Acids and Bases

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Acids
and
Bases
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Acid and Bases
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Acid and Bases
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Acid and Bases
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Some Household Acids and Bases
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Acids
Have a sour taste. Vinegar is a solution of
acetic acid. Citrus fruits contain citric acid.
Will react with certain metals to produce
hydrogen gas.
Will react with carbonates and bicarbonates to
produce carbon dioxide gas.
Bases
Have a bitter taste.
Feel slippery. Many soaps contain bases.
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Some Properties of Acids

• Produce H (as H3O) ions in water (the
  hydronium ion is a hydrogen ion attached to a
  water molecule)
• Taste sour
• Corrode metals
• Electrolytes
• React with bases to form a salt and water
• pH is less than 7
• Turns blue litmus paper to red (red acid)

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Some Properties of Bases

• Produce OH- ions in water
• Taste bitter, chalky
• Are electrolytes
• Feel soapy, slippery
• React with acids to form salts and water
• pH greater than 7
• Turns red litmus paper to blue Base Blue

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Some Common Bases

• NaOH sodium hydroxide lye
• KOH potassium hydroxide liquid soap
• Ba(OH)2 barium hydroxide stabilizer for
  plastics
• Mg(OH)2 magnesium hydroxide MOM Milk of
  magnesia
• Al(OH)3 aluminum hydroxide Maalox (antacid)

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Reactions of acids and bases

• HNO3 KOH -gt KNO3 H2O
• A reaction between an acid and a base is a type
  of double replacement reaction called
  neutralization.
• In a neutralization reaction, water and a salt
  are produced.

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Some Properties of Salts

• A salt is the combination of an anion (- ion) and
  a cation ( ion).
• Salts are products of the reaction between acids
  and bases.
• Solid salts are usually crystalline.
• If a salt dissolves in water, it usually breaks
  up into the ions that make up the salt.

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Strong Acids and Bases

• Strong acids are those that break apart
  (dissociate) completely in water.
• What does the diagram on the right show about how
  strong acids break apart?

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7 Strong Acids

• HNO3 - nitric acid HCl - hydrochloric
  acidHBr - hydrobromic acidHI - hydroiodic
  acid
• H2SO4- sulfuric acid
• HClO4 - perchloric acid HClO3 - chloric acid
  

• Strong acids are assumed to ionize completely
  (100)
• in water. They exist as H3O ions in water. This
  is known
• as the leveling effect.

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Strong Bases

• LiOH - lithium hydroxideNaOH - sodium
  hydroxideKOH - potassium hydroxideRbOH -
  rubidium hydroxideCsOH - cesium
  hydroxideBa(OH)2 - barium hydroxideSr(OH)2 -
  strontium hydroxideCa(OH)2 - calcium hydroxide

GROUP 1 hydroxides
Some GROUP 2 hydroxides

• In most cases, strong bases will also ionize
  completely
• in water.

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Weak Acids and Bases

• Some acids and bases ionize only slightly in
  water.
• These are considered weak.
• The most important weak base is ammonia.

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Balance of ions in acidic solutions

• Acidic Neutral
• Solution Solution

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ANIMATION LINKS

• Acid ionization equilibrium demo

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The pH scale is a way of expressing the strength
of acids and bases instead of using very small
numbers. It ranges from 0-14.Under 7 acid
7 neutralOver 7 base
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pH of Common Substances
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pH testing

• There are several ways to test pH
• Blue litmus paper (red acid)
• Red litmus paper (blue base)
• pH paper (multi-colored)
• pH meter (7 is neutral, lt7 acid, gt7 base)
• Universal indicator (multi-colored)
• Indicators like phenolphthalein
• Natural indicators like red cabbage, radishes

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Indicators
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Paper testing

• Paper tests like litmus paper and pH paper
• Put a stirring rod into the solution and stir.
• Take the stirring rod out, and place a drop of
  the solution from the end of the stirring rod
  onto a piece of the paper
• Read and record the color change. Note what the
  color indicates.
• You should only use a small portion of the paper.
  You can use one piece of paper for several tests.

