
*pg202

Question 3

What can and cannot be included in the equilibrium constant

Answer 3

Solids and pure liquids are not included.
we’re also allowed to omit solvents in dilute solutions bc the solvents are in vast excess and their conc do not change.
Aqueous dissolved particles are included
if the reaction is gas, we can use the partial pressure of each gas as its concentration, the constant using pressures will be different than using concentrations, we call it K_p
*pg203

Question 4

what does the value of K_eq tell you

Answer 4

K_eq < 1 : reaction favours the reactants (more reactants than products0
K_eq = 1 : reaction has roughly equal amounts of reactants and products
K_eq > 1 : Reaction favours the products (more products)
*pg203

Question 5

Reaction Quotient (Q)

Answer 5

The same thing as equilibrium constant but when the reaction is not at equilibrium. The expression is written the exact same way as the equilibrium constant. If you calculated this when the reaction was at equil it would equal to K_eq
*pg205

Question 6

Comparing Q to K_eq

Answer 6

Q < K_eq : the reaction will proceed forward (to inc the conc of products)
Q = K_eq: the reaction is at equil (the preferable situation)
Q > K_eq : the reaction will proceed in the reverse direction (to inc the reactants)

the goal is to reach Q=K_eq
*pg205/206

Question 7

Le Chatelier’s Principle

Answer 7

States that a system at equilibrium will try to neutralize any imposed change (or stress) in order to reestablish equil
in an equation: A + 3B 2C +heat
adding C: favours the reverse reaction, the system will shift to the left
Removing C: favours the forward reaction. The system will shift to the right
Adding B: the forward reaction will be favoured, shifts to the right.
Removing A: the reverse reaction is favoured, shifts to the left
Changing volume: if volume is reduced it favours the side with the smaller # of moles, and vice versa.
adding heat: lowering the temp favours the exo reaction, and raising the temp favours the endo reaction
Adding an inert gas: they don’t participate in any reaction that has constant volume, if it’s added to constant pressure, it increases its volume and follows the volume rule.
Adding a catalyst: no effect
*pg207/208/209

Question 8

Solutions

Answer 8

A solution forms when one substance dissolves into another, forming a homogenous mixture.
(pg211

Question 9

Dissolution

Answer 9

The process of dissolving.

*pg211

Question 10

Solute vs solvent

Answer 10

Solute: a substance present in a smaller proportion

solvent: a substance present in a relatively larger proportion
* PG211

Question 11

Solvation

Answer 11

the process that occurs when the solvent molecules surround the solute molecules.
This is known as hydration if the solvent is water
*pg211

Question 12

Aqueous solution

Answer 12

When solution has water as the solvent.

*pg211

Question 13

which solutes are soluble in which solvents

Answer 13

Like dissolves like. Solutes dissolve best in solvents where the intermolecular forces being broken in the solute are being replaced by equal or stronger intermolecular forces bw the solute and the solvent.
*pg211

Question 14

Ions being dissolved

Answer 14

When ionic substances dissolve, they dissociate into ions. Free ions in a solution are called electrolytes bc the solution can conduct electricity.
*pg211

Question 15

Strong vs week electrolytes

Answer 15

Solutes that dissociate completely are called strong electrolytes (like ionic substances), these are better conductors of electrcity.
And those that remain ion-paired to some extent are called weak electrolytes.
*pg211

Question 16

Nonelectrolytes

Answer 16

Covalent compounds that don’t dissociate into ions.

