Chapter 19“Acids, Bases,

and Salts”

Properties of Acids & Bases!

electrolytes

turn litmus redsour taste

react with metals to form H2 gas

slippery feel

turn litmus bluebitter taste

ChemASAP

vinegar, milk, soda, apples, citrus fruits

ammonia, lye, antacid, baking soda

electrolytes

don’t react w/metals

“clean” feel

pH < 7 pH > 7Produce OH– ions in H2O

Produce H+ ions in H2O

Properties

• Electrolytes can conduct electricity–Can be strong or weak electrolytes in

aqueous solution

Acids have a pH less than 7

Acids Affect Indicators

Blue litmus paper turns red in contact with an acid.

Acids React with Active Metals

Acids react with active metals to form salts and hydrogen gas:HCl(aq) + Mg(s) → MgCl2(aq) + H2(g)

How can you tell if the gas produced is hydrogen?

Acids React with Carbonates

2HC2H3O2 + Na2CO3

2NaC2H3O2 + H2O + CO2

Effects of Acid Rain on Marble(calcium carbonate)

George Washington:BEFORE

George Washington:AFTER

Bases have a

pH greater than 7

Bases Affect Indicators

Red litmus paper turns blue in contact with a base.

Phenolphthalein turns purple in a base.

Vid properties

Different Acid & Base Definitions

Definitions• ArrheniusArrhenius - In aqueous solution (when - In aqueous solution (when

dissolved in water)…dissolved in water)…

HCl + H2O H3O+ + Cl– •AcidsAcids form hydronium ions (H3O+) (or H+)

H

HH H H

H

ClClO O

–+

acidCourtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

Arrhenius said: An acid can be defined as a substance that

yields hydrogen ions (H+) when dissolved in water.

HCl•Pure, dry substance is hydrogen chloride•When dissolved in water it’s hydrochloric acid… it breaks into H+ ions & Cl- ions

2.7

A base can be defined as a substance that yields

hydroxide ions (OH-) when dissolved in water.

NaOH sodium hydroxideKOH potassium hydroxideBa(OH)2 barium hydroxide

Definitions

• ArrheniusArrhenius - In aqueous solution… - In aqueous solution…

•BasesBases form hydroxide ions (OH-)

NH3 + H2O NH4+ + OH-

H

H

HH H

H

N NO O–+

HH

H H

baseCourtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

Video 1

Definitions

• Brønsted-LowryBrønsted-Lowry

HCl + H2O Cl– + H3O+

•AcidsAcids are proton (H+) donors. •BasesBases are proton (H+) acceptors.

conjugate acidconjugate base

baseacid

Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

Acids and bases come in pairs• A “conjugate base” is the

remainder of the original acid, after it donates it’s proton/hydrogen ion

• A “conjugate acid” is the particle formed when the original base gains a proton/hydrogen ion

• Indicators are weak acids or bases that have a different color from their original acid and base

Definitions

H2O + HNO3 H3O+ + NO3–

CBCAAB

Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

H

H

OH O

O

ON

Base Acid

Acids and bases come in pairs• Amphoteric – a substance that can act as both

and acid and base- as water shows

Video 2

Definitions• Lewis –Lewis – same guy who came up with the

Lewis-dot structures

• AcidsAcids are electron pair acceptors. • BasesBases are electron pair donors.

Lewis base

Lewis acid

Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

Acid Definitions

Lewis acids

Bronsted-Lowry

Arrheniusacids

The Arrhenius model of acids and bases was broadened by the Bronsted-Lowry model.

The Bronsted-Lowry model was broadened by the Lewis model

The Lewis acid-base model is the most general in scope.

Ralph A. Burns, Fundamentals of Chemistry 1999, page 483

Acid – Base Systems

Type Acid Base

Arrhenius H+ or H3O + producer

OH - producer

Bronsted-

Lowry

Proton (H +) donor

Proton (H +) acceptor

Lewis Electron-pair acceptor

Electron-pair donor