1. ACID AND BASE
Submitted by : Macallan, Leewhere G.
Rizano, Gerald
III-Avogadro
Submitted to : Mrs. Mary Grace Bumanlag

2. AN ACID–BASE REACTION IS A CHEMICAL
REACTION THAT OCCURS BETWEEN
AN ACID AND A BASE. SEVERAL CONCEPTS
EXIST THAT PROVIDE ALTERNATIVE
DEFINITIONS FOR THE REACTION
MECHANISMS INVOLVED AND THEIR
APPLICATION IN SOLVING RELATED
PROBLEMS. DESPITE SEVERAL DIFFERENCES
IN DEFINITIONS, THEIR IMPORTANCE BECOMES
APPARENT AS DIFFERENT METHODS OF
ANALYSIS WHEN APPLIED TO ACID–BASE
REACTIONS FOR GASEOUS OR LIQUID
SPECIES, OR WHEN ACID OR BASE
CHARACTER MAY BE SOMEWHAT LESS
APPARENT. THE FIRST OF THESE SCIENTIFIC
CONCEPTS OF ACIDS AND BASES WAS
PROVIDED BY THE FRENCH CHEMIST ANTOINE
LAVOISIER, CIRCA 1776
Acid–base
reaction

3. THE FIRST SCIENTIFIC CONCEPT OF ACIDS AND BASES WAS PROVIDED
BY LAVOISIER CIRCA 1776. SINCE LAVOISIER'S KNOWLEDGE
OF STRONG ACIDS WAS MAINLY RESTRICTED TO OXOACIDS, SUCH
AS HNO
3 (NITRIC ACID) AND H
2SO
4 (SULPHURIC ACID), WHICH TEND TO CONTAIN CENTRAL ATOMS IN
HIGH OXIDATION STATES SURROUNDED BY OXYGEN, AND SINCE HE
WAS NOT AWARE OF THE TRUE COMPOSITION OF THEHYDROHALIC
ACIDS (HF, HCL, HBR, AND HI), HE DEFINED ACIDS IN TERMS OF
THEIR CONTAINING OXYGEN, WHICH IN FACT HE NAMED FROM GREEK
WORDS MEANING "ACID-FORMER" (FROM THE GREEK ΟΞΥΣ (OXYS)
MEANING "ACID" OR "SHARP" AND ΓΕΙΝΟΜΑΙ (GEINOMAI) MEANING
"ENGENDER"). THE LAVOISIER DEFINITION WAS HELD AS ABSOLUTE
TRUTH FOR OVER 30 YEARS, UNTIL THE 1810 ARTICLE AND
SUBSEQUENT LECTURES BY SIR HUMPHRY DAVY IN WHICH HE
PROVED THE LACK OF OXYGEN IN H2S, H2TE, AND THE HYDROHALIC
ACIDS. HOWEVER, DAVY FAILED TO DEVELOP A NEW THEORY,
CONCLUDING THAT "ACIDITY DOES NOT DEPEND UPON ANY
PARTICULAR ELEMENTARY SUBSTANCE, BUT UPON PECULIAR
ARRANGEMENT OF VARIOUS SUBSTANCES".[2] ONE NOTABLE
MODIFICATION OF OXYGEN THEORY WAS PROVIDED BY BERZELIUS,
WHO STATED THAT ACIDS ARE OXIDES OF NONMETALS WHILE BASES
ARE OXIDES OF METALS.
Lavoisier's
oxygen
theory
of acids

