Acids and Bases

Our Goals for today To determine the difference between Acids & Bases and their properties. Explain how an acid can be neutralized by a base. Discuss pH and what it is.

General properties ACIDS Taste sour Turn litmus React with active metals – Fe, Zn React with bases BASES Taste bitter Turn litmus Feel soapy or slippery (react with fats to make soap) React with acids blue to red red to blue

Svante August Arrhenius (February 19, 1859 – October 2, 1927) Swedish chemist; Nobel Prize in Chemistry, 1903 * Arrhenius equation (activation energy) * Greenhouse effect Johannes Nicolaus Brønsted (February 22, 1879-December 17, 1947) Danish physical chemist Thomas Martin Lowry (October 26, 1874–November 2, 1936) English organic chemist Gilbert Newton Lewis (October 23, 1875-March 23, 1946) American physical chemist

Definitions Acids – produce H+ Bases - produce OH- Acids – donate H+ Bases – accept H+ Acids – accept e- pair Bases – donate e- pair Arrehenius only in water Bronsted-Lowry any solvent Lewis used in organic chemistry, wider range of substances

Acid Nomenclature Review No Oxygen w/Oxygen An easy way to remember which goes with which… “In the cafeteria, you ATE something ICky”

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 “Blue to Red A-CID”

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 “Basic Blue”

How do you neutralize an acid? How do you neutralize a base?

Neutralization HCl + NaOH  NaCl + HOH HCl + Mg(OH)2  In general: Acid + Base  Salt + Water All neutralization reactions are double displacement reactions. HCl + NaOH  NaCl + HOH HCl + Mg(OH)2 

How do we measure how acidic or basic something is?

The pH scale is a way of expressing the strength of acids and bases The pH scale is a way of expressing the strength of acids and bases. Instead of using very small numbers, we just use the NEGATIVE power of 10 on the Molarity of the H+ (or OH-) ion. Under 7 = acid 7 = neutral Over 7 = 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.

across United States in 2001 pH of Rainwater across United States in 2001 You are here! air masses Increasing acidity Why is the eastern US more acidic?

Indicators? How can we tell whether or not a substance is an acid or a base? Turn to page 238. What is an indicator?

Indicators Litmus Paper – litmus is a mixture of a different dyes that come from lichens. They are then absorbed into paper to be used as indicators. Phenolphthalein – colorless in acid and pink in a base.

Red Cabbage A natural indicator that changes a variety of different colors based on pH.

Red Cabbage Experiment Time