Redox Reactivity and Balancing Equations in Acidic Solutions
QUESTION
QUESTION
Z
i
n
c
Reactivity Tables
(usually reducing)
show relative
reactivities:
In the examples from
the previous slide, the
acid solution (H
+
) will
react with anything
below it in the Table
but not above.
Nickel and Zinc,
….but not Copper.
Cu
2+
Cu
(s)
H
2
(g)
2 H
+
0
0
+2 e-
- 2 e-
Use oxidation numbers to determine what is oxidized
and what is reduced.
Number of electrons gained must equal the number of electrons lost.
- 2 e-
+2 e-
Refer to Balancing
Oxidation-Reduction Reactions
QUESTION
QUESTION
Balancing Redox Equations
in acidic solutions
1) Determine the oxidation numbers of atoms in both
reactants and products.
2) Identify and select out those which change
oxidation number (
“
redox
”
atoms) into separate
“
half reactions
”
.
3) Balance the
“
redox
”
atoms and charges (electron
gain and loss must equal!).
4) In acidic reactions balance oxygen with water
then hydrogen from water with acid proton(s).
F
F
e
e
+
+
2
2
(
(
a
a
q
q
)
)
+
+
C
C
r
r
2
2
O
O
7
7
2
2
-
-
(
(
a
a
q
q
)
)
+
+
H
H
+
+
(
(
a
a
q
q
)
)
F
F
e
e
3
3
+
+
(
(
a
a
q
q
)
)
+
+
C
C
r
r
3
3
+
+
(
(
a
a
q
q
)
)
+
+
H
H
2
2
O
O
(
(
l
l
)
)
F
F
e
e
2
2
+
+
(
(
a
a
q
q
)
)
+
+
C
C
r
r
2
2
O
O
7
7
2
2
-
-
(
(
a
a
q
q
)
)
+
+
H
H
+
+
(
(
a
a
q
q
)
)
F
F
e
e
3
3
+
+
(
(
a
a
q
q
)
)
+
+
C
C
r
r
3
3
+
+
(
(
a
a
q
q
)
)
+
+
H
H
2
2
O
O
(
(
l
l
)
)
x
x
=
=
?
?
C
C
r
r
;
;
2
2
x
x
+
+
7
7
(
(
-
-
2
2
)
)
=
=
-
-
2
2
;
;
x
x
=
=
+
+
6
6
? Cr oxidation number?
? Cr oxidation number?
Balancing Redox Equations
Balancing Redox Equations
in acidic solutions
in acidic solutions
F
F
e
e
2
2
+
+
(
(
a
a
q
q
)
)
F
F
e
e
3
3
+
+
(
(
a
a
q
q
)
)
C
C
r
r
2
2
O
O
7
7
2
2
-
-
(
(
a
a
q
q
)
)
+
+
C
C
r
r
3
3
+
+
(
(
a
a
q
q
)
)
C
C
r
r
=
=
(
(
6
6
+
+
)
)
6
6
(
(
F
F
e
e
2
2
+
+
(
(
a
a
q
q
)
)
-
-
e
e
-
-
F
F
e
e
3
3
+
+
(
(
a
a
q
q
)
)
)
)
6
6
F
F
e
e
2
2
+
+
(
(
a
a
q
q
)
)
6
6
F
F
e
e
3
3
+
+
(
(
a
a
q
q
)
)
+
+
6
6
e
e
-
-
C
C
r
r
2
2
O
O
7
7
2
2
-
-
(
(
a
a
q
q
)
)
+
+
6
6
e
e
-
-
2
2
C
C
r
r
3
3
+
+
(
(
a
a
q
q
)
)
6
6
e
e
-
-
-
-
e
e
-
-
2
2
Balancing Redox Equations
Balancing Redox Equations
in acidic solutions
in acidic solutions
6
6
F
F
e
e
2
2
+
+
(
(
a
a
q
q
)
)
6
6
F
F
e
e
3
3
+
+
(
(
a
a
q
q
)
)
+
+
6
6
e
e
-
-
C
C
r
r
2
2
O
O
7
7
2
2
-
-
(
(
a
a
q
q
)
)
+
+
6
6
e
e
-
-
2
2
C
C
r
r
3
3
+
+
(
(
a
a
q
q
)
)
6
6
F
F
e
e
2
2
+
+
(
(
a
a
q
q
)
)
+
+
C
C
r
r
2
2
O
O
7
7
2
2
-
-
(
(
a
a
q
q
)
)
+
+
?
