Acids and Bases

Acid

Group of compounds with some common properties when in solution

1st – taste sour 2nd – change the color of certain

dyes called indicators 3rd – most react with active

metals to release hydrogen gas

4th – acids react with bases to produce neutral salt and water

5th – acids conduct electric current

Properties of Bases

Bases taste bitter Feel slippery to the skin Bases change color of indicators React with acid to form water and

a salt Are electrolytes Excellent cleaning agents

Arrhenius Definition

Acid ionize to form H+ (H3O+)

Base ionize to form OH-

Bronsted Acid and Base Bronsted Acid – proton (H+) donor Bronsted Base – proton acceptor

NH3 + H2O NH4+ + OH-

Bronsted definition is broader than Arrhenius – more things can be considered bases

For each reaction identify the acid and base

CH3NH2 + H2O CH3NH3 + OH-

HSO4- + H2O H3O+ + SO4

2-

Amphoteric

In the last example we saw that water could act as either an acid or a base depending on what it reacted with

Water is amphoteric – can act as either an acid or a base

The strength of an acid (or base) is determined by the amount of IONIZATION.

The strength of an acid (or base) is determined by the amount of IONIZATION.

Strong vs. Weak Acids

Strong acid is one that ionizes completely

HNO3 (aq) ---> H+ (aq) + NO3- (aq)

Weak acids are much less than 100% ionized in water.

One of the best known is acetic acid =

CH3CO2H

Weak AcidsWeak Acids

Base Strength

Any substance that ionizes completely to form OH- ions are strong bases

These solutions are said to be alkaline

All highly soluble hydroxides are strong bases

Acid/Base Reactions

Whenever an acid and base react, two conjugates are produced

Conjugate base – the species that remains after the acid has given up its proton

Conjugate acid – the species that remains after the base has accepted the proton