Redox

Oxidation-Reduction

page 145 top left, Lab Manual, 6th Ed.

Oxidation-Reduction

p.145 top left

Loss of Electrons is Oxidation (LEO),

Gain of Electrons is Reduction (GER)

page 145 middle down

Baseball analogy

Loss or gain of an electron makes a difference.

Left has Copper(II) chloride (aqua-blue color),

right has Copper(I) chloride (green solid).

Vanadium was named for the beauty of the colors in V’s several oxidation states.

Chromium is named forthe bright colors of its compounds (Greek chroma = color)

Colors of manganese compoundsMnO (black, left), Mn3O4 (gray,

top),Mn2O3 (green, bottom), MnO2

(red-brown)

Ethanol Breathalyzer

Oxidizing Agent & Reducing Agent

p.145 bottom left

Zinc in Copper sulfate solution

p.145bottom right

Activity series

page 149

p.146 top, 6th Ed.

Life, Nitrogenase, & Antiseptics

page 146, 6th Ed.

SCUBA Diving shows the gases of animal life

as divers must bring tanks of oxygen and carbon dioxide bubbles

are released.

Nodules on root hairs of legume plants (peas

& beans)formed by nitrogenase

bacteria

• Nitrogenase catalyzes the reaction of dinitrogen from the air to produce ammonia. (at room temp. and pressure!)

Haber Process: Making Ammonia from Nitrogen and Hydrogen

Decomposition of Compounds with air (or without)

page 147 top, 6th Ed.

Antiseptics (Disinfectants)

page 146 bottom (#4), 6th Ed.

Water treatment and purification

page 147, #6, 6th Ed.

In 1992, Greenpeace and the Sierra Club called for a ban

on all chlorine.

Uses of chlorine in 2002

in 1993

Chlorine is used for

Swimming pool disinfection• Sodium hypochlorite (NaOCl) reacts with water to slowly release elemental Cl2

• Chlorine (Cl2) slowly evaporates from the pool, so more must be added periodically.

• Mixing too much or incorrect use can cause fatal accidents.

Bleach reacts with acids or with bases to produce

poisonous gases.

Bleach effect on colors

• Bleach reacts with carbon-carbon double bonds in the colored pigment and decolorizes (bleaches) it.

• Green felt in water and in Hydrogen peroxide

Bleach effect on chemical structure

Stain removers, cleansers, & bleaches

page 148 top left, 6th Ed.

Rust stains in sink, toilet bowl, and bath

due to soluble iron ions in the water

Cleansers often have strong bases & oxidizers

and are frequently corrosive and caustic.

Some jobs require acid cleansers, too.

Hydrogen peroxide

• 3% disinfects cuts• 6% bleaches hair• 30% bleaches skin to white on contact (very corrosive)

• 98% hydrogen peroxide is used as oxidizer for rocket fuel.

Antioxidants

Atmospheres of Planets in our Solar System

Air pollutants are usually oxidized molecules

A reaction like that of B&W film photography:

Silver chloride white powder with a paper clip on top is exposed to a bright light, which darkens the

AgCl as free Ag is formed

B&W Film Photography

Photography has many redox

reactions(Color

photography shown here)

Three invisible gases are

involved in a fire: oxygen in, carbon dioxide out, and water vapor out.Plants are rich in

potassium, and so are the ashes (potash is the source & etymology for potassium).

Combustiontriangle(here in Spanish)

• Three requirements for combustion:

• Fuel (gaseous fuel)

• Oxygen (or other oxidizer)

• Ignition (heat, spark, or match)

To extinguish a fire, one must remove

one (or more) of the three requirements• Remove the fuel

(spread it out, cover it).

• Remove the oxygen (cover the fire with a solid lid, smother it with carbon dioxide or water).

• Remove the heat (soak it with water, spread it out)

• Remove free radicals (radicals are needed for flames) [4th requirement would use a flame tetrahedron]

Fire extinguisher

• Sign for extinguisher location:

Fire suppression using Halons at an airport

Match for

Ignition

Phosphorus, Matches

Candle

• Wax melts• Liquid wax moves up in wick by capillary action.

• Gaseous wax burns when it reaches ignition temperature.

Oxygen

Steel wool in air & O2• Steel wool glows red-hot with a small flame in air.

• That glowing steel wool bursts into a larger flame in pure oxygen.

• (in German: reiner Sauerstoff)

Fuels burn faster and hotter in 100% oxygen than

in air (20% O2)Blowtorch flame

Can melt through metals with an acetylene (& 100% oxygen) torch

Apollo 1 accident while training on launching pad

100% oxygen was used within the capsule.

A fire started with seat materials that would not burn in 20% oxygen.

Astronauts White, Grissom, and Chaffee died.

Liquid oxygen

• Fuels burn faster in pure (100%) oxygen than in air (20% O2)

• Fuels burn even faster in liquid oxygen.

• See video of charcoal lighting at Purdue and video of diamond burning in liquid O2

Space Shuttle Challenger accident, Jan. 28, 1986

Chlorine, Bromine, & Iodine

Halogens in water & dense organic solvent

Chlorine water reduces bromide to bromine & iodide to iodine

Candle burns in chlorine

gas

• Candle continues burning until chlorine is used up.

• The products are mostly solids (in comparison to the gases of a candle in air), so the smoke is much thicker.

Hydrogen burns

in bromine vapor

Spontaneous combustion was starting in this stack of fiber boards. When smoke was detected, the stack was cut open to show the burned area. The stack insulates,

holding in any heat generated by oxidation or pyrolysis. Rags used in linseed oil frequently combust spontaneously (i.e.,

without ignition).

Spontaneous Human Combustion cannot occur.

Charles Dickens’ Bleak House (1853) describes a spontaneous human

combustion, which Dickens believed could occur.

Hypergolic fuels need no

ignition• Rocket fuels have no need for spark plugs or other ignition source.

• These fuels and their oxidizers are so potent that they react on mixing and start their own flame (these are called hypergolic).

• A liquid fuel rocket is shown at left.

Ignition

Explosives: Gunpowder

Gunpowder Ingredients: Charcoal, Sulfur

& Nitre (Potassium Nitrate)

Fireworks

Firecracker

• Usually made of black powder (gunpowder).

• Charcoal, sulfur, and potassium nitrate or potassium chlorate.

Hazard diamond placards

Texas City Explosion, April 16, 1947

Ammonium nitrate fertilizer on ship Grand Camp

Oklahoma City bombing, April

19, 1995• Timothy Mc Veigh, trained by U.S. Army in explosives use and preparation.

• Used Ammonium nitrate fertilizer and fuel oil, ignited by fuse and detonators.

September 11, 2001

• BLEVE• 9/11/2001

Thermite reaction: Rust and Dust (Al)

used to weld rails and in incendiary bombs

Thermite reaction

Incendiary materials:Mg, thermite, white Pin incendiary bombs of WWIIDresden, Hamburg, etc.