Redox
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Transcript of 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.