Acids, Bases, and Salts

Electrolytes

• An electrolyte is a substance that dissociates when dissolved in water. (Nonelectrolytes do not dissociate.)

• These compounds conduct electricity based on this dissociation.

• To dissociate means to separate into ions in solution.

• Acids, bases, and salts (ionic compounds) are all electrolytes.

Strong vs. Weak Electrolytes

• Strong electrolytes fully dissociate in water. (ex. Ionic compounds, strong acids, strong bases)

• Weak electrolytes only partly dissociate in water. (ex. Weak acids and weak bases)

• Nonelectrolytes do not dissociate in water. (nonpolar covalent compounds)

Write an equation for the dissociation of magnesium nitrate

in water.

Write an equation for the dissociation of the weak acid, HF, in

water.

Acids and Bases

Acids, bases, and salts make up compounds known as electrolytes.

Arrhenius acids – substances that ionize in water to produce the hydrogen ion, H+.

Arrhenius bases – substances that ionize in water to produce the hydroxide ion, OH-.

HCl(g) → H+(aq) + Cl-(aq)

NaOH(cr) → Na+(aq) + OH-(aq)

Dissociation – already formed ions separate

Ionization – neutral molecules react with water to form charged ions

Strength of Acids and Bases

Strength of acids and bases depends on how completely they ionize in water- the strongest acids and bases fully ionize in water while weak acids and bases only ionize slightly

Strong acids (Know these)– HCl, HBr, HI are all strong, while all other binary acids are weakAs a rule, all acids with at least two more oxygens than hydrogens are strong (H2SO4, HNO3,HClO4)

Strong bases – Hydroxides of the Groups I and II elements except for Be are all strong.

Acid Nomenclature

• In general, names of acids will begin with hydrogen.

• If the anion does not contain oxygen, the acid begins with hydro and ends in –ic

• HCl = hydrochloric acid• HBr = • HCN =

Acids containing oxygen

• If the acid contains oxygen, the acid does not have hydro at the start and either ends in ic or ous.

• If the anion ends in –ate use –ic• HNO3 = nitric acid• If the anion ends in –ite use –ous• H2SO3 = sulfurous acid

What is the formula for hydroiodic acid?

HI

HI2

H2I

HIO

3

0% 0%0%0%

1. HI2. HI2

3. H2I

4. HIO3

What is the formula for hydrocyanic acid?

H3N

HN

HCN

HSC

N

0% 0%0%0%

1. H3N

2. HN3. HCN4. HSCN

What is the formula for phosphoric acid?

H3PO3

H3PO4

HPO4

HPO3

0% 0%0%0%

1. H3PO3

2. H3PO4

3. HPO4

4. HPO3

What is the formula for sulfurous acid?

H2SO

3

H2SO

4 H

2S H

S2

0% 0%0%0%

1. H2SO3

2. H2SO4

3. H2S

4. HS2

What is the name of HNO2?

Hyd

ronitr

ic ac..

.

Hyd

ronitr

ous a...

Nitr

ous acid

Nitr

ic acid

0% 0%0%0%

1. Hydronitric acid2. Hydronitrous acid3. Nitrous acid4. Nitric acid

What is the name of HCl?

Hyd

roch

loric a...

Hyd

roch

lorous .

..

Chlorous a

cid

Chloric acid

0% 0%0%0%

1. Hydrochloric acid2. Hydrochlorous acid3. Chlorous acid4. Chloric acid

What is the name of HClO4?

Hyd

roch

loric a...

Chlorous a

cid

Chloric acid

Perchloric

aci...

0% 0%0%0%

1. Hydrochloric acid2. Chlorous acid3. Chloric acid4. Perchloric acid

Relative Strength of Acids and Bases

Conjugate Acids and Bases

• The strength of conjugate acids and bases are inversely proportional.

Kw

• Kw for water is based on the equation:

• 2H2O (l) -> OH- (aq) + H3O+ (aq)

• Kw = [OH-][H3O+] = 10-14

• Therefore, if you know either hydroxide or hydronium concentrations, you can solve for the other.

pH scale

pH is the measure of the concentration of hydronium ion in a water solution

pH = -log[H30+]

Scale goes from 0 to 14.0 to 7 is acidic, 7 is neutral, 7 to 14 is basic

pH – log based

• Every increase of 1 on the pH scale changes the concentration by a power of 10.

• How much stronger is a substance with a pH of 4 vs a pH of 6?

pOH scale

pOH is the measure of the concentration of hydroxide ion in a water solution

pOH = -log[0H-]

Also, pH + pOH =14

Neutralization Reaction

A neutralization reaction occurs when and acid and a base react to form water and a salt.

Acid + Base -> Water + Salt

***When the base has a CO32- ion, CO2 is also

produced.

Titrations

• Titrations are a quantitative lab technique that helps identify an unknown concentration of acid or base by titrating it against a titrant, or known acid or base concentration.

Titration Method

• Add an accurately measured volume of unknown acid (or base) to an Erlenmeyer flask

• Put 2-3 drops of phenolphthalein indicator to the unknown solution.

• Start adding the titrant and continue until the solution turns pink and stays pink.

Titration Tips

• Record the unknown’s volume by subtracting the ending vs. starting amount from buret (use the right amount of sig figs).

• You can add the titrant quickly at first but once it starts turning pink, swirl the flask and start adding more slowly. Swirl after each drop towards the equivalence point.