Chem 1022 Midterm Iii Material - Electrochemistry, Electrolysis, And Ionic Solubility

Front 1

Solubility (definition):

Back 1

The maximum amount of a solid that can dissolve in a liquid at a given temperature at equilibrium (in moles per liter).

Front 2

What determines solubility?

Back 2

- the identity of the solute
- the identity of the solvent
- temperature

Front 3

Molar solubility (definition):

Back 3

The maximum amount of moles of a salt that can dissolve per liter solution at equilibrium (in moles per liter)

Front 4

Relationship between Qsp & Ksp:

Back 4

- Qsp = Ksp: everything is dissolved, solution will be saturated
- Qsp < Ksp: everything will dissolve, a non-saturated solution
- Qsp > Ksp: precipitate remains, solution will be saturated

Front 5

Common Ion Effect (definition):

Back 5

For a weakly soluble salt, the solubility of the ionic compound will decrease when a common ion is added to the solution.

Front 6

What is the effect of pH on the solubility of a slightly soluble ionic compound?

Back 6

- By lowering the pH (adding hydronium ions), moving the equilibrium "to the left" and favoring the increase of reactants
- By increasing the pH (decreasing hydronium ions), moving the equilibrium "to the right" and favoring an increase in product

Front 7

First Law of Thermodynamics (definition):

Back 7

The total energy and the total entropy (mass-energy sum) of the universe is constant; explains that the addition of 2+ reactants will react by themselves and require no external influence (input of energy).

Front 8

Suniverse =

Back 8

System + Ssurroundings

Front 9

Exothermic process (definition):

Back 9

A reaction that produces heat (heat is a product). ΔH < 0

Front 10

Endothermic process (definition):

Back 10

A reaction that requires heat to occur (heat is a reactant). ΔH > 0

Front 11

Does the classification of a reaction as an exo-/endothermic process solely determine the reaction's spontaneity?

Back 11

No- the disorder of the system (entropy) does.

Front 12

Entropy (definition):

Back 12

A quantitative measure of the number of ways in which a substance can distribute its energy among its quantum states. Denoted as "S" in units of joules/Kelvin.

Front 13

The types of quantum states (4):

Back 13

- electronic
- vibrational
- rotational
- translational

Front 14

Second Law of Thermodynamics (definition):

Back 14

A process is spontaneous if the entropy of the universe is increasing. As ΔSuniverse is constantly increasing, Sfinal-Sinitial > 0 for a spontaneous process.

Front 15

The relative amount of entropy in the three phases:

Back 15

Ssolid < Sliquid < Sgas
(*always true*)

Front 16

What influences entropy (3)?

Back 16

- temperature
- phase
- amount

Front 17

ΔSsystem =

Back 17

Sproducts - Sreactants

Front 18

Gibb's Free Energy (defines):

Back 18

Whether or not a reaction is spontaneous at a given temperature and pressure. Denoted as "ΔG".

Front 19

Gibb's Free Energy (equation):

Back 19

ΔG = ΔH - TΔS

Front 20

Relation between ΔG and a reaction's spontaneity:

Back 20

- ΔG < 0, a reaction is spontaneous.
- ΔG > 0, a reaction is not spontaneous and will not occur.
- ΔG = 0, the reaction is at equilibrium

Front 21

Relationship between entropy, enthalpy, and Gibb's Free Energy for an exothermic process:

Back 21

- If ΔH < 0 and ΔS > 0, then ΔG < 0 and the process will occur at every temperature.
- If ΔH < 0 and ΔS < 0, then at high temperatures ΔG > 0 and at low temperatures ΔG < 0 (spontaneous).

Front 22

Relationship between entropy, enthalpy, and Gibb's Free Energy for an endothermic process:

Back 22

- If ΔH > 0 and ΔS < 0, then ΔG > 0 and will never occur regardless of temperature.
- If ΔH > 0 and ΔS > 0, then at high temperatures ΔG < 0 (spontaneous) and at low temperatures ΔG > 0.

Front 23

The two methods to determine ΔG:

Back 23

- Using the change in entropy (ΔH°) and enthalpy (ΔS°)
- (only under standard pressure) Using the product's standard molar free energy of formation (ΔGf°), as well as those of the reactants.

