11

22

Acid and BasesAcid and Bases

33

Acid and BasesAcid and Bases

44

Acid and BasesAcid and Bases

55Some Some Household Household Acids and BasesAcids and Bases

Some Some Household Household Acids and BasesAcids and Bases

66Acids

Have a sour taste. Vinegar is a solution of acetic acid. CitrusHave a sour taste. Vinegar is a solution of acetic acid. Citrusfruits contain citric acid.fruits contain citric acid.

Will react with certain metals to produce hydrogen gasWill react with certain metals to produce hydrogen gas..

Will react with carbonates and bicarbonates to produce carbon Will react with carbonates and bicarbonates to produce carbon dioxide gas.dioxide gas.

Have a bitter taste.Have a bitter taste.

Feel slippery. Many soaps contain bases.Feel slippery. Many soaps contain bases.

Bases

77

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)

88

Some Properties of Bases

Produce OHProduce OH-- ions in water ions in water

Taste bitter, chalkyTaste bitter, chalky

Are electrolytesAre electrolytes

Feel soapy, slipperyFeel soapy, slippery

React with acids to form salts and waterReact with acids to form salts and water

pH greater than 7pH greater than 7

Turns red litmus paper to blue “Turns red litmus paper to blue “BBasasee = = BBluluee””

99

Some Common Bases

NaOHNaOH sodium hydroxidesodium hydroxide lyelye

KOHKOH potassium hydroxidepotassium hydroxide liquid soapliquid soap

Ba(OH)Ba(OH)22 barium hydroxidebarium hydroxide stabilizer for plasticsstabilizer for plastics

Mg(OH)Mg(OH)22 magnesium hydroxidemagnesium hydroxide “MOM” Milk of magnesia“MOM” Milk of magnesia

Al(OH)Al(OH)33 aluminum hydroxidealuminum hydroxide Maalox (antacid)Maalox (antacid)

1010

Reactions of acids and bases

HNO3 + KOH -> 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.

1111

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.

1212

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?

1313

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”.

1414Strong 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

SomeGROUP 2 hydroxides

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

1515

Weak Acids and Bases

• Some acids and bases ionize only slightly in water.

• These are considered weak.

• The most important weak base is ammonia.

1616

Balance of ions in acidic solutions

Acidic Neutral

Solution Solution

1717

ANIMATION LINKS

• Acid ionization equilibrium demo

1818

The The pH scalepH scale is a way of is a way of expressing the strength expressing the strength of acids and bases of acids and bases instead of using very instead of using very small numbers. small numbers. It ranges from 0-14.It ranges from 0-14.

Under 7 = acidUnder 7 = acid 7 = neutral 7 = neutral

Over 7 = baseOver 7 = base

1919

pH of Common pH of Common SubstancesSubstances

2020pH testing

• There are several ways to test pHThere are several ways to test pH

–Blue litmus paper (red = acid)Blue litmus paper (red = acid)

–Red litmus paper (blue = base)Red litmus paper (blue = base)

–pH paper (multi-colored)pH paper (multi-colored)

–pH meter (7 is neutral, <7 acid, >7 pH meter (7 is neutral, <7 acid, >7 base)base)

–Universal indicator (multi-colored)Universal indicator (multi-colored)

– Indicators like phenolphthaleinIndicators like phenolphthalein

–Natural indicators like red cabbage, Natural indicators like red cabbage, radishesradishes

2121

Indicators

2222Paper testing

• Paper tests like litmus paper and pH Paper tests like litmus paper and pH paperpaper

– Put a stirring rod into the solution Put a stirring rod into the solution and stir.and stir.

– Take the stirring rod out, and Take the stirring rod out, and place a drop of the solution from place a drop of the solution from the end of the stirring rod onto a the end of the stirring rod onto a piece of the paperpiece of the paper

– Read and record the color change. Read and record the color change. Note what the color indicates. Note what the color indicates.

– You should only use a small You should only use a small portion of the paper. You can use portion of the paper. You can use one piece of paper for several one piece of paper for several tests.tests.

2323pH 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.

2424

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?

2525WHAT 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

2626

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.

2727

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)

2828

How Does Acid Rain Form?

2929Formation 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.

3030

Formation of Acid Rain

3131

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

3232

3333Effects 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

3434Effects 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.

3535

3636Effects of Acid Rain

3737What 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)

3838

CAPT Activity: Brownfields• Link to North Haven Pharmacia and Upjohn

LLC site:

• http://www.upjohnnorthhaven.com/background.php