Acids and Bases

These are acids…..HNO3

HClH2SO4

HC2H2OOH

H3PO4

What do they all have in common?

What all acids have in common…Sour or tart taste (take my word for it)Electrolytes in solutionReact with metals to produce H2(g)

React with bases to produce water and a salt

Change the color of an acid/base indicator

Many are in foods and drinks.

These are all bases….

NaOHKOHCa(OH)2

Mg(OH)2

What do they all have in common?NH3 is also a base.

What all bases have in common… Taste bitter (take my word for it)

Feel slippery on skin (take my word for it) Electrolytes in solution Change the color of an acid/base indicator React with acids to produce water and a

salt Almost none are in foods.

Arrhenius Acids and BasesAcids ionize in water to produce

hydrogen ions (H+)HCl + H2O → H+

(aq) + Cl-(aq)

Bases ionize in water to produce hydroxide ions (OH-)

NaOH + H2O → Na+(aq) + OH-

(aq)

Brönsted-Lowry Acids and BasesAn acid donates a hydrogen ion (H+)HCl + H2O → H+

(aq) + Cl-(aq)

A base accepts a hydrogen ionNH3(g) + H2O(l) → NH4

+(aq) + OH-

(aq)

That’s why NH3 is listed as a base!

Conjugate Acids and Bases

HCl + H2O → H+(aq) + Cl-(aq)

A more accurate version is this:HCl + H2O ↔ H3O+ + Cl-

H3O+ is called hydronium ionWe are agreed that reactions

are reversible, right?

Self-Ionization of Water Sometimes water comes apart: H2O ↔ H+

(aq) + OH-(aq)

If [H+] = [OH-] you have a neutral solution In H2O, [H+] = 1.0 x 10-7M. So is [OH-]

For any aqueous solution,

[H+] x [OH-] = 1 x 10-14

This is called the ion-product constant for water, Kw = [H+] x [OH-] = 1.0 x 10-14

Self-Ionization of Water

In an acidic solution, [H+] > [OH-] In an acidic solution, [H+] > 1.0 x 10-7M In a basic solution, [OH-] > [H+] In a basic solution, [H+] < 1.0 x 10-7MpH = -log[H+]

pHpH = -log[H+] In a neutral solution, [H+] = 1.0 x 10-7MWhat is the pH? If [H+] = 4.8 x 10-8M, what is the pH? If pH = 3.32, what is [H+]? [H+] = antilog(-pH)

Titration Method of determining the concentration of an acid/base.

Let’s say you have an acid of unknown concentration.

You add a base, whose concentration is known, until an indicator shows that you are at the equivalence point.

Equivalence point is where moles of acid=moles of base.

Titration

At the equivalence point, MaVa=MbVb

During the actual titration, it is HUGELY important that you do not overrun the equivalence point.

Example: 40.0mL of a nitric acid solution required 32.6mL of 0.50M NaOH to neutralize it. What is the molarity of the nitric acid?

Strong/Weak Acids & Bases

Strong/Weak Acids & BasesWhat do acids do in water?They IONIZESome ionize completely (strong),

and some hardly ionize at all (weak).

Strong acids: HCl, H2SO4, HNO3,

H3PO4, H2CO3, HClO,CH3COOH

Strong/Weak Acids & BasesKa, the acid dissociation constant,

is a ratio that numerically expresses how strong an acid is.

Strong acids have a high Ka value (1 or higher), and weak acids have a low Ka value (far below 1).

Salt Hydrolysis RxnsWhen salts dissolve in water, they

dissociate into their component ions.

Some of these ions act as weak Bronsted-Lowry acids or bases.

There are four possibilities….

1. Salts of Strong Acids and Bases— (NaCl, K2SO4) produce neutral solutions

1. Salts of Strong Acids & Weak Bases– (NH4Cl) produce slightly acidic solutions

3. Salts of Weak Acids & Strong Bases—(Na2CO3)produce slightly basic solutions.

4. Salts of Weak Acids and Bases— can produce either acidic, basic, or neutral solutions. Very hard to predict

Strong Acids

H2SO4—Sulfuric

HNO3—NitricAll of the hydrogen halides except

fluorine (HCl—Hydrochloric, HBr—Hydrobromic, HI—Hydroiodic)

Strong Bases

All of the hydroxides of the alkali metals (LiOH, NaOH, KOH, RbOH, CsOH)

The hydroxides of the alkaline earth metals except for Be and Mg (Ca(OH)2, Sr(OH)2, Ba(OH)2)