Acids and Bases

What is an Acid?

Acid – a substance that produces H+ (hydrogen ions) in solution. It is the ability to produce the H+ ions that gives acids their characteristic properties.

Properties of Acids

• Acids taste sour. (never use taste to test for the presence of an acid. They can cause tissue damage.)

• Acids are electrolytes and can conduct electricity

Properties of Acids

• Acids are corrosive – they react strongly with metals and “eat away“ at the metals producing hydrogen gas. Contact with skin may result in severe burns and tissue damage

• Acids react with indicators, organic compounds that changes color in a n acid or a base.

Acids Affect Indicators, by changing their color

Blue litmus paper turns red in contact with an acid (and red paper stays

red).

Some Common AcidsName Formula Where Found

Acetic acid CH3COOH vinegar

Acetylsalicylic acid HOOC-C6H4-OOCCH3 aspirin

Ascorbic acid H2C6O6 citrus fruits

Boric acid H3BO3 eyewash solutions

Hydrochloric acid HCl gastric juice in stomach

Carbonic acid H2CO3 carbonated drinks

Sulfuric acid H2SO4 car batteries, fertilizers

How are acids used?• sulfuric acid – car batteries, fertilizer,

dehydrating agent (removes H2O from materials).

• Phosphoric Acid – fertilizers, used in soft drinks. Harmful to environment when added to detergents.

• Nitric acid – fertilizers, explosives.• Hydrochloric acid – used to clean surfaces in

industry. also known as muriatic acid.

What is a Base?

base – substance that produces hydroxide ions, OH-, in a solution.

Properties of Bases

• Most bases are crystalline solids.• In solution, bases feel slippery, like soap.• Bases taste bitter. • Bases are corrosive – contact with skin may result

in severe burns and tissue damageNEVER USE TASTE TO TEST FOR THE PRESENCE OF A

BASE. THEY CAN CAUSE TISSUE DAMAGE

Properties of Bases

• Bases are electrolytes and conduct electricity.• Bases react with indicators to produce a

predictable color change.

Common Bases and Their UsesName Formula Uses

Aluminum hydroxide Al(OH)3 deodorant, antacid

Calcium hydroxide Ca(OH)2 Leather production, manufacture of mortar and plaster

Magnesium hydroxide Mg(OH)2 laxative, antacid

sodium hydroxide NaOH drain cleaner, soap making

Ammonia NH3 household cleaner, fertilizer,production of rayon and nylon

Strength of Acids and Bases

• Strong acids – ionizes almost completely in solution (very soluble)

• Weak acids – acid that only partly ionizes in solution (slightly soluble)

• Strong base – dissociates completely in solution (very soluble)

• Weak base – base that only partly dissociates in solution (slightly soluble)

Strength and Concentration

• Concentration – the amount of acid or base dissolved in solution (g/100 mL)

• Strength – refers to the ease that the acid or base forms ions in solution. The more ions that are produced the stronger the acid or base

What is pH?pH is the measurement of

H3O+ (hydronium ions) in solution.

pH is a scale used to measure

how acidic or basic a solution is.

Below 7 is acidicAbove 7 is basic7 is neutral

Acids have a

pH less

than 7

Baseshave a

pH greater than 7

Acids have a

pH less

than 7

Baseshave a

pH greater than 7