4. CIRCA 1838 JUSTUS VON
LIEBIG PROPOSED[3] THAT AN ACID IS A
HYDROGEN-CONTAINING SUBSTANCE IN
WHICH THE HYDROGEN COULD BE
REPLACED BY A METAL.[4] THIS
REDEFINITION WAS BASED ON HIS
EXTENSIVE WORK ON THE CHEMICAL
COMPOSITION OF ORGANIC ACIDS,
FINISHING THE DOCTRINAL SHIFT FROM
OXYGEN-BASED ACIDS TO HYDROGEN-
BASED ACIDS STARTED BY DAVY. LIEBIG'S
DEFINITION, WHILE COMPLETELY
EMPIRICAL, REMAINED IN USE FOR
ALMOST 50 YEARS UNTIL THE ADOPTION
OF THE ARRHENIUS DEFINITION
Liebig's
hydrogen theory of
acids

5. THE FIRST MODERN DEFINITION OF ACIDS AND BASES WAS
DEVISED BY SVANTE ARRHENIUS. A HYDROGEN THEORY OF
ACIDS, IT FOLLOWED FROM HIS 1884 WORK WITH FRIEDRICH
WILHELM OSTWALD IN ESTABLISHING THE PRESENCE OF IONS
IN AQUEOUS SOLUTION AND LED TO ARRHENIUS RECEIVING
THE NOBEL PRIZE IN CHEMISTRY IN 1903.
AS DEFINED BY ARRHENIUS:
AN ARRHENIUS ACID IS A SUBSTANCE THAT DISSOCIATES IN
WATER TO FORM HYDROGEN IONS (H+);[6]THAT IS, AN ACID
INCREASES THE CONCENTRATION OF H+ IONS IN AN AQUEOUS
SOLUTION.
THIS CAUSES THE PROTONATION OF WATER, OR THE
CREATION OF THE HYDRONIUM (H3O+) ION.[9] THUS, IN
MODERN TIMES, THE USE OF H+ IS REGARDED AS A
SHORTHAND FOR H3O+, BECAUSE IT IS NOW KNOWN THAT A
BARE PROTON DOES NOT EXIST AS A FREE SPECIES IN
AQUEOUS SOLUTION.[10]
AN ARRHENIUS BASE IS A SUBSTANCE THAT DISSOCIATES IN
WATER TO FORM HYDROXIDE (OH−) IONS; THAT IS, A BASE
INCREASES THE CONCENTRATION OF OH− IONS IN AN
AQUEOUS SOLUTION.
Arrhenius definition
Common acid–base
theories

6. The Arrhenius definitions of acidity and alkalinity are restricted to aqueous
solutions, and refer to the concentration of the solvent ions. Under this definition,
pure H2SO4 and HCl dissolved in toluene are not acidic, and molten NaOH and
solutions of calcium amide in liquid ammonia are not alkaline.
The universal aqueous acid–base definition of the Arrhenius concept is described
as the formation of a water molecule from a proton and hydroxide ion. This leads to
the definition that in Arrhenius acid–base reactions, a salt and water are formed
from the reaction between an acid and a base.[6] This is a neutralization reaction -
the acid and base properties of H+ and OH− are neutralized, for they combine to
form H2O, the water molecule. The acid-base neutralization reaction can be put
into a word equation:
acid + base → salt + water
The positive ion from a base and the negative ion from an acid form a salt together
- in other words, an acid-base neutralization reaction is a double-replacement
reaction. For example, when a neutralization reaction takes place
between hydrochloric acid (HCl) and sodium hydroxide (NaOH), the products
are sodium chloride (common table salt) and water.
HCl(aq) + NaOH(aq) → NaCl + H2O
Notice how the cations and the anions merely switched places: the Na+ from the
NaOH combined with the Cl- from the HCl to form NaCl, while the OH− from the
NaOH combined with the H+ from the HCl to form H2O.

