DAT chem - redox and electrochemistry

Reducing agent /reductant

the reactant that gets oxidized

oxidizing agent/ oxidant

The reactant that gets reduced

oxidation rules - uncharged atoms bound to themselves

oxidation number of 0

oxidation rues - monoatomic ions

oxidation number qual to the charge of the ion

Oxidation rules - nonmetals

O2 - always has an oxidation number of -2. except in H2O2, where it is one

halogens - typically always -1, unless bonded to hydrogen

hydrogen - usually +1, but -1 when bonded to metals

Oxidation rules - group 1 and 2 metals

Group 1 typically is always +1, and group 2 is typically always +2

Caza - oxidation rules

Cd - 2+

Ag +1

Zn 2+

Al 3+

how to balance redox reactions under acidic conditions

1. do half reactions

2. Balance non oxygen or hydrogen

3. balance Oxygen by adding H2O

4. balance Hydrogen by adding H+

5. add e-

6. balance e-s by multiplying

how to balance redox reactions under basic conditions

1. do half reactions

2. Balance non oxygen or hydrogen

3. balance Oxygen by adding H2O

4. balance Hydrogen by adding H+

5. add Oh- for each H+ added

6. Combine to form H2O

7. add e-s

8. balance e-s by multiplying

Battery

a reductant and an oxidant are connected via a wire, creating a current through the wire, the energy of that flow can be used to power devices

What charge is the anode

negative

What charge is the cathode

positive

Where is the reductant located

cathode

Where is the oxidant located

anode

What does the salt bridge do

It serves as a source of unreactive cations and ions To counterbalance charges in anode and cathode as they build up

What are the Energetics of a voltaic cell

The anode is at a higher energy level, and the cathode is at a lower energy level

IT IS SPONTANEOUS

What do emf and Ecell mean

The ability of a voltaic cell to provide energy

Whats the relationship betwen spontaneous reactions and Ecell

a spontaneous reaction = - delta G = positive Ecell

a nonspontaneous reaction = + delta G = negative Ecell

What type of ion flows towards the cathode

CATIONS (+)

ECELL CALCULATION

E REDUCTION + E OXIDATION = ECELL

YOU NEED TO MAXIMIZE THE ECELL TO BE AS POSITIVE AS POSSIBLE

Electrolytic cell

the opposite of a voltaic cell

oxidant into reductant powered by an outer electrical current

Whats the anode and cathode charge in an electrolytic cell

anode - Positive

Cathode - negative

Molten electrolysis

ELECTROLYTIC CELL

Like a galvanic cell, but with no salt bridge

There is a sea of K+ and I- ions,

1. A power source is attached to the cell, changing the cathode negative and the anode positive

2. Electrons still flow from anode to cathode, making the Anode more positive and the cathode more negative

3. anions then flow to the positive anode, being reduced

4. cations then flow to the negative cathode, being oxidized

aqueous electrolysis

like molten electrolysis,

but the addition of water also reduces H2+ into H2

What happens when you cause a reaction to move towards the products side

it will increase spontaneity therefore increasing Ecell

What happens when you cause a reaction to move towards the reactants side

it will decrease spontaneity, therfore decreasing E cell

Nernst equation

E cell = E naught cell - (0.0592/n) * log(Q)