Electrochemistry

Question 1

Types of electrochemical cells

Galvanic (aka voltaic)

Answer 1

Reactions: Spontaneous reactions

Cell potential (emf): (+)

∆G: (-)

Anode/cathode: Anode (-), Cathode (+)

Question 2

Types of electrochemical cells

Electrolytic

Answer 2

Reactions: Non-spontaneous reactions

Cell potential (emf): (-)

∆G: (+)

Anode/cathode: Anode (+), Cathode (-)

Question 3

Types of electrochemical cells

Concentration

Answer 3

Reactions: Spontaneous reactions

Cell potential (emf): 0

∆G: 0

Anode/cathode: Both electrodes same material. Movement driven by concentration gradient

Question 4

Types of electrochemical cells

Compare and contrast Galvanic (aka voltaic) vs Electrolytic vs concentration

Answer 4

Question 5

Potentials

Cell potential (aka electromotive force)

Answer 5

Question 6

Potentials

Nernst equation

Answer 6

Question 7

Potentials

Gibbs free energy in cells

Answer 7

Question 8

Redox

Change in electrons

Answer 8

Mnemonic: LEO the lion says GER.
Lose Electron Oxidation, Gain Electron Reduction.

Question 9

Redox

Change in H and O

Answer 9

Reduction: Gain H, lose O.

Oxidation: Gain O, lose H.

Question 10

Redox

Change in oxidation numbers

Answer 10

Reduction: oxidation number decreases.

Oxidation: oxidation number increases.

Question 11

Redox

Agents

Answer 11

A reducing agent helps another compound get reduced. Therefore the agent itself will become oxidized and donate electrons. And vice versa.

Question 12

Oxidation numbers

Definition

Answer 12

Defined as the charge of an atom if all bonds were ionic bonds.

Question 13

Oxidation number

Rules

Answer 13

1. If it’s a single atom, oxidation number is equal to charge (or equal to 0 if atom in elemental state). If in a compound, proceed.
2. Assign +1 to H except assign -1 if it exists as H- ion.
3. Assign -2 to O except assign -1 if it exists as a peroxide.
4. Assign -1 to a CN group.
5. Assign +1 to group 1 metals or +2 to group 2 metals.
6. The sum of oxidation numbers in a compound has to equal its charge, so assign missing values to make this true.

Question 14

Electrochemical cell structure

Anode and cathode

Answer 14

Mnemonic: AN OX and RED CAT
Anode: site of oxidation, will attract anions
Cathode: site of reduction, will attract cations

Question 15

Electrochemical cell structure

Flow

Answer 15

Electrons flow from anode to cathode for both galvanic and electrolytic cells