Chapter 11 - RedOx, Batteries, Oxidation and Combustion

electrochemistry includes

fuel cells, batteries

oxygen includes

corrosion, corruption

Redox is a type of reaction that

involves reduction and oxidation

Reduction is the process by which

one reactant gains one or more electrons

Oxidation is the process by which one

reactant loses one or more electrons

LEO the lion says GER

Loss of Electrons is Oxidation; Gain of Electrons is Reduction

OIL RIG

Oxidation is Loss of Electrons; Reduction is Gain of Electrons

When something becomes oxidized the

element/molecule will become more positive

When an element / molecule becomes reduced it

will become more negative

The formation of NaCl from sodium, metal, and chlorine gas is as follows:

2Na(s) + Cl2(g) > 2NaCl(s)

To follow what really happens to the individual electrons we

need to look at the reaction of each element by itself

he Na reaction is the oxidation reaction in which Na gives up electrons to reduce Cl, Thus

Na is the reducing agent (provides the electrons needed to reduce the other element)

The Cl reaction is the reduction reaction in which Cl accepts the electrons that Na gave up, thus

Cl is called the oxidizing agent cause it allowed the Na to become oxidized

When finding what has been oxidized or reduced you need

to know the current charge on all of the elements in the compounds

lone elements like Na(s)

start out neutrala

all nonmetals have a

specific charge

group 1, 2, and 13 metals

have a set charge

Oxidation numbers are a way to track changes

in charge in molecules that are neutral.

The oxidation number or oxidation state of an element

in a compound can vary from the predicted charge.

Basically, the most electronegative element in a compound will be given its standard ionic charge. The rest of the elements

in the covalent molecule will be given positive values until the whole molecule is neutral again

redox reactions have many

every day applications

In this modern age electricity powers

the majority of our daily conveniences

redox reactions involve the transfer

of electrons (electricity)

what is an electrode

some material that conducts electrons into or out of a medium (solution)

what is a cathode

the electrode where reduction takes place (accepts electrons)

what is an anode

the electrode where oxidation takes place (loses electrons)

if you separate the two reactions you can

create a flow of electron

electrons flow through the wire that connects

these two electrodes and produces a current

the anode builds up positive charges which

attract the electronst

the cathode builds up negative charges which

repels the electrons

a salt bridge supplies each solution

with the appropriate counter charge

batteries use this separation of solutions to provide

power to all of our portable electronic devices

what happens in a rechargable battery?

As with all batteries the solutions in each cell of the battery eventually run out of materials to oxidize/reduce

a rechargeable battery will use electrons to run the process

in reverse regenerating the oxidizable material

a fuel cell is a battery run by

the oxidization of gas (H2)

unlike most fuels the oxidation of hydrogen gas provides a substantial

supply of energy with no pollutants (the product of the reaction is pure water vapor)

oxygen tends to be

an oxidizer (oxidizing agent)

oxygen can cause

corrosion and combustion

We all know iron rusts, the reaction is: 4 Fe + 3 O2+ 3 H2O → 2 Fe2 O3 * 3 H2 O. What actually happens on

the metal (Fe) surface is the water droplet sets up an anode and cathode

as iron oxide forms it is water soluble and thus dissolves into

the water creating holes in the iron

since iron rusts, it needs to be

protected from oxygen in order to remain solid

galvanization is the process of

of coating a metal like iron with another metal that more readily oxidzes like zinc

zinc oxide is

insoluble in water

electroplating is covering oxidizable metals with

corrosion resistant metals like platinum, gold, or chromium

cathodic protection - using a more

oxidizable material to keep another material from oxidizing

ships are constantly in

contact with water and oxygen

ships are also too large to

coat in a protective material or a corrosion resistant metal

electrons will always flow from the

most easily oxidized material first

zinc oxidizes more readily

than iron

combustion reactions involve a

nonmetallic material and oxygen

combustion reactions are generally

exothermic

examples of exothermic combusions

gas burning stoves and water heaters