Oxidizing And

Reducing Agents
Industrial Applications

Sayed Hassan Ali Shah

13-06-2019

inzmamsanaullah@gmail.com
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Chemical stoichiometry
Stoichiometry Definition. Stoichiometry is the study of the quantitative relationships or ratios
between two or more substances undergoing a physical change or chemical change
(chemical reaction). The word derives from the Greek words: stoicheion (meaning "element")
and metron (meaning "to measure").

What are oxidation numbers?

Chemists use oxidation numbers (or oxidation states) to keep track of how
many electrons an atom has. Oxidation numbers don’t always correspond to
real charges on molecules, and we can calculate oxidation numbers for atoms
that are involved in covalent (as well as ionic) bonding.

Let's make sense of oxidation numbers with a few examples!

Guidelines for determining the oxidation

number
Oxidation numbers are usually written with the sign (++plus or -−minus)
first, then the magnitude, which is the opposite of charges on ions. Chemists
use the following guidelines to determine oxidation numbers:
Step 1.~1. 1, point, spaceAtoms in their elemental state have an oxidation
number of 000.

Step 2.~2. 2, point, spaceAtoms in monatomic (i.e. single atom) ions have an
oxidation number equal to their charge.
Step 3.~3. 3, point, spaceIn compounds: fluorine is assigned a −1 oxidation
number; oxygen is usually assigned a −2 oxidation number (except in
peroxide compounds where it is −1, and in binary compounds with fluorine
where it is positive); and hydrogen is usually assigned a +1+1plus,
1 oxidation number except when it exists as the hydride ion, H−, in which
case rule 222 wins.

Step 4.~4. 4, point, spaceIn compounds, all other atoms are assigned an
oxidation number so that the sum of the oxidation numbers on all the atoms
in the species equals the charge on the species.

Oxidation Definition
Oxidation is the loss of electrons during a reaction by
a molecule, atom or ion.

Oxidation occurs when the oxidation state of a molecule, atom or

ion is increased. The opposite process is called reduction, which
occurs when there is a gain of electrons or the oxidation state of
an atom, molecule, or ion decreases.

An example of a reaction is that between hydrogen and fluorine

gas to form hydrofluoric acid:

H2 + F2 → 2 HF
In this reaction, hydrogen is being oxidized and fluorine is being
reduced. The reaction may be better understood if it is written in
terms of two half-reactions.

H2 → 2 H+ + 2 e-

F2 + 2 e- → 2 F-

Note there is no oxygen anywhere in this reaction!

Reduction

Reduction involves a half-reaction in which a chemical species

decreases its oxidation number, usually by gaining electrons. The
other half of the reaction involves oxidation, in which electrons
are lost. Together, reduction and oxidation form redox reactions
(reduction-oxidation = redox). Reduction may be considered the
opposite process of oxidation.

Redox (short for reduction–oxidation reaction) is a type of chemical reaction in

which the oxidation states of atoms are changed. Redox reactions are
characterized by the transfer of electrons between chemical species, most often
with one species (the reducing agent) undergoing oxidation (losing electrons)
while another species (the oxidizing agent) undergoes reduction (gains
electrons).[2] The chemical species from which the electron is stripped is said to
have been oxidized, while the chemical species to which the electron is added is
said to have been reduced. In other words:
 Oxidation is the loss of electrons or an increase in the oxidation state of an
atom by a molecule, an ion, or another atom.
 Reduction is the gain of electrons or a decrease in the oxidation state of an
atom by a molecule, an ion, or another atom.

Oxidizing and Reducing Agents

An oxidizing agent, or oxidant, gains electrons and is reduced in a
chemical reaction. Also known as the electron acceptor, the oxidizing agent is
normally in one of its higher possible oxidation states because it will gain
electrons and be reduced. Examples of oxidizing agents include halogens,
potassium nitrate, and nitric acid.
A reducing agent, or reductant, loses electrons and is oxidized in a
chemical reaction. A reducing agent is typically in one of its lower possible
oxidation states, and is known as the electron donor. A reducing agent is
oxidized, because it loses electrons in the redox reaction. Examples of
reducing agents include the earth metals, formic acid, and sulfite compounds.
DEFINITIONS
 A reducing agent reduces other substances and loses electrons;
therefore, its oxidation state increases.
 An oxidizing agent oxidizes other substances and gains electrons;
therefore, its oxidation state decreases
EXAMPLE 1: IDENTIFY REDUCING AND OXIDIZING AGENTS
Identify the reducing and oxidizing agents in the balanced redox reaction:
Cl2(aq)+2Br−(aq)→2Cl−(aq)+Br2(aq)(1)(1)Cl2(aq)+2Br−(aq)→2Cl−(aq)+Br
2(aq)
Oxidation half reaction
2Br−(aq)→Br2(aq)(2)(2)2Br−(aq)→Br2(aq)
Oxidation States: -1 0
Reduction Half Reaction
Cl2(aq)→2Cl−(aq)(3)(3)Cl2(aq)→2Cl−(aq)
Oxidation States: 0 -1
Overview
 B- loses an electron; it is oxidized from Br- to Br2; thus, Br- is
the reducing agent.
 Cl2 gains one electron; it is reduced from Cl2 to 2 Cl-; thus, Cl2 is
the oxidizing agent.
EXERCISE
Identify the oxidizing agent and the reducing agent in the following redox
reaction:
MnO−4+SO2−3→Mn+2+SO2−4(4)(4)MnO4−+SO32−→Mn+2+SO42−
Solution
SS is the reducing agent and MnMn is the oxidizing agent.

