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 redred to blue

Johannes Nicolaus Br ø nsted ( February 22, December 17, 1947 ) February December Danish physical chemist Svante August Arrhenius ( February 19, 1859 – October 2, 1927 ) February October Swedish chemist; Nobel Prize in Chemistry, 1903 * Arrhenius equation (activation energy) * Greenhouse effect Thomas Martin Lowry ( October 26, 1874–November 2, 1936 ) October November English organic chemist Gilbert Newton Lewis ( October 23, March 23, 1946 ) October March 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 Bronsted-Lowry Lewis only in water any solvent 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 þ Produce H + (as H 3 O + ) ions in water (the hydronium ion is a hydrogen ion attached to a water molecule) þ Taste sour þ Corrode metals þ Electrolytes þ React with bases to form a salt and water þ pH is less than 7 þ 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 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. Instead of using very small numbers, we just use the NEGATIVE power of 10 on the Molarity (Amount of stuff in concentration) 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.

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

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