This document discusses acids and bases. It begins by defining the objectives of understanding acid and base definitions and theories. It then provides examples of common household and laboratory acids and bases. Next, it explains the Arrhenius theory that acids dissociate in water to form H+ ions and bases dissociate to form OH- ions. It also discusses the Brønsted-Lowry theory that acids donate protons and bases accept protons. Neutralization reactions between acids and bases to form salts and water are then explained. The document concludes by discussing acid-base conjugate pairs and examples.

2. OBJECTIVE:
1. To Understand the Definations of Acid and Base
2. To learn theories of acid and base
CONTENTS:
1. Examples of common acid base household and lab.
2. Arrhenius Theory
3. Neutralization

3. Common household
acids
Ethanoic acid
Lactic acid
Stearic acid
Acetylsailicylic
Acid

4.  Hydrochloric acid
 Nitric acid
 Sulfuric acid
 Phosphoric acid
- HCl
- HNO3
- H2SO4
- H3PO4

5.  Arrhenius was a Sweedish
chemist
 Put forward a theory of
acids in the 1880’s
 Stated that:
An acid is a substance that dissociates
in water to form H+ ions.

6. For example: when HCl is added to
water:
H+HCl + Cl-
In general:
HA H+ + A-

7.  HCl and HNO3 are monobasic acids as they donate
H+
one H+ ion.
HNO3 + NO3
-
 H2SO4 is a dibasic acid as it donates two H+ ions.
H2SO4 2H+ + SO4
2-
 H3PO4 is a tribasic acid as it donates three H+ ions.
H3PO4 3H+ + PO4
3-

8.  A strong acid is one which dissociates fully
in water
Example: HCl, H2SO4, HNO3
HCl + H2O H3O+ + Cl-
 A weak acid is one which does not fully
dissociate in water
Example: CH3COOH (ethanoic acid)
CH3COOH + H2O H3O+ + CH3COO-

9. Magnesium
hydroxide
Sodium hydrogen carbonate
Common household
bases
Sodium
hydroxide
Calcium hydroxide

10.  Sodium hydroxide
 Calcium hydroxide
 Ammonia
 Sodium carbonate
- NaOH
- Ca(OH)2
- NH3
- Na2CO3

11.  Arrhenius defined a base as:
A substance that dissociates in water to
produce OH- ions.
 For example: when NaOH is added to water:
NaOH Na+ + OH-
 In general:
XOH X+ + OH-

12.  A strong base is one which dissociates
fully in water
Example: NaOH
 A weak base is one which does not
fully dissociate in water
Example: Mg(OH)2

13.  Combining:
HA
XOH
H+
X+
+ A-
+ OH-
we get:
HA + XOH
acid + base
AX + H2O
salt + water

14. 1. The acids and bases must be in aqueous
solutions (i.e. water). This prevents the use of
other solvents benzene.
2. Not all acid – base reactions are in solution, e.g.
ammonia gas and hydrogen chloride gas produce
ammonium chloride.
3. According to Arrhenius, the salt produced should
not be acidic or basic. This is not always the
case, for example in the above reaction
ammonium chloride is slightly acidic

15.  Arrhenius thought that an acid gives off H+ ions in
solution.
 H+ ions are protons and can not exist
independently.
 When the acid dissociates, the H+ ions react with
water molecules:
H+ + H2O H3O+
 The H3O+ ion is called the hydronium ion.
 This is another limitation of the Arrhenius
theory.

16.  In 1923, Johannes Brønsted (a Danish
chemist) and Thomas Lowry (an English
chemist) proposed new definitions of acids
and bases.
Brønsted Lowry

17.  Brønsted and Lowry had worked
independently of each other but they both
arrived at the same definitions:
An acid is a substance that donates protons
(hydrogen ions).
A base is a substance that accepts protons.

18. + Cl-
 The HCl donates a proton and so is an acid
 The H2O, in this case, accepts a proton and so is a
base
Remember: Proton = H+
Donates a Proton
HCl + H2O H3O+
Accepts a Proton

19.  HNO3 + H2O
H3O+ + NO3-
and
 H2SO4
 HSO4-
+ H2O
+ H2O
H3O+ + HSO4-
H3O+ + SO4-2

20. NH3 + H2O
 The NH3 accepts a proton and so is a base.
 The H2O, in this case, donates a proton and
so is an acid.
Accepts a proton
NH4 + OH+ -
Donates a proton

21.  As can be seen from the previous two
examples, water is capable of acting
as both and acid and a base.
 Any substance that can act as both an
acid and a base is said to be
amphoteric.

22. Cl- + NH4+
Acid – Donates Protons
HCl + NH3
Base – Accepts Protons

23. The reaction between an acid and
a base to produce a salt and water
A salt is formed when the
hydrogen of an acid is replaced
by a metal (or ammonium ion)

24. Acid + Base Salt + Water
HCl + NaOH NaCl + H2O
but since the acid and base dissociate in water
we can write:
H+ + Cl- + Na+ + OH- Na+ + Cl- + H2O
we can cancel the Na+ and Cl- on bothsides
leaving:
H+ + OH- H2O

25. Indigestion remedies are
bases that neutralise excess
stomach acid
Lime is a base that
neutralises acid in soil
Toothpaste is a base
that neutralises acid in
the mouth

26. Wasp stings are basic
They can be neutralised
with vinegar or lemon
juice
Nettle, bee and ant stings
are acidic
They can be neutralised
with baking soda

27.  Acids and bases exist in pairs called
conjugate acid-base pairs.
 Every time an acid donates/loses a
proton, it becomes its conjugate base.
CH3COO- + H3O+
Example:
CH3COOH + H2O
Acid Conjugate Base

28. Likewise:
 When a base accepts a proton, it
becomes its conjugate acid.
4NH + + OH-
Example:
NH3 + H2O
Base Conjugate
Acid

29. H2SO4 HSO4
-
NH4
+
Acid
Conjugate
Base
+ H2O
Base
+ H3O+
Conjugate
Acid
Acid
NH3 + H2S
Base
Conjugate
Base
+ HS-
Conjugate
Acid