Applications
Oxidizing and reducing agents are important in industrial applications. They
are used in processes such as purifying water, bleaching fabrics, and storing
energy (such as in batteries and gasoline). Oxidizing and reducing agents are
especially crucial in biological processes such as metabolism and
photosynthesis. For example, organisms use electron acceptors such as
NAD+ to harvest energy from redox reactions as in the hydrolysis of glucose:
C6H12O6+2ADP+2P+2NAD+→2CH3COCO2H+2ATP+2NADH(1)(1)C6H
12O6+2ADP+2P+2NAD+→2CH3COCO2H+2ATP+2NADH
All combustion reactions are also examples of redox reactions. A combustion
reaction occurs when a substance reacts with oxygen to create heat. One
example is the combustion of octane, the principle component of gasoline:
2C8H18(l)+25O2(g)→16CO2(g)+18H2O(g)(2)(2)2C8H18(l)+25O2(g)→16CO
2(g)+18H2O(g)
Combustion reactions are a major source of energy for modern industry.

 Forming a New Surface on Metal

Clearly, oxidization can have a corrosive effect, and nowhere is this more obvious than
in the corrosion of metals by exposure to oxidizing agents—primarily oxygen itself. Most
metals react with O 2 , and might corrode so quickly that they become useless, were it
not for the formation of a protective coating—an oxide.
Iron forms an oxide, commonly known as rust, but this in fact does little to protect it from
corrosion, because the oxide tends to flake off, exposing fresh surfaces to further
oxidation. Every year, businesses and governments devote millions of dollars to
protecting iron and steel from oxidation by means of painting and other measures, such
as galvanizing with zinc. In fact, oxidation-reduction reactions virtually define the world
of iron. Found naturally only in ores, the element is purified by heating the ore with coke
(impure carbon) in the presence of oxygen, such that the coke reduces the iron.

 The Environment and Human Health

Combustion, though it can do much good, can also do much harm. This goes beyond
the obvious: by burning fossil fuels or hydrocarbons, excess carbon (in the form of
carbon dioxide and carbon monoxide) is released to the atmosphere, with a damaging
effect on the environment.
In fact, oxidation-reduction reactions are intimately connected with the functioning of the
natural environment. For example, photosynthesis, the conversion of light to chemical
energy by plants, is a form of oxidation-reduction reaction that produces two essentials
of human life: oxygen and carbohydrates. Likewise cellular respiration, which along with
photosynthesis is discussed in the Carbon essay, is an oxidation-reduction reaction in
which living things break down molecules of food to produce energy, carbon dioxide,
and water.
Enzymes in the human body regulate oxidation-reduction reactions. These complex
proteins, of which several hundred are known, act as catalysts, speeding up chemical
processes in the body. Oxidation-reduction reactions also take place in the metabolism
of food for energy, with substances in the food broken down into components the body
can use.
Use of Oxidizing Agent in Textile Wet Processing:
1) Desizing:
Desizing is the process or removing the starch or size the covering the warp yarn using enzyme.
Oxidizing agent, or other chemicals . Lastly, is oxidative desizing method. This method using
hydrogen peroxide and persulphate, that will degrade the starch with serious attack.

2) Oxidized Starch:
The starch derivatives made by oxidative processes find limited use in textile sizing because they
are more expensive to produce as compared to the other starch modifications which can give
essentially similar properties to high solids/low viscosity cooks [5]. Instead of using acid to
reduce the starch chain length, sodium hypochlorite, an oxidizing agent, is employed.

3) Bleaching:
Cotton being a vegetable fibre will be bleached using an oxidizing agent.Bleaching is a process
of destruction of natural coloring matter to produce white fabric band be accomplished with a
minimum damage to the cloth being bleached. Cotton being a vegetable fiber will be bleached
using an oxidizing agent, such as dilute sodium hydrochloride or dilute hydrogen peroxide. If the
fabric is to be dyed a deep shade, then lower levels of bleaching are acceptable.
References
https://www.thoughtco.com/definition-of-oxidation-in-chemistry-605456

https://www.khanacademy.org/science/chemistry/chemical-reactions-stoichiome/types-of-chemical-
reactions/a/oxidation-number

https://chem.libretexts.org/Bookshelves/Analytical_Chemistry/Supplemental_Modules_(Analytical_Che
mistry)/Electrochemistry/Redox_Chemistry/Oxidizing_and_Reducing_Agents

https://chem.libretexts.org/Bookshelves/Analytical_Chemistry/Supplemental_Modules_(Analytical_Che
mistry)/Electrochemistry/Redox_Chemistry/Oxidizing_and_Reducing_Agents