?
2
2
n
n
d
d
H
H
+
+
(
(
a
a
q
q
)
)
6
6
F
F
e
e
3
3
+
+
(
(
a
a
q
q
)
)
+
+
2
2
C
C
r
r
3
3
+
+
(
(
a
a
q
q
)
)
+
+
?
?
1
1
s
s
t
t
O
O
x
x
y
y
g
g
e
e
n
n
H
H
2
2
O
O
(
(
l
l
)
)
O
O
x
x
y
y
g
g
e
e
n
n
=
=
7
7
2
2
n
n
d
d
(
(
H
H
y
y
d
d
r
r
o
o
g
g
e
e
n
n
)
)
=
=
1
1
4
4
Balancing Redox Equations
Balancing Redox Equations
in acidic solutions
in acidic solutions
C
C
o
o
m
m
p
p
l
l
e
e
t
t
e
e
l
l
y
y
B
B
a
a
l
l
a
a
n
n
c
c
e
e
d
d
E
E
q
q
u
u
a
a
t
t
i
i
o
o
n
n
:
:
6
6
F
F
e
e
2
2
+
+
(
(
a
a
q
q
)
)
+
+
C
C
r
r
2
2
O
O
7
7
2
2
-
-
(
(
a
a
q
q
)
)
+
+
1
1
4
4
H
H
+
+
(
(
a
a
q
q
)
)
6
6
F
F
e
e
3
3
+
+
(
(
a
a
q
q
)
)
+
+
2
2
C
C
r
r
3
3
+
+
(
(
a
a
q
q
)
)
+
+
7
7
H
H
2
2
O
O
(
(
l
l
)
)
Balancing Redox Equations
Balancing Redox Equations
in acidic solutions
in acidic solutions
Balancing Redox Equations
Balancing Redox Equations
in basic solutions
in basic solutions
1) Determine oxidation numbers of atoms in
1) Determine oxidation numbers of atoms in
Reactants and Products
Reactants and Products
2) Identify and select out those which change
2) Identify and select out those which change
oxidation number into separate
oxidation number into separate
“
“
half reactions
half reactions
”
”
3) Balance redox atoms and charges (electron gain
3) Balance redox atoms and charges (electron gain
and loss must equal!)
and loss must equal!)
4) In basic reactions balance the Oxygen with
4) In basic reactions balance the Oxygen with
hydroxide then Hydrogen from hydroxide with
hydroxide then Hydrogen from hydroxide with
water
water
M
M
n
n
O
O
2
2
(
(
a
a
q
q
)
)
+
+
C
C
l
l
O
O
3
3
1
1
-
-
(
(
a
a
q
q
)
)
+
+
O
O
H
H
1
1
-
-
a
a
q
q
)
)
M
M
n
n
O
O
4
4
1
1
-
-
(
(
a
a
q
q
)
)
+
+
C
C
l
l
1
1
-
-
(
(
a
a
q
q
)
)
+
+
H
H
2
2
O
O
(
(
l
l
)
)
M
M
n
n
4
4
+
+
(
(
M
M
n
n
O
O
2
2
)
)
M
M
n
n
7
7
+
+
(
(
M
M
n
n
O
O
4
4
)
)
1
1
-
-
C
C
l
l
+
+
5
5
(
(
C
C
l
l
O
O
3
3
)
)
1
1
-
-
+
+
6
6
e
e
-
-
C
C
l
l
1
1
-
-
Balancing Redox Equations
Balancing Redox Equations
in basic solutions
in basic solutions
Electronically Balanced Equation:
Electronically Balanced Equation:
2
2
M
M
n
n
O
O
2
2
(
(
a
a
q
q
)
)
+
+
C
C
l
l
O
O
3
3
1
1
-
-
(
(
a
a
q
q
)
)
+
+
6
6
e
e
-
-
2
2
M
M
n
n
O
O
4
4
1
1
-
-
+
+
C
C
l
l
1
1
-
-
+
+
6
6
e
e
-
-
Balancing Redox Equations
in basic solutions
Completely Balanced Equation:
Completely Balanced Equation:
2
2
M
M
n
n
O
O
2
2
(
(
a
a
q
q
)
)
+
+
C
C
l
l
O
O
3
3
1
1
-
-
(
(
a
a
q
q
)
)
+
+
2
2
O
O
H
H
1
1
-
-
(
(
a
a
q
q
)
)
2
2
M
M
n
n
O
O
4
4
(
(
a
a
q
q
)
)
1
1
-
-
+
+
C
C
l
l
1
1
-
-
(
(
a
a
q
q
)
)
+
+
1
1
H
H
2
2
O
O
(
(
l
l
)
)
9
9
O
O
i
i
n
n
p
p
r
r
o
o
d
d
u
u
c
c
t
t
Balancing Redox Equations
Balancing Redox Equations
in basic solutions
in basic solutions
Exploring the concept of reactivity in redox reactions using zinc, nickel, and copper, followed by a detailed guide on balancing redox equations in acidic solutions. Learn how to determine oxidation numbers, identify redox atoms, balance charges, and handle oxygen and hydrogen atoms to achieve balanced equations like a pro.