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pH and Flowers

• For most big leaf hydrangeas, blue flowers will
  be produced in acidic soil (pH 5.5 and lower),
  whereas neutral to alkaline soils (pH 6.5 and
  higher) will usually produce pink flowers.
  Between pH 5.5 and pH 6.5, the flowers will be
  purple (see image at right) or a mixture of blue
  and pink flowers will be found on the same plant.

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Conjugate acid-base pairs

• Neutralization reaction example
• HCl HOH ? H3O Cl
• Notice that each pair (HCl and Cl as well as HOH
  and H3O differ by one hydrogen ion (H).
• These pairs are called conjugate pairs.
• Example HNO3 HOH ? H3O NO3
• What is the conjugate base to the acid HNO3? What
  is the conjugate acid to the base HOH? What are
  the pairs?

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WHAT IS A BUFFER?

• A buffer solution is one which resists changes in
  pH when small quantities of an acid or a base are
  added to it.
• How do buffer solutions work?
• A buffer solution has to contain things which
  will remove any hydrogen ions or hydroxide ions
  that you might add to it - otherwise the pH will
  change.
• buffer demo

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Definition of Acid Rain

• Precipitation that has a pH less than that of
  natural rainwater (which is about 5.6 due to
  dissolved carbon dioxide).
• It is formed when sulfur dioxides and nitrogen
  oxides (gases or fine particles in the
  atmosphere) combine with water vapor and
  precipitate as sulfuric acid or nitric acid in
  rain, snow, or fog.

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What Causes Acid Rain?

• Natural Sources
• -Emissions from volcanoes and from biological
  processes that occur on the land, in wetlands,
  and in the oceans contribute acid-producing gases
  to the atmosphere
• -Effects of acidic deposits have been detected
  in glacial ice thousands of years old in remote
  parts of the globe
• The principal cause of acid rain is from human
  sources
• -Industrial factories, power-generating plants
  and vehicles
• -Sulfur dioxide and oxides of
• nitrogen are released during
• the fuel burning process
• (i.e. combustion)

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How Does Acid Rain Form?
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Formation of Acid Rain

• When water vapor condenses, or as the rain falls,
  the gases and particles dissolve in the water to
  form sulfuric acid (H2SO4) and nitric acid
  (HNO3).
• While the air is cleansed of the pollutants in
  this way, it also causes precipitation to become
  acidic, forming acid rain.

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Formation of Acid Rain
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What Areas Are Most Affected?

• Canada -Water and soil systems lack natural
  alkalinity such as lime base and cannot
  neutralize acid
• Industrial acid rain is a substantial problem in
  China, Eastern Europe and Russia and areas
  down-wind from them.
• Acid rain from power plants in the Midwest United
  States has also harmed the forests of upstate New
  York and New England.
• NOTE This shows that the effects of acid rain
  can spread over a large area, far from the source
  of the pollution

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Effects of Acid Rain

• Harmful to aquatic life
• Increased acidity stops eggs of certain organisms
  (e.g. fish) from hatching
• Changes population ratios and affects the tissues
  of sensitive organisms
• Harmful to vegetation
• - Increased acidity in soil
• Removes nutrients from soil, slowing plant growth
• Dissolves toxins from soil, poisoning plants
• Creates brown spots in leaves of trees, impeding
  photosynthesis
• Allows pests to infect vegetation through broken
  leaves

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Effects of Acid Rain

• Harmful to buildings
• -Accelerates weathering in metal and stone
  structures, and roads
• -Ex Parthenon in Athens, Greece Taj Mahal in
  Agra, India
• Harmful to human health
• Respiratory problems, asthma, dry coughs,
  headaches and throat irritations
• Leeching of toxins from the soil by acid rain can
  be absorbed by plants and animals. When consumed,
  these toxins affect humans.

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Effects of Acid Rain
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What can we do?

• Reduce amount of sulfur dioxide and oxides of
  nitrogen released into the atmosphere
• Use less energy (less fuel burned)
• Use cleaner fuels that contain less sulfur
• Remove oxides of sulfur and oxides of nitrogen
  before releasing
• Use other sources of energy such as solar,
  geothermal, nuclear, wind,
• etc (more expensive)
• Liming powdered limestone
• or limewater added to water
• and soil to neutralize acid
• (expensive)

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CAPT Activity Brownfields

• Link to North Haven Pharmacia and Upjohn LLC
  site
• http//www.upjohnnorthhaven.com/background.php