Download 1 - Intro to Electrochemistry

SCH4U – Electrochemistry
493699228
Date: ________________________
Introduction to Electrochemistry
A redox reaction is one where one substance is _______________ while another
substance is simultaneously _______________
Oxidation
Oxidation occurs when a substance _________ electrons during a chemical reaction
Its oxidation number _____________________ (more on this later)
Example: Cu(s)  Cu2+ + 2 eReduction
During reduction, a substance ____________ electrons during a chemical reaction
The oxidation number of the substance being reduced is ______________ in the
chemical reaction
Example: Ag+ + e-  Ag(s)
Consider:
Zn(s) + CuSO4(aq) → Cu(s) + ZnSO4(aq)
Write out the total and net ionic equations
Oxidizing Agent
An oxidizing agent is a substance that causes another substance to be __________
For example, in the reaction:
2 Ag+ + Cu(s)  2 Ag(s) + Cu2+
Ag+ is the oxidization agent because it causes Cu to be ______________. Ag+ itself
is ___________________
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SCH4U – Electrochemistry
493699228
Reducing Agent
A reducing agent causes another substance to be ____________________
It is ________________ in the process
2 Ag+ + Cu(s)  2 Ag(s) + Cu2+
Cu(s) is the reducing agent as it causes Ag+ to be __________________
Oxidation Numbers
Oxidation Numbers are the ___________ or ________________ charge that an
element exhibits when it is part of a compound or ion
Examples:
NaCl
CCl4
In ionic compounds, the assignment of oxidation numbers is relatively simple since
electrons are _________________ from one atom to another to form the compound
Example: NiCl2
In covalent compounds however, electrons are not really ____________________
Instead, _____________________ result from the _______________________ of
the electrons involved in the covalent bond
In covalent compounds, the _________________ oxidation number is arbitrarily
assigned to the element having the greatest _________________________
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SCH4U – Electrochemistry
493699228
Rules for Oxidation Numbers
1. Any pure element has an oxidation number of ___________
2. The oxidation number of a monoatomic ion equals the ________________________
3. The sum of the oxidation numbers in a neutral compound is ___________
4. The sum of the oxidation numbers in a polyatomic ion is equal to the charge
________________________________
5. The oxidation number of oxygen is always _____ except in peroxides where it is
_____ and when bonded to fluorine, it has a charge of _____
6. The oxidation number of hydrogen is always _____ except in metal hydrides where it
is _____
Examples:
Na3PO4
CaH2
PCl3
Homework
SnCl4
Sn
____
Cl
____
Ca3P2
Ca ____
P
____
SnO
Sn
____
O
____
Ag2S
Ag
____
S
____
HI
H
____
I
____
N2H4
N
____
H
____
Al2O3
Al
____
O
____
S8
S
____
HNO2
H
____
N
____
O2
O
____
H3O+
H
____
O
____
ClO3-
Cl
____
O
____
S2O32-
S
____
O
____
KMnO4
K
____
(NH4)2SO4
N
____
O
____
Mn ____
O
____
H
S
____
____
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O
____
SCH4U – Electrochemistry
493699228
Answers
SnCl4
Sn
__+4__ Cl
__-1__
Ca3P2
Ca __+2__ P
__-3__
SnO
Sn
__+2__ O
__-2__
Ag2S
Ag
__+1__ S
__-2__
HI
H
__+1__ I
__-1__
N2H4
N
__-2__ H
__+1__
Al2O3
Al
__+3__ O
__-2__
S8
S
__0__
HNO2
H
__+1__ N
O2
O
__0__
H3O+
H
__+1__ O
__-2__
ClO3-
Cl
__+5__ O
__-2__
S2O32-
S
__+2__ O
__-2__
KMnO4
K
__+1__ Mn __+7__ O
__-2__
(NH4)2SO4
N
__-3__ H
__+6__ O
__+3__ O
__+1__ S
__-2__
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__-2__