ACIDS AND BASES

· Define acids and bases in terms of the three definitions:· Arrhenius· Bronsted and Lowry· Lewis

· Define Amphoteric

· Identify and label conjugate pairs.

· Taste sour · Burn when touching skin. · Turn blue litmus red. · Neutralize basic solutions. · Corrosive to metals· strong or weak electrolytes

ACIDS

BASES· Taste bitter · Feel slippery· Turn red litmus blue · Neutralize acidic solutions· strong or weak electrolytes

Arrhenius Definition

yes, this is really him...looks happy, eh?

Svante Arrhenius (1859 - 1927)

Acids – Compounds that yield hydrogen ions (H+) in aqueous solution.

Bases – Compounds that yield OH- ions in aqueous solution.

HCl (aq) → H+ (aq) + Cl–

(aq)

NaOH (aq) → Na+ (aq) + OH–

(aq)

The Bronsted-Lowry Theory

20 years later:

An acid is a proton (H+) donor.

A base is a proton (H+) acceptor.

Lowry

Bronsted

NH3base~ no OH– ?

Ammonia accepts a proton from water:

NH3 (g) + H2O(l) NH4+

(aq) + OH-(aq)

H+

acceptor

Base is a proton (H+) acceptor:

Result is the H3O+ ion called the hydronium ion.H+ and H3O+ are written interchangeably.

HCl (g) + H2O(l) H3O+(aq) + Cl-

(aq)

H+

acceptordonor

NH3 (g) + HCl(g) NH4+

(g) + Cl-(g)

H+

Acids is a proton (H+) donor:

A substance which can act as either an acid or a base is described as being amphoteric.

Water is amphoteric.Bicarbonate ion is also amphoteric.

HCO3- + OH- CO3

2- + H2OH+

acceptordonor

HCO3-

+ H2O H2CO3 + OH-

H+

acceptor donor

Acids and bases accept and donate electrons, NOT protons.

Lewis acids accept (keep) electrons. Lewis bases donate (lose) electrons.

Gilbert Lewis Definition

CH3COO-(aq) + H2O(l) OH-

(aq) + CH3COOH (aq)

H+

base acid

Transition metal ions with charges of 2+ or 3+, create an acidic solution with water.

Step 1: Formation of a hydrate.

Step 2: Loss of H+ making acidic solution.

Fe(H2O)63+ + H2O H3O

+ + Fe(H2O)5(OH)2+ H+

H

Conjugate acid is what remains after a base has accepted a proton.

Conjugate base is what remains after the acid has donated its proton.

NH3 (g) + H2O(l)

base acid

NH4+

(aq) + OH-(aq)

Con. baseCon. acid

B + H2Obase acid

BH+ + OH-

Con. baseCon. acid

Each is called a conjugate pair.

HA + H2Obaseacid

H3O+ + A-

Con. baseCon. acid

· Arrhenius defined acids as substances which release H+ ions in water and bases as substances which release OH¯ ions in water.

· Bronsted and Lowry defined acids as proton donors and bases as proton acceptors.

· Substances that behave as BOTH acids and bases, these are called amphoteric.

· An acid and its conjugate base or a base and its conjugate acid are known as conjugate pairs.

CAN YOU / HAVE YOU? · Define acids and bases in terms of the three

definitions:· Arrhenius· Bronsted and Lowry· Lewis

· Define Amphoteric

· Identify and label conjugate pairs.