Acids and Bases

Thursday, March 3

Acids Versus Bases

Acid Base (Alkali)Conductivity

Litmus Paper

Phenolphthalein

pH

Magnesium

(and other reactive metals)

Good conductor Good conductor

Blue litmus red Red litmus blue

Turns clear Turns pink

< 7 > 7

Reacts to form hydrogen gas + salt

No reaction

Acids Versus BasesAcid Base (Alkali)

Feel

Taste

Formula

Wet (no characteristic feel)

Slippery

Sour Bitter

Usually begins with hydrogen

• HCl –hydrochloric acid• H2SO4 – sulfuric acid• CH3COOH – acetic acid

Most bases contain the hydroxide ion (OH-)

• NaOH – sodium hydroxide• NH3 – ammonia•CO3

2- - carbonate•HCO3

1- - bicarbonate

Acids Versus Bases

Acid Base (Alkali)Def’n Acids are substances that

DONATE H+ ions in aqueous solution.

Eg.

HCl(aq) H+(aq) + Cl-(aq)

Bases are substances that give DONATE OH- ions in aqueous solution.

Eg.

NaOH(aq) Na+(aq)+ OH-

(aq)

The pH scale is logarithmic which means:

a pH of 1

is ten times more acidic than

a pH of 2.

The pH ScaleAcid Neutral Base

# of H+ ions

pH

Many Moderate Few

Low pH(from 1 to < 7 ) 7

High pH ( > 7)

The lower the pH, the stronger the

acid

The higher the pH, the stronger the

base

6. Neutralization What?

Acid and a base mix to form a salt and water

Acid + Base Salt + Waterproduces H+ ions

produces OH- ions

Lots of types

General Formula:

HxA + B(OH)y AB + H2O

Homework

Read pp. 293-295P. 295 (Q # 2, 3, 4)

Read pp. 296-299P. 299 (Q # 1 - 7)

Neutralization Examples:

hydrochloric acid + sodium hydroxide sodium chloride + water

HCl + NaOH NaCl + H2O

nitric acid (pg 198) + calcium hydroxide calcium nitrate + water

2HNO3 + Ca(OH)2 Ca(NO3)2 + 2H2O