What is an acid? What is a base?

What are some properties of acids? Bases?

• Acids are solutions with many hydrogen ions.

• A common way of representing acids is H+

• Acids are solutions with many hydrogen ions.

• A common way of representing acids is H+

• In reality, the hydrogen ions combine with the water in the

acid to form hydronium (H3O+). Both have 1+ charge.

Properties of Acids

1) Produce H+ (as H3O+) ions in water

2) Taste sour

3) Corrodes metals

4) Behaves as a good electrolyte

5) Reacts with bases to form a salt and water

6) pH is less than 7

7) Turns phenolphthalein clear

8) Turns blue litmus paper to red

• “Blue to Red A-CID”

Uses of Acids

• H2SO4 is sulfuric acid.

• Most widely made industrial chemical in the world.

• Used to make paper, paint, detergent and fertilizers.

• Hypochlorous acid (HClO) is used in swimming pools to kill

algae

• HCl is in your stomach to help digest food

• Citric acid and ascorbic acid are in orange juice

• Carbonic acid and phosphoric acid are in soda

• Lots of hydroxide ions (OH-) makes something a base.

• It has a -1 charge.

Properties of Bases

1) Generally produce OH- ions in water

2) Taste bitter, chalky

3) Don’t react often with metals

4) Good electrical conductor

5) Feel soapy, slippery

6) React with acids to form salts and water

7) pH greater than 7

8) Turns phenolphthalein pink

9) Turns red litmus paper to blue “Basic Blue”

Uses of Bases

• NaOH (sodium hydroxide) is used to make soap and

paper, oven cleaners and products to unclog drains

• Ca(OH)2 (calcium hydroxide) is used to make cement and

plaster

• Ammonia (NH3) is found in household cleaners and used

to make fertilizer

• Magnesium hydroxide Mg(OH)2 is used in antacids to

treat heartburn.

How can we measure if something is acidic,

neutral, or basic?

• The pH values of several

common substances are

shown at the right.

• Many common foods are

weak acids

• Some medicines and many

household cleaners are

bases.

Indicators

• But what does an indicator actually measure?

• Indicators measure the proportion of H3O+:OH-

• http://phet.colorado.edu/sims/html/ph-scale/latest/ph-

scale_en.html

• Click MICRO & activate

• Hint: Water is Neutral

• pH is a measure of the H+ concentration of a solution.

high concentration of H+ = low pH

low concentrations of H+ = high pH

[OH-] = [H+]

[OH-] < [H+]

[OH-] > [H+]

Note!

pH is a logarithmic scale!

• Each whole number increase in magnitude represents a

10-fold increase in acidity or basicity.

pH 4 is 10x more acidic than pH 5.

pH 3 is 100x more acidic than pH 5.

pH 3 is 10x more basic than pH 2

pH 8 is 10,000x more basic than pH 4

ACID OR A BASE?

NaOH

HCl

Cu(OH)2

NH3

H2SO4

HCN

ACTIVITYReactivity of Acids & Bases

• Record your observations. Challenge yourself to figure

out what is made.

• EXPERIMENT 1: Put a piece of magnesium into a test

tube ¼ filled with hydrochloric acid.

• EXPERIMENT 2: Put a piece of magnesium into a test

tube ¼ filled with sodium hydroxide.

•

• EXPERIMENT 3: Put a piece of calcium carbonate into a

test tube ¼ filled with hydrochloric acid.

• EXPERIMENT 4: Put a piece of calcium carbonate into a

test tube ¼ filled with sodium hydroxide.

Coke Cans v.s. Acids & Bases

Ocean Acidification

LABProperties of Acids & Bases