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

Johannes Nicolaus Brønsted (February 22, 1879-December 17, 1947)Danish physical chemist

Svante August Arrhenius (February 19, 1859 – October 2, 1927)

Swedish chemist; Nobel Prize in Chemistry, 1903

* Arrhenius equation (activation energy)

* Greenhouse effect

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

Bronsted-Lowry

Lewis

only in water

any solvent

used in organic chemistry,wider range of substances

Anion Ending Acid Name

-ide hydro-(stem)-ic acid

-ate (stem)-ic acid

-ite (stem)-ous acid

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 H3O+) 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 = acid7 = 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 Rainwateracross United States in 2001

Incre

asin

g a

cidity

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