Acids & Bases

Goals for today To determine the difference between Acids & Bases Discuss the importance of studying Acids & Bases

What is the pH scale? The pH scale measures how acidic or basic a solution is.

The pH scale Range of 0 - 14 Pure water has a pH of 7 and is considered a “neutral solution” (it is not an acid or a base)

Identifying Acids and Bases Acids have a ph from 0-7 Lower pH value indicates a stronger acid. Bases have a pH from 7-14 Higher pH value indicates a stronger base.

Did we Miss something?? What happens when the pH of a substance is 7? Ans: A pH level of 7 indicates a Neutral Substance i.e: Water!

Test Your Knowledge What is the range of an ACID on the pH scale? Ans: 0-7 What is the range of a BASE and what is another name for a BASE? Ans: 7-14, Alkaline

Characteristics Of Acids A sour taste. It turns blue litmus paper red It tastes sour. Try drinking lemon juice (citric acid) React with certain metals React with bases How do you know if a chemical is an acid? It usually starts with Hydrogen. HCl, H2SO4, HNO3, etc. (but not water!)

Acids React with Carbonates and Bicarbonates HCl + NaHCO3 Hydrochloric acid + sodium bicarbonate NaCl + H2O + CO2 salt + water + carbon dioxide An old-time home remedy for relieving an upset stomach

Effects of Acid Rain on Marble (marble is calcium carbonate) George Washington: BEFORE acid rain George Washington: AFTER acid rain

How acids are used in the real world!!!!

Sulfuric Acid = H2SO4 Highest volume production of any chemical in the U.S. (approximately 60 billion pounds/year) Used in the production of paper Used in production of fertilizers Used in petroleum refining; auto batteries

Nitric Acid = HNO3 Used in the production of fertilizers Used in the production of explosives Nitric acid is a volatile acid – its reactive components evaporate easily Stains proteins yellow (including skin!)

Hydrochloric Acid = HCl Used in the “pickling” of steel Used to purify magnesium from sea water Part of gastric juice, it aids in the digestion of proteins Sold commercially as Muriatic acid

Phosphoric Acid = H3PO4 A flavoring agent in sodas (adds “tart”) Used in the manufacture of detergents Used in the manufacture of fertilizers Not a common laboratory reagent

Acetic Acid = HC2H3O2 (also called Ethanoic Acid, CH3COOH) Used in the manufacture of plastics Used in making pharmaceuticals Acetic acid is the acid that is present in household vinegar

Characteristics of Bases A Base is characterized by: A bitter taste. (Milk of Magnesia) It feels slippery. (Soapy Water) It turns Red Litmus Blue. React with acids

How bases used in the real world!!!

Examples of Bases (metallic hydroxides) Sodium hydroxide, NaOH (lye for drain cleaner; soap) Potassium hydroxide, KOH (alkaline batteries) Magnesium hydroxide, Mg(OH)2 (Milk of Magnesia) Calcium hydroxide, Ca(OH)2 (lime; masonry)

Measuring acid or base? 1. Litmus paper – turns red in an acid, blue in base. 2. Phenolphthalein – Used to test for the presence of a base. It is clear and turns bright pink in a base and stays clear in acids. 3. pH paper – Uses a range of colors that indicates the pH.

Why Learn about Acids & Bases? What do you think is the pH level of tap water? The pH of a swimming pool must be checked periodically. Why? Is it important for Lakes & Rivers to maintain a certain pH?