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General Chemistryt 2 WEEK 5
CHEM 2 M5
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BS Criminology (CLJ 1)
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Northern Philippines College for Maritime, Science and Technology
Mc. Arthur Highway, Lingsat, City of San Fernando, La Union
HIGH SCHOOL DEPARTMENT
GENERAL CHEMISTRY 2
Name: Score:
Section:
General
Chemistry 2
Quarter 4 – Week 5 - Module 5
Redox Reactions
TARGET
We are now in a current generation where digital learning is
encouraged for a better learning process and is accomplished through the use of
gadgets What gadget is not powered by batteries or a cell function? Likewise, we
often encounter antioxidants as popular products today and the marketability is
high for the marketers use the ability of their products to effectively prevent and
counteract the effects of oxidant pollutants in the environment. Furthermore,
everyday redox reactions occur like photosynthesis, respiration, combustion and
corrosion.
The principles behind the creation of these electrochemical reactions, are
bounded into the branch of chemistry which is electrochemistry. It is a study of the
relationship between electron flow and redox reactions. It is concerned with the
study of chemical reactions that either produce or are driven by electrical energy.
This module serves as an introduction for a better understanding of the
electrochemical reactions mentioned. It is best therefore, to start with a discussion
of oxidation reduction reactions.
After going through this module, you are expected to:
1) Define oxidation and reduction. (STEM_GC11ABIVf-g-169)
2) Identify the substance which is reduced and oxidized in
chemical equation
3) Determine whether the chemical reaction is a redox reaction
4) Balance redox reactions using the change in oxidation number
method. (STEM_GC11ABIVf-g-170)
REMEMBER!!!
Oxidizing agent – substance reduced; undergoes a decrease in oxidation number
Reducing agent – substance oxidized; undergoes an increase in oxidation number
DON’T INTERCHANGE!!! The substance that is reduced in a reaction is the oxidizing agent because it
gains electrons. The substance that is oxidized in a reaction is the reducing agent because it lost
electrons.
Although reduction and oxidation take place simultaneously, it is often
convenient to consider them as separate processes and can be presented as two
half reactions. Hence this reduction may be written as:
Cu 2 +(aq) + 2e- → Cu(s) Zn(s) → Zn2+(aq) + 2e-
Reduction of Cu2+(aq) Oxidation of Zn (s)
Furthermore, the substance that makes it possible for another substance to
be oxidized is called the oxidizing agent or oxidant. The oxidizing agent requires the
electrons from another substance, causing it to be reduced. On the other hand, the
reducing agent or reductant is oxidized in the process by giving up its electrons to
the substance it will reduce.
For example:
2Mg(s) + O2( g) → 2MgO(s)
In the burning of Mg , O 2 is reduced by losing oxygen atoms. Thus,
O 2 is an oxidizing agent as it undergoes reduction.
4NH 3 + 5O 2 → 4NO + 6H 2 O
In the given reaction, Nitrogen is oxidized to NO by gaining oxygen atom. Thus, NH 3
is reducing agent as it undergoes oxidation.
For you to understand better about the oxidizing agent and reduction
agent, the activity below is given to test and further widen your knowledge about
the said topic.
Determine whether the underlined element is oxidized or reduced in a
given partial equation and state if it is an oxidizing agent or a reducing agent
1. H 2 O 2 → O 2
2. KBrO 3 → KBr
3. Fe + FeSO 4 → Fe 2 (SO 4 ) 3
4. Na 2 C 2 O 4 → CO 2
5. I 2 → KI
Given equation :
Fe 2 O 3 (s)+CO(g)→Fe(s)+CO 2 (g)
DISCOVER
Oxidation Number is a concept that helps in determining quickly whether the
substance is undergoing oxidation or reduction. Other terms used to refer to
oxidation number is valence or oxidation state. Oxidation states is the electrical
charge assigned to an atom according to a prescribed set of rules. It can be
computed directly from the formula itself based on the following guidelines:
1. The oxidation state of a free and uncombined element is zero. E. Mg 0 , H 20 ,
S 80 , C0.
2. The usual oxidation state of:
a. Hydrogen is +1, except in metallic hydrides ( Li+1, H-1 )
b. Oxygen is -2, except in peroxides where it is -1 ( H 2 -1 , O 2 -1 )
c. Elements under group IA is +1, IIA is +2, and IIIA is +3.( Na+1, Mg+2,
Al+3)
3. In a compound, the algebraic sum of the total positive and negative
oxidation number is always equal to zero.
Example: In KClO 3 , the oxidation state of K = +1 and O = -
Let x = oxidation state of Cl
Upon substitution: +1 + x + (3) (-2) = 0
+1 + x – 6 = 0
X = +
4. The algebraic sum of the positive and negative oxidation states of all atoms
in ion is equal to the charge of the ion.
Example: In ClO 3 -1, the oxidation state of O is -
Let x = oxidation state of Cl
Upon substitution: x – (3) (-2) = - 1
x + 6 = - 1
x = +
Note that the oxidation number of Cl, whether it is in the compound KClO 3 ,
or in ClO 3 -1 ion is the same as, +5.
To determine whether the chemical reaction is an oxidation reduction
reaction, assign the oxidation state of each element and find out if there are
elements that undergo changes in oxidation number.
Balancing Redox Reactions
There are two ways of balancing oxidation reductions reactions. The first method is
based on the change in oxidation number while the second method is the ion-
electron method.
A. Balancing by oxidation number method
EXPLORE
The following practice problems are prepared for you to
polish and enrich your understanding in determining the oxidizing state of
elements and further widen your understanding about the differences between
an oxidizing agent and a reducing agent.
Good Luck and Have Fun!
Exercise:
I. Assign oxidation state to the underlined element.
1) Cl 2
2) SO 2
3) K 2 O 2
4) Cr 2 O 7 - 2
5) Na 2 O 2
6) Na 2 S 2 O 3
7) NaN 3
8) CH 4
9) Fe 203
10) MnO 2
II. Identify oxidizing agent and reducing agent in the reactions.
1. 2Na 2 S 2 O 3 + I 2 → Na 2 S 4 O 6 + 2NaI
2. N 2 + 3H 2 → 2NH 3
3. 2FeCl 3 + H 2 S → 2FeCl 2 + S + 2HCl
4. 2 Cr3+ +H 2 O+ 6ClO 3 - → Cr 2 O 7 2- +6ClO 2 + 2H+
5. 3Mg + N 2 → Mg 3 N 2
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General Chemistryt 2 WEEK 5
Course: BS Criminology (CLJ 1)
10 Documents
Students shared 10 documents in this course
Was this document helpful?
1
Northern Philippines College for Maritime, Science and Technology
Mc. Arthur Highway, Lingsat, City of San Fernando, La Union
HIGH SCHOOL DEPARTMENT
GENERAL CHEMISTRY 2
Name: Score:
Section:
General
Chemistry
2
Quarter 4 – Week 5 - Module 5
Redox Reactions
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