Acids, Bases, and pH

Glencoe: Chapter 24 Sections 3 and 4Pages 764-774

I. What are acids?

Substances that donate hydrogen ions, Substances that donate hydrogen ions, HH++, to form hydronium ions, H, to form hydronium ions, H33OO++, when , when dissolved in water dissolved in water

Formation of Hydronium Ions

1+

hydronium ion

H3O+

+

hydrogen ion

H+

water

H2O

1+

(a proton)

1+

A. Characteristics of acids

1. Acids turn 1. Acids turn blueblue litmus paper litmus paper redred

Litmus paper is an indicatorLitmus paper is an indicator

2. Acids taste sour2. Acids taste sour

3. Can burn skin3. Can burn skin

Common Acids

Sulfuric AcidSulfuric Acid HH22SOSO44

Nitric AcidNitric Acid HNOHNO33

Phosphoric AcidPhosphoric Acid HH33POPO44

Hydrochloric AcidHydrochloric Acid HClHCl

Acetic AcidAcetic Acid CH CH33COOHCOOH

Carbonic AcidCarbonic Acid H H22COCO33

Battery acid

Used to make fertilizersand explosives

Food flavoring

Stomach acid

Vinegar

Carbonated water

B. Strong vs. Weak acids

1. Strong acids – ionize (break in to 1. Strong acids – ionize (break in to cations and anions) almost cations and anions) almost completely, and conduct completely, and conduct electricity well electricity well

a. Nitric acid (HNOa. Nitric acid (HNO33))

b. Hydrochloric acid (HCl) b. Hydrochloric acid (HCl)

c. Sulfuric acid (Hc. Sulfuric acid (H22SOSO44))

d. Perchloric acidd. Perchloric acid

B. Strong vs. Weak acids

2. Weak acids – do not completely 2. Weak acids – do not completely ionizeionize

a. Acetic acid (vinegar)a. Acetic acid (vinegar)

b. Citric acidb. Citric acid

c. ALL othersc. ALL others

II. What are bases?

- Substances that form hydroxide ions - Substances that form hydroxide ions (OH(OH--) ions when in water, or accept H) ions when in water, or accept H++ ionsions

A. Characteristics of Bases

1. Taste bitter1. Taste bitter

2. Slippery2. Slippery

3. Bases turn 3. Bases turn redred

litmus paper litmus paper blueblue

4. Can burn skin4. Can burn skin

B. Strong vs. Weak bases

1. Strong bases - ionize (break into 1. Strong bases - ionize (break into cations and anions) almost cations and anions) almost completely, and conduct electricity completely, and conduct electricity well well

a. KOH – potassium hydroxidea. KOH – potassium hydroxide

b. NaOH – sodium hydroxideb. NaOH – sodium hydroxide

2. Weak bases - do not completely 2. Weak bases - do not completely ionizeionize

a. Ammonia (NHa. Ammonia (NH33))

Review Acid:Acid: A solution that has an excess of H A solution that has an excess of H++

ions. It comes from the Latin word acidus ions. It comes from the Latin word acidus that means "sharp" or "sour". that means "sharp" or "sour".

Base:Base: A solution that has an excess of A solution that has an excess of OHOH-- ions. Another word for base is alkali. ions. Another word for base is alkali.

Aqueous:Aqueous: A solution that is mainly A solution that is mainly water. Think about the word aquarium. water. Think about the word aquarium. AQUA means water. AQUA means water.

III. Why is a substance neutral?

A substance is neutral when: A substance is neutral when:

1. It does not ionize at all, 1. It does not ionize at all, therefore notherefore no

HH++ or OH or OH-- ions ions

2. It has equal concentrations2. It has equal concentrations

(amounts) of H(amounts) of H++ and OH and OH-- ions ions

IV. How acidic or basic is it?

A. pH – measures the concentration of HA. pH – measures the concentration of H33OO++ ions ions

Crowded Crowded Not Crowded Not Crowded

More crowded = More concentratedMore crowded = More concentrated Critical to certain processes and functionsCritical to certain processes and functions

- example: enzymes, blood- example: enzymes, blood B. pH B. pH indicates H indicates H33OO++ and OH and OH- - concentrationsconcentrations

Concentration vs. Strength

Concentration is not the same as Concentration is not the same as strengthstrength

Concentration deals with the amount of Concentration deals with the amount of hydronium ions in the solution, compared hydronium ions in the solution, compared to the amount of water in the solution.to the amount of water in the solution.

More acid or base and less water More acid or base and less water

= more concentrated= more concentrated

More ions and less molecules More ions and less molecules

= stronger= stronger

III. How acidic or basic is it?

C. pH scale C. pH scale 0-14 0-14

Indicates concentration of hydronium Indicates concentration of hydronium ionsions

0-6 = acid 0-6 = acid closer to 0 is more acidic closer to 0 is more acidic

8-14 = base 8-14 = base closer to 14 is more basic closer to 14 is more basic

7 = neutral 7 = neutral H H33OO++ concentration = OH concentration = OH-- concentrationsconcentrations

III. How acidic or basic is it?

D. Each pH unit = a power of tenD. Each pH unit = a power of ten

- Example: pH 3 is 100 times more - Example: pH 3 is 100 times more acidic than pH 5acidic than pH 5

Review Strong Acid:Strong Acid: An acid that has a very low pH (0-4). An acid that has a very low pH (0-4).

Strong Base:Strong Base: A base that has a very high pH (10-14). A base that has a very high pH (10-14).

Weak Acid:Weak Acid: An acid that only partially ionizes in an An acid that only partially ionizes in an aqueous solution. That means not every molecule aqueous solution. That means not every molecule breaks apart. They usually have a pH close to 7 (3-6). breaks apart. They usually have a pH close to 7 (3-6).

Weak Base:Weak Base: A base that only partially ionizes in an A base that only partially ionizes in an aqueous solution. That means not every molecule aqueous solution. That means not every molecule breaks apart. They usually have a pH close to 7 (8-10). breaks apart. They usually have a pH close to 7 (8-10).

Neutral:Neutral: A solution that has a pH of 7. It is neither A solution that has a pH of 7. It is neither acidic nor basic. acidic nor basic.