C.6 Acid Contamination

Acids and Bases

Acids• Most acids are molecular

compounds.• All acids start with a

hydrogen atom(s).• Characteristics of acids:• Sour taste (vinegar)• React with bases to form

salts and water.• Conduct electricity• Change color of acid-base

indicators.

Hydrosulfuric AcidH2S

Common Acids

• Sulfuric Acid: H2SO4

• Phosphoric Acid: H3PO4

• Nitric Acid: HNO3

• Hydrochloric Acid: HCl

• Acetic Acid: H4C2O2

Sulfuric Acid: H2SO4

• Sulfuric acid is the most widely produced acid. 47 million tons a year is produced in the U.S. alone. Used in industry, as fertilizer, paint, dyes, detergents and automobile batteries.

Phosphoric Acid: H3PO4

• Phosphoric Acid contains phosphorus, which is an essential element for plants and animals.

• Used for fertilizers, animal feed and flavoring agent in beverages.

• Important for the manufacture of ceramics and detergents.

Nitric Acid: HNO3

• Nitric acid is a volatile, unstable liquid rarely used in industry.

• It denatures proteins, has a suffocating odor and stains skin.

• Used to make rubber, plastics, dyes and explosives.

Hydrochloric Acid: HCl

• Hydrochloric Acid is found in the stomach to digest food.

• Used to “pickle” (remove impurities) from iron and steel.

• Also used as a cleaning agent, food processing and in the activation of oil wells.

Acetic Acid: H4C2O2 or CH3COOH

• Acetic acid is a clear, colorless, pungent smelling liquid.

• Used to make vinegar, synthesize chemicals and manufacture plastics.

• Also used to manufacture food supplements and as a fungicide.

Bases

• Characteristics of Bases:

• Taste bitter• Change color of acid-

base indicators.• Feel slippery• React with acids to

produce salts and water.

• Conduct electricity

• Calcium hydroxide: Ca(OH)2

• Magnesium hydroxide: Mg(OH)2

• Potassium hydroxide KOH

• Sodium hydroxide NaOH

Calcium hydroxide: Ca(OH)2

• Used in mortar, plaster and cement.

• Also used in paper pulping and de-hairing animal hides. Yuck.

Calcium hydroxide plant

Magnesium hydroxide: Mg(OH)2

• The active ingredient in milk of magnesia.

• It reacts with the excess HCl in your stomach when you have a tummy ache and neutralizes it to form Magnesium chloride and water.

• Mg(OH)2 + HCl MgCl2 + H2O

• Please balance this equation.

Potassium hydroxide KOH

• Used in the manufacture of some liquid soaps.

• Also used in dyes, chemicals and pesticides.

Sodium hydroxide NaOH

• Sodium hydroxide NaOH

• A major industrial chemical.

• Used in drain and oven cleaners and converts animal fats to soap. Yuck.

Sodium hydroxide pellets

pH Scale

• The pH scale indicates how many H+

• Ions are in a solution.• A pH of 7 indicates a

neutral solution.• A pH of 7 -14 is a

basic solution.• A pH less than 7 is an

acidic solution.

Ions with a 1+ charge

• Positive ions are called cations.

• Na+ = sodium ion• K+

• NH4 + = ammonium

ion• Ca2+ = calcium ion

Ions released into the solar system

Ions with a 2+ charge

• Mg2+= magnesium ion• Ca2+ = calcium ion• Ba2+ = barium ion• Zn2+ = zinc ion• Cd2+ = cadmium ion• Hg2+ = mercury ion• Cu2+ = copper (II) ion• Pb2+ = lead (II) ion• Fe2+ = iron (II) ion

Ions with a 3+ and 4+ Charge

• Al3+ = Aluminum ion

• Fe3+ = Iron (III) ion

• Pb4+ = Lead (IV) ion• Sn4+ = Tin (IV) ion

Ions with a negative 1 charge• F- = Fluoride ion• Cl- = Chloride ion• Br- = Bromide ion• I- = Iodide ion• NO3

- = Nitrate ion• OH- = Hydroxide ion• HCO3

- = Hydrogen carbonate (bicarbonate)

• NOTE** Any ions with more than one element are called polyatomic ions.

Ions with a negative 2 charge

• O2- = Oxide ion• S2- = Sulfide ion

• SO42- = Sulfate ion

• SO32- = Sulfite ion

• CO32- = Carbonate

ion

Ions with a negative 3 charge

• PO43- = Phosphate

ion

• PO33- = Phosphite

ion

• AsO43- = Arsenate

ion

Ionic compounds

• Finish the following equations and balance:

• K + O2 ______ (potassium oxide)

• Mg + Cl2 ____ (magnesium chloride)

• Na + Cl ____ (sodium chloride)

• Your Turn on page 57.

C.8 Dissolving Ionic Compounds• Ionic compounds

dissolve because of the attractive forces between the ionic crystal and the polar ends of water molecules. It’s like a tug of war where the positive ions are attracted to the negative part of the water and the negative ions are attracted to the positive part of the water.

C.9 Heavy Metal Ion Contamination• Heavy metals are generally heavier than many

metals that are essential to human health such as Ca2+ or K+.

• The most dangerous heavy metals are those of Pb2+, Hg2+ and Cd2+ which are toxic even in small amounts.

• These ions can attach to proteins and cause damage to the nervous system, kidneys, liver, probable mental retardation, and even death.

• These metals are not removed as waste as they travel through the food chain—they remain in the body.

Lead

• Pb—Plumbum• Lead can be present in many places. Once used for plumbing and a

gasoline additive.• Most of the lead ingested through water supplies is excreted in the urine.• The limit for lead in a child’s blood is 10 micrograms per deciliter before

medical intervention is recommended.• It’s estimated that 1 out of 6 children under age six in the U.S. has a blood

level over 10 micrograms per deciliter.

Mercury

• Hg—Hydragyrum• Mercury is the only metal that is a liquid at room temperature. • Mercury vapor is quite poisonous.• Organic compounds containing methylmercury ions (CH3Hg) can

get into the water supply and cause severe brain, nerve damage and death. It has also been linked to autism in children.

Cadmium• Cd• Used in photography

and in paint manufacturing.

• It is very toxic producing headaches, coughing and vomiting.

• It can accumulate in the liver and kidneys causing irreparable damage.

• You Decide pg. 62/63

•

C.11 Molecular Substances in the River

• When the attractive forces between the nuclei of two or more atoms is not strong enough to transfer electrons, the electrons are shared.

• Polar molecules will dissolve in “polar” water.

• Nonpolar molecules will NOT dissolve in water. An example is oil.

• Therefore, “like” dissolves “like”.• Part C: Summary Questions