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Presentation Transcript
Reactivity Tables (usually reducing) show relative reactivities: In the examples from the previous slide, the acid solution (H+) will react with anything below it in the Table but not above. Nickel and Zinc, .but not Copper.
Number of electrons gained must equal the number of electrons lost. - 2 e- +2 e- Use oxidation numbers to determine what is oxidized and what is reduced. +2 e- 0 0 Cu 2+ Cu (s) - 2 e- 2 H + H2(g) Refer to Balancing Oxidation-Reduction Reactions
Balancing Redox Equations in acidic solutions 1) Determine the oxidation numbers of atoms in both reactants and products. 2) Identify and select out those which change oxidation number ( redox atoms) into separate half reactions . 3) Balance the redox atoms and charges (electron gain and loss must equal!). 4) In acidic reactions balance oxygen with water then hydrogen from water with acid proton(s). 1
Balancing Redox Equations in acidic solutions 1 Fe+2(aq)+ Cr2O72-(aq) +H+(aq) Fe3+(aq) + Cr3+(aq) + H2O(l) Fe 2+(aq)+ Cr2O72-(aq) +H+(aq) Fe 3+(aq) + Cr 3+(aq) + H2O(l) ? Cr oxidation number? x = ? Cr ; 2x+7(-2) = -2; x = +6
Balancing Redox Equations in acidic solutions 1 -e - Fe 2+(aq) Fe 3+(aq) Cr2O72-(aq) + Cr 3+(aq) Cr = (6+) 6 (Fe 2+(aq) -e - Fe3+(aq)) 6 Fe 2+(aq) 6 Fe3+(aq) + 6 e - Cr2O72-(aq) + 6 e - 2 Cr3+(aq) 2 6 e -
Balancing Redox Equations in acidic solutions 1 6 Fe2+(aq) 6 Fe3+(aq) + 6 e - Cr2O72-(aq) + 6 e - 2 Cr3+(aq) 6 Fe2+(aq)+ Cr2O72-(aq) + ? 2nd H+(aq) 6 Fe3+(aq) + 2 Cr3+(aq)+ ? 1st Oxygen H2O(l) Oxygen = 7 2nd (Hydrogen) = 14
Balancing Redox Equations in acidic solutions 1 Completely Balanced Equation: 6 Fe2+(aq)+ Cr2O72-(aq) + 14 H+(aq) 6 Fe3+(aq) + 2 Cr3+(aq)+ 7H2O(l)
Balancing Redox Equations in basic solutions 1 1) Determine oxidation numbers of atoms in Reactants and Products 2) Identify and select out those which change oxidation number into separate half reactions 3) Balance redox atoms and charges (electron gain and loss must equal!) 4) In basic reactions balance the Oxygen with hydroxide then Hydrogen from hydroxide with water
Balancing Redox Equations in basic solutions MnO2 (aq)+ ClO31-(aq) + OH 1-aq) MnO41- (aq)+ Cl 1-(aq) + H2O(l) Mn4+ (MnO2) Mn7+ (MnO4 ) 1- Cl+5 (ClO3 ) 1-+ 6 e- Cl 1-
Balancing Redox Equations in basic solutions Electronically Balanced Equation: 2 MnO2 (aq)+ ClO31-(aq) + 6e - 2 MnO4 1- + Cl 1- + 6 e-
Balancing Redox Equations in basic solutions Completely Balanced Equation: 2 MnO2 (aq)+ ClO31-(aq) + 2OH 1- (aq) 2 MnO4 (aq)1- + Cl 1- (aq)+ 1 H2O (l) 9 O in product
