Module 4: Acids and Bases

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1

Simple way to identify compounds as acids or bases

Acids are compounds that being with H and bases are compounds that contain OH- (hydroxide).
-Example HF, HCl, KOH, NaOH

2

There are many definitions of how to classify substances as an acid or base. One of the most simplest definitions is

Arrhenius.

3

The problem with Arrhenius definition is it limits what compounds are acids and bases. which definition includes more substances and will be discussed later.

Bronsted-Lowry's definition

4

Arrhenius definition of Acids

produces hydrogen ions , H+, in solution.

5

Acid or base example?

HCl —> H+ Cl-

6

Acid or base example?

NaOH —> Na+ + OH—

7

Arrhenius definition of Bases

produce hydroxide ions, OH- in solution:

8

Strong acids and strong bases ionize

100% into ions in aqueous solutions.

9

Example of strong acid and bases or weak acid and bases?

Nitric acid is a strong acid and when it is in an aqueous solution, all of it exists as H+ and NO3 -1 ions.
-HNO3 (aq) → H+ (aq) + NO3 -1 (aq)
-100% as ions

10

Example of strong acid and bases or weak acid and bases?

Acetic acid: most of the acid exists as the acid and not as the ions.
HC2H3O2 (aq) ——-> H+ (aq) + C2H3O2-1 (aq)
-99.9 % exists as the molecule of acid
-0.1 % exists as the ions

11

Diprotic acids -

these types of acids give up 2 H+:
H2SO4 → 2H+ + SO4-2

12

Triprotic acids -

gives up 3 H+:
H3PO4 → 3H+ + PO4 -3

13

Hydrohalic acids:

a hydrogen ion that is attached to a halogen (X = F, Cl, I, Br)
-HF, HCl, HI, HBr. All of these are strong acids except HF is a weak acid.

14

Water as An Acid and A Base = What kind of Properties

Amphoteric

15

Water has unique properties and one such property is that water undergoes

autoionization. his means it self-ionizes.

16

Water produces both a hydrogen ion and a hydroxide ion making

it amphoteric

17

Amphoteric means it has properties of

both an acid and a base.

18

What equation shows water's amphoteric process

H2O + H2O→ H3O+ +OH-

19

Hydrogen Ion: H+ =

Hydronium Ion: H30+

20

The truth is that the hydrogen ion(H+) is actually

H3O+ and is called a hydronium ion

21

It actually is the correct way to express the hydrogen ion produced when an acid ionizes is Hydronium ion. However, most of the time because of laziness we express it in biology as

H+

22

Formation of H3O+ from the autoionization of water

The attraction of neighboring water molecule is attracted to a hydrogen from another water molecule by pulling it off.
-One of the water molecules has an extra hydrogen (H3O+) and the other water molecule now only has OH-1.
H2O + H2O → H3O+ + OH-