Front 24

Q (definition):

Back 24

The reaction quotient, dependent on the pressure that exists in reality.

Front 25

Relationship between the equilibrium constant K, the reaction quotient Q, and Gibb's Free Energy ΔG.

Back 25

- Q < K, the equilibrium "shifts to the right", ΔG < 0 (is spontaneous)
- Q = K, the equilibrium does hot shift, ΔG = 0
- Q > L, the equilibrium "shifts to the left", ΔG > 0 (reverse reaction is spontaneous)

Front 26

ΔG° =

Back 26

- RT*ln(k)

Where:
- R is the ideal gas law constant (8.314 J/mol*K)
- T is temperature in degree K
- K is the equilibrium constant

Front 27

(non-standard conditions) ΔG =

Back 27

ΔG° + RT*lnQ
or
RT*ln(Q/K)

Front 28

The relationship of ΔG to work:

Back 28

- ΔG < 0, the reaction is spontaneous and does/creates work. The value of ΔG is the maximum amount of work you can get out of a system.
- ΔG > 0, the reaction is not spontaneous as a forward reaction, and the work is done by the system. ΔG is the amount of work needed to be added to the system for the reaction to occur.

Front 29

General redox definitions:

Back 29

- Oxidation = loss of electrons
- Reduction = gain of electrons
- Oxidizing Agent = species that does the oxidizing (itself reduced)
- Reducing Agent = species that does the reducing (itself oxidized)

Front 30

Oxidation number (definition):

Back 30

The charge an atom would have if the electrons were not shared but were transferred completely to the most electromagnetic atom.

Front 31

Photovoltaic (Galvanic) Cell (definition):

Back 31

An electrochemical cell which produces electrical energy directly from a spontaneous redox reaction.

Front 32

Anode and Cathode (definition):

Back 32

The anode is the electrode at which oxidation takes place, the cathode, reduction.

Front 33

Cell potential (definition):

Back 33

The electrochemical difference between the anode and the cathode, denoted as "Ecell", in units volts.

Front 34

What's a joule?

Back 34

The unit of electrical work: 1 Joule = 1 Volt x 1 Coulomb

Front 35

What determines the cell potential (Ecell)?

Back 35

- composition of the half cells
- temperature
- concentration of ions in solution (molarity)

Front 36

Standard Electrode Potential (definition):

Back 36

The voltage of a half cell measured under standard conditions with respect to the standard hydrogen electrode (SHE), denoted as E°
- the higher the E°, the better an oxidizing agent
- the lower the E°, the better a reducing agent

Front 37

The relationship between E°reduction and E°oxidation for a half cell:

Back 37

E°reduction = -E°oxidation

Front 38

E°cell =

Back 38

E°cathode - E°anode

Front 39

Relationship between Ecell and ΔG:

Back 39

- If ΔG = 0, then Ecell = 0, and the reaction has no forward drive (a dead battery)
- If ΔG < 0, then Ecell > 0, and the reaction is spontaneous to the right (working battery)
- If ΔG > 0, then Ecell < 0, and the reaction is not spontaneous and requires work to occur

Front 40

Relationship between E° and the equilibrium constant K.

Back 40

(ok)

Front 41

Particular uses of a Galvanic cell:

Back 41

To measure extremely small/low concentrations of a solution that would be nearly impossible otherwise, or to determine the equilibrium constant Ksp.

Front 42

Fuel (Electrolytic) Cell (definition):

Back 42

Are voltaic cells for which the reactants are continually supplied, using combustion reactions to produce electricity (however the fuel does not burn).

Front 43

Electrolysis (definition):

Back 43

The method of using an electrical current to drive an otherwise non-spontaneous reaction. Measured via determining the measure of electron flow, denoted as "I" in units of amperes (A), the charge, denoted as "q" in units Coulombs (C).

Front 44

Faraday's Constant (definition):

Back 44

Is the magnitude of electric charge per mol of electrons, 9.65E4 C/mol*electrons.

Front 45

Avogadro's Number (definition):

Back 45

The number of number of electrons in a mole, 6.023E23.