7. The hydrogen requirement of Arrhenius
and Brønsted–Lowry was removed by the
Lewis definition of acid–base reactions,
devised byGilbert N. Lewis in 1923,[16] in
the same year as Brønsted–Lowry, but it
was not elaborated by him until
1938.[2] Instead of defining acid–base
reactions in terms of protons or other
bonded substances, the Lewis definition
defines a base (referred to as a Lewis
base) to be a compound that can donate
an electron pair, and an acid (a Lewis acid)
to be a compound that can receive this
electron pair.[17]
In this system, an acid does not exchange
atoms with a base, but combines with it.
For example, consider this classical
aqueous acid–base reaction:
Lewis definition

8. HCL (AQ) + NAOH (AQ) → H
2O (L) + NACL (AQ)THE LEWIS DEFINITION DOES NOT REGARD THIS REACTION AS THE
FORMATION OF SALT AND WATER OR THE TRANSFER OF H+
FROM HCL TO OH−
. INSTEAD, IT REGARDS THE ACID TO BE THE H+
ION ITSELF, AND THE BASE TO BE THE OH−
ION, WHICH HAS AN UNSHARED ELECTRON PAIR. THEREFORE, THE ACID–BASE
REACTION HERE, ACCORDING TO THE LEWIS DEFINITION, IS THE DONATION OF THE
ELECTRON PAIR FROM OH−
TO THE H+
ION. THIS FORMS A COVALENT BOND BETWEEN H+
AND OH−
, THUS PRODUCING WATER (H
2O).
BY TREATING ACID–BASE REACTIONS IN TERMS OF ELECTRON PAIRS INSTEAD OF
SPECIFIC SUBSTANCES, THE LEWIS DEFINITION CAN BE APPLIED TO REACTIONS THAT DO
NOT FALL UNDER OTHER DEFINITIONS OF ACID–BASE REACTIONS. FOR EXAMPLE, A
SILVER CATION BEHAVES AS AN ACID WITH RESPECT TO AMMONIA, WHICH BEHAVES AS A
BASE, IN THE FOLLOWING REACTION:
AG+
+ 2 :NH
3 → [H
3N:AG:NH
3]+

9. THE RESULT OF THIS REACTION IS THE FORMATION OF AN AMMONIA–SILVER ADDUCT.
IN REACTIONS BETWEEN LEWIS ACIDS AND BASES, THERE IS THE FORMATION OF AN
ADDUCT[17] WHEN THE HIGHEST OCCUPIED MOLECULAR ORBITAL (HOMO) OF A
MOLECULE, SUCH AS NH
3 WITH AVAILABLE LONE ELECTRON PAIR(S) DONATES LONE PAIRS OF ELECTRONS TO
THE ELECTRON-DEFICIENT MOLECULE'S LOWEST UNOCCUPIED MOLECULAR ORBITAL
(LUMO) THROUGH A CO-ORDINATE COVALENT BOND; IN SUCH A REACTION, THE
HOMO-INTERACTING MOLECULE ACTS AS A BASE, AND THE LUMO-INTERACTING
MOLECULE ACTS AS AN ACID.[17] IN HIGHLY-POLAR MOLECULES, SUCH AS BORON
TRIFLUORIDE(BF
3),[17] THE MOST ELECTRONEGATIVE ELEMENT PULLS ELECTRONS TOWARDS ITS OWN
ORBITALS, PROVIDING A MORE POSITIVE CHARGE ON THE LESS-ELECTRONEGATIVE
ELEMENT AND A DIFFERENCE IN ITS ELECTRONIC STRUCTURE DUE TO THE AXIAL OR
EQUATORIAL ORBITING POSITIONS OF ITS ELECTRONS, CAUSING REPULSIVE EFFECTS
FROM LONE PAIR – BONDING PAIR (LP–BP) INTERACTIONS BETWEEN BONDED ATOMS
IN EXCESS OF THOSE ALREADY PROVIDED BY BONDING PAIR – BONDING PAIR (BP–
BP) INTERACTIONS.[17] ADDUCTS INVOLVING METAL IONS ARE REFERRED TO AS CO-
ORDINATION COMPOUNDS

