ACIDS AND BASES

Additional KEY TermsHydroxide Hydronium

• Outline the historical development of acid base theories.

Include: Arrhenius, Bronsted-Lowry, Lewis • Write balanced acid/base chemical equations.

Include: conjugate pairs, amphoteric

· 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

You should already be aware of most of these properties…except the taste. Don’t eat stuff in the lab, please.

1. Arrhenius Definition

Svante Arrhenius (1859 - 1927)

Acids • Yield hydrogen ions (H+) in aqueous solution

Bases • Yield hydroxide ions (OH-) in aqueous solution

H+ is also called a “proton” because a Hydrogen atom without its electron is just a proton (it has no neutrons)

HCl (aq) → H+ (aq) + Cl–

(aq)

NaOH (aq) → Na+ (aq) + OH–

(aq)

2. The Bronsted-Lowry Theory

Lowry

Bronsted

20 years later:

What about ammonia (NH3) Bronsted? It acts as a base, but doesn’t have OH-.

I guess we need I new definition for acid and base, Lowry!

Acids• proton (H+) donor

Base • proton (H+) acceptor

Ammonia accepts a proton from water:

NH3 (g) + H2O(l) NH4+

(aq) + OH-(aq)

H+

acceptor

Base is a proton (H+) acceptor:

donor

Follow the Hydrogen ion – who donated it, who accepted it.

H3O+ ion called the hydronium ion

H+

acceptordonor

Acids is a proton (H+) donor:

Hydrochloric acid donates a proton to water:

HCl(g) + H2O(l)

H+ H2O

H3O+(aq)

H3O+ splits apart quickly, so H3O+ and H+ are written interchangeably.

+ Cl-(aq)

Amphoteric: a substance which can act as either an acid or a base.

Water is amphoteric.Bicarbonate ion is also amphoteric.

HCO3- + OH- CO3

2- + H2OH+

acceptordonor

HCO3-

+ H2O H2CO3 + OH-

H+

acceptor donor

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

Step 1: Formation of a hydrate.

Water’s electrons are attracted to the BIG positive charge on Fe

Step 2: Loss of H+ making acidic solution.

Fe(H2O)63+ + H2O H3O

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

H

All electrons are attracted inwards, so Hydrogen ion has

nothing to lose and leaves

Acids Base • electron acceptor ● electron donor

3. Gilbert Lewis Definition

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

(aq) + CH3COOH (aq)

H+

base acidWhat about those metals? I think we need a broader

definition?

Negative ions have extra electrons to donate to the lonely

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

You are looking at the forward and reverse reactions – which compound donates for which direction?

B + H2Obase acid

BH+ + OH-

Con. baseCon. acid

Each is called a conjugate pair.

HA + H2Obaseacid

H3O+ + A-

Con. baseCon. acid

These are generic equations for an acid or base reaction

Additional KEY TermsHydroxide Hydronium

CAN YOU / HAVE YOU?

• Outline the historical development of acid base theories.

Include: Arrhenius, Bronsted-Lowry, Lewis • Write balanced acid/base chemical equations.

Include: conjugate pairs, amphoteric