Chem Unit 3 Electrochemistry

What does the faraday constant represent?

Represents # of coulombs of charge crried by 1 mol of e^-

F is

faraday constant of 10^5 C/mol

C/mol

coloumbs per mol

Formula: if given temp, E of cell and n

E°cell = (RT/nF) lnK

R is

8.134

How to undo ln

use e

Formula: if given time in minutes and A to find C

change min to sec, Q=i*t

As the concentration of reactants decreases in a galvanic cell, the magnitude of E°(cell) will

stay the same

To protect a metal, you need …

a more reactive metal

A non-rechargeable battery

primary

Reversible/reusable battery

secondary

To be a sacrificial anode

new metal must be more easily oxidized (lesser E° potential)

Cathode is side

where electrons are gained (red cat)

Anode is side

where electrons are lost (an ox)

Atom economy

Synthetic methods designed to maximize using all materials in process into the final product

Atom economy formula

AE = MW of used products/MW of all reactants * 100%

High atom economies

desirable

Low atom economies

non-desirable

pH is directly correlated with

H⁺

Nitrogen oxidation numbers

-3 to 5⁺

Nitrogen found in

explosives, fertilizer, and laughing gas

Phosphorus found in

fertilizers, soap, toothpaste

Phosphorus comes from

calcium phosphate rocks using wet method

H2SO4 used to

extract phosphorus from rocks and production of paper

Halides have

small radii, high ionization energy, high electronegativity, and form -1 anions

Halides oxides and hydrides are

acidic

Floruide found in

tooth inserts to prevent decay

Chloride found in

PVC tubing, sanitation, disinfection

Chloride is … agent

strong oxidizing agen

Noble gases uses

cryogens (He), inert gases (Ar), and lights (Ne).

Claus and Contact processes combine to produce

H2SO4 through a redox rxns

Claus

two-step oxidation produces elemental sulfur from H2S, found in methane.

Contact

four-step oxidation process produces H2SO4 from elemental S

Most manufactured chemical in the world.

H2SO4

About half of all sulfuric acid is used to

solubilize phosphate in rocks by the wet method

Finding oxidation in multiples

do not multiply

Free elements have an oxidation #

0

Hydrogen oxi #

+1

Individual ion oxi #

chage

Group 1

alkali

Group 1 oxi #

+1

Oxygen oxi #

-2

Which rule comes first H or O

H

Oxi # typically asisgned by

group on periodic table

Oxidation is

loss of electrons

Reduction is

gain of electrons

Oxidizinng agent is

being reduced, causes oxidation of OTHER species

Reduction agent is

being oxidized, causes reduction of OTHER species

Moving up reduction table, species are easier to … and are

reduce, strong oxidizing agents

Moving down reduction table, species are easier to … and are

oxidize, strong reducing agents

Top of table is

part of half-cell with largest positive reduction potential

Bottom of table is

part of half-cell with largest negative reduction potential

Battery delta G

negative

Battery K

>1

Battery reduction site

cathode

Electrolytic delta G

positive

Battery oxidation site

anode

Electrolytic oxidation site

anode

Electrolytic reduction site

cathode

Electrolytic e- flow

anode to cathode

Battery e- flow

anode to cathode

Battery cathode

positive

Battery anode

negative

Electrolyte cathode

negative

Electrolyte anode

positive

Electrons always flow

anode to cathode

Both cathodes and anodes are

solid

Very left side of shorthand cell notation

electrode

Electrodes are

anodes and cathodes

|| represents

salt bridge

Left side of salt bridge

anode

Right side of salt bridge

cathode

Oxidation occurs at

anode, right

Reduction occurs

cathode, left

Inert platinum

doesn’t participate in redox

More positive a E red

easier to reduce

More negative a E red

easier to oxidize

More positive a E ox

easier to oxidize

DFinding oxidation potential

flip sign in table

cations are

reduced

Anions are

oxidized

Standard hydrogen electrode at

0.0V

Potentials for ionic species measured at

1 M

Reference half reaction is at pH

0

Standard conditions for half reactions

1 M, 1 atm, and 298K

Q =

right/left, cathode/anode

Q>1

more products

Q < 1

more reactants

Q = 1

equal ratio of products/reactants

Q = K

system at equilibrium

Equilibrium is a

dead battery

E cell > E of cell

more reactants than products

E cell < E of cell

less reactants than products

E = E of cell

equal products and reactants

E = 0

equilibrium

New battery conditions

Q < 1

If given cell and 2 half reactions use … formula

E of cell, find Q (right/left), find E

Given i & t, find amount of material used/formed

i*t*F*MW*(1/#mol e⁻)

Rust made by

oxidation of iron in air and water