10. THIS ACID–BASE THEORY WAS A REVIVAL OF OXYGEN THEORY
OF ACIDS AND BASES, PROPOSED BY GERMAN
CHEMIST HERMANN LUX[18][19] IN 1939, FURTHER IMPROVED
BY HÅKON FLOOD CIRCA 1947[20] AND IS STILL USED IN
MODERN GEOCHEMISTRY AND ELECTROCHEMISTRY OF MOLTEN
SALTS. THIS DEFINITION DESCRIBES AN ACID AS AN OXIDE ION
(O2−
) ACCEPTOR AND A BASE AS AN OXIDE ION DONOR. FOR
EXAMPLE:[21]
MGO (BASE) + CO
2 (ACID) → MGCO
3CAO (BASE) + SIO
2 (ACID) → CASIO
3NO−
3 (BASE) + S
2O2−
7 (ACID) → NO+
2 + 2 SO2−
4
Lux–Flood
definition
Other
acid–base
theories

11. IN 1963,[22] RALPH PEARSON PROPOSED
AN ADVANCED QUALITATIVE CONCEPT
KNOWN AS HARD SOFT ACID BASE
PRINCIPLE, LATER MADE QUANTITATIVE
WITH HELP OF ROBERT PARR IN 1984.
'HARD' APPLIES TO SPECIES THAT ARE
SMALL, HAVE HIGH CHARGE STATES, AND
ARE WEAKLY POLARIZABLE. 'SOFT' APPLIES
TO SPECIES THAT ARE LARGE, HAVE LOW
CHARGE STATES AND ARE STRONGLY
POLARIZABLE. ACIDS AND BASES INTERACT,
AND THE MOST STABLE INTERACTIONS ARE
HARD–HARD AND SOFT–SOFT. THIS
THEORY HAS FOUND USE IN ORGANIC AND
INORGANIC CHEMISTRY.
Pearson
definition

12. MIKHAIL USANOVICH DEVELOPED A GENERAL THEORY THAT DOES
NOT RESTRICT ACIDITY TO HYDROGEN-CONTAINING COMPOUNDS,
BUT HIS APPROACH, PUBLISHED IN 1938, WAS EVEN MORE GENERAL
THAN LEWIS THEORY.[2] USANOVICH'S THEORY CAN BE SUMMARIZED
AS DEFINING AN ACID AS ANYTHING THAT ACCEPTS NEGATIVE
SPECIES OR DONATES POSITIVE ONES, AND A BASE AS THE
REVERSE. THIS DEFINED THE CONCEPT OF REDOX (OXIDATION-
REDUCTION) AS A SPECIAL CASE OF ACID-BASE REACTIONS
SOME EXAMPLES OF USANOVICH ACID-BASE REACTIONS INCLUDE:
NA
2O (BASE) + SO
3 (ACID) → 2 NA+
+ SO2−
4 (SPECIES EXCHANGED: ANION O2−
)3 (NH
4)
2S (BASE) + SB
2S
3 (ACID) → 6 NH+
4 + 2 SBS3−
4 (SPECIES EXCHANGED: ANION S2−
)NA (BASE) + CL (ACID) → NA+
+ CL−
(SPECIES EXCHANGED: ELECTRON)
Usanovich
definition

13.  An acid–alkali reaction is a special case of an acid–base reaction, where the base used
is also an alkali. When an acid reacts with an alkali it forms a metal salt and water. Acid–
alkali reactionsAcid–alkali reaction
 are also a type of neutralization reaction.
 In general, acid–alkali reactions can be simplified to
 OH−
(aq) + H+
(aq) → H
2Oby omitting spectator ions.
 Acids are in general pure substances that contain hydrogen ions (H+
) or cause them to be produced in solutions. Hydrochloric acid (HCl) and sulfuric acid (H
2SO
4) are common examples. In water, these break apart into ions:
 HCl → H+
(aq) + Cl−
(aq)H
2SO
4 → H+
(aq) + HSO−
4(aq)To produce hydroxide ions in water, the alkali breaks apart into ions as below:
 NaOH → Na+
(aq) + OH−
Acid–alkali reaction