1

Acids and Bases

2

Acids• React with certain metals to produce

hydrogen gas.• React with bicarbonates to produce

carbon dioxide gas

• Have a bitter taste• Feel slippery. • Many soaps contain bases.

Bases

3

Properties of Acids Produce H+ ions in water Taste sour

Corrode metals

Good Electrolytes

Ions used to transmit signals throughout the body

React with bases to form a salt and waterwater

pH is less than 7

Turns blue litmus paper to red “Blue to Red A-CID”

Some Common Acids

HCHC22HH33OO22 acetic acidacetic acid in vinegarin vinegar

HClHCl hydrochloric acidhydrochloric acid stomach acidstomach acid

HH33CC66HH55OO77 citric acidcitric acid fruitsfruits

HH22COCO22 carbonic acidcarbonic acid soft drinkssoft drinks

H3H322POPO44phosphoric acidphosphoric acid soft drinkssoft drinks

5

Properties of Bases Generally produce OHGenerally produce OH-- ions in water ions in water

Taste bitter, chalkyTaste bitter, chalky

Are electrolytesAre electrolytes

Feel soapy, slipperyFeel soapy, slippery

React with acids to form salts and React with acids to form salts and waterwater

pH greater than 7pH greater than 7

Turns red litmus paper to blueTurns red litmus paper to blue “ “BBasicasic BBluelue””

Some Common Bases

NaOHNaOH sodium hydroxidesodium hydroxide lyelye

KOHKOH potassium hydroxidepotassium hydroxide liquid soapliquid soap

Ba(OH)Ba(OH)22 barium hydroxidebarium hydroxide stabilizer for plasticsstabilizer for plastics

Mg(OH)Mg(OH)22 magnesium hydroxidemagnesium hydroxide “MOM” Milk of magnesia“MOM” Milk of magnesia

Al(OH)Al(OH)33 aluminum hydroxidealuminum hydroxide Maalox (antacid)Maalox (antacid)

The pH scale is a way of expressing the strength of acids and bases. Less than 7 = acid

7 = neutralGreater than 7 = base

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.

pH testing There are several ways to test pH

Blue litmus paper (red = acid)Red litmus paper (blue = basic)pH paper (multi-colored)

• **what we’ll usepH meter (7 is neutral, <7 acid, >7 base)Universal indicator (multi-colored)Indicators like phenolphthaleinNatural indicators like red cabbage,

radishes

pH indicators Indicators are dyes that can be

added that will change color in the presence of an acid or base.

Some indicators only work in a specific range of pH

Once the drops are added, the sample is ruined

Some dyes are natural, like radish skin or red cabbage