*pg211

Question 17

Van’t Hoff (or ionizability) factor (i)

Answer 17

Tells us how many ions one unit of substance will produce in a solution.
For example: C6H12O6 is non ionic so it doesn’t dissociate so i=1, NaCl dissociates into Na+ and Cl- so i = 2, CaCl2 dissociates into Ca2+ and 2 Cl- so i = 3
*pg211

Question 18

Concentrated Vs dilute

Answer 18

Concentrated solution has a greater amount of solute per unit volume than a solution that is dilute, which has more solvent than solute.
*pg212

Question 19

Saturated solution

Answer 19

is one in which no more solute will dissolve. one that has reached the molar solubility, and the reverse process of dissolution, called precipitation, occurs at the same rate as dissolving. In this case both the solid form and dissolved form of the solute are said to be in dynamic equilibrium.
*pg212

Question 20

Solubility

Answer 20

Refers to the amount of solute that will saturate a particular solvent. Solubility is specific for the type of solute and solvent. Two sets of rules: one that talk about the general solubility of solids and gases in liquids as a function of temp and pressure (phase solubility rules) and ones that talk about solubility of salts in water (Salt solubility rules)
*pg213

Question 21

Phase solubility rules (3)

Answer 21

1. The solubility of solids in liquids tend to inc with inc temp
2. The solubility of gases in liquids tend to dec with inc temp
3. The solubility of gases in liquids tends to inc with inc pressure
   these are 95% reliable
   *pg213

Question 22

Salt solubility rules (3)

Answer 22

1. All Group I (Li+, Na+, K+, Rb+, Cs+) and ammonium (NH4+) salts are soluble
2. All nitrate (NO3-), Perchlorate (ClO4-), and acetate (C2H3O2-) salts are soluble
3. All silver (Ag+), lead (Pb2+/4+), and mercury (Hg2 2+/ Hg2+) salts are insoluble, except for their nitrates, perchlorates, and acetates.
   * pg213

Question 23

Solubility Product Constant

Answer 23

Tells us the extent to which a salt will dissolve in water. It is another equil constant, one in which the reactants and products are just undissolved and dissolved salts. Do not add solids and liquids in this expression
*pg214

Question 24

Molar Solubility

Answer 24

The number of moles that salt that will saturate a liter of water.
*pg215

Question 25

Ion product, Q_sp (how is it diff from K_sp)

Answer 25

The reaction quotient for a solubility reaction. That is which K_sp is equal to the product of ion concentrations if the ions in solution when the solution is saturated (at equil), the ion. product (Q_sp) is exactly the same form as K_sp but the concentrations don’t have to be at equil. It helps us make predictions about what the reaction will do:
Q_sp < K_sp : more salt can be dissolved (forward reaction is favoured)
Q_sp = K_sp : Solution is saturated
Q_so > K_sp excess salt will precipitate (reverse reaction is favoured)
*pg216

Question 26

Common ion effect

Answer 26

When a compound is added to a solution that has an ion that is the same as the existing solution (known as common ion) it will follow Le Chatelier’s principle. For example adding NaOH to Mg(OH)2 where OH is the common ion, it will increase the OH (reactant) in the MgOH2 and favour the product side.
*pg216

Question 27

Complex Ions

Answer 27

Consist of metallic ions surrounded by generally 2, 4, or 6 ligands, also known as lewis base. They may have extremely different solubility products than the “naked” hydrated metal ions. Therfore the addition of ligands may substantially alter the solubility of simple metal salts.
*pg217

Question 28

Gibbs free energy equation with Q and K_eq

Answer 28

ΔG = ΔGº +RT lnQ
ΔGº = -RT lnK_eq
*pg218

Question 29

ΔG vs ΔGº

Answer 29

ΔG is a statement of spontaneity of a reaction in one direction or another. This changes the temp, pressure, and set of conc with changing reaction composition until it reaches 0.
ΔGº is, as seen in its relation to K_eq, a statement of the relative proportions of products and reactants present at equil. The standard state of ΔGº for a reaction only describes a reaction at one specific temp, pressure, and set of concentration.
*pg219

Question 30

Comparison of ΔGº and K_eq

Answer 30

ΔGº < 0 ; K_eq > 1 : Products are favoured at equil
ΔGº = 0 ; K_eq = 1 : Products and reactants are present in roughly equal amounts at equil
ΔGº > 0 ; K_eq < 1 : reactants are favoured at equil.
*pg219