Transcript redox reaction reaksi redoks

CHAPTER 6
REDOX REACTION
REAKSI REDOKS
Teaching Learning Objectivers
• The student can explain definition of redox
reactions the first concept (the release and
uptake of atoms concept)
• The student can explain definition of redox
reactions the secon concept (the electrons
transfer concept)
• The student can explain definition of redox
reactions the third concept (the change in
oxidation number concept)
1.The First Redox Concept,The Release and
Uptake of Oxygen atoms Concept
•Oxidation reaction is subtance uptakes an
oxygen molecule on the reaction.
Example :
4Na(s) + O2(g)→ 2Na2O(s)
2Cl2(g) + 3O2(g) →2Cl2O3(g)
4FeS2(s)+11O2(g)→ 2 Fe2O3(s) + 8SO2(g)
2C2H2(g) + 5O2(g) →4CO2(g) +2 H2O
•Reduction reaction is subtance releases
an oxygen molecule on the reaction.
Example :
2 HgO(s)→ 2 Hg(s)+ O2(g)
2 KClO3(s)→ 2 KCl(s)+3 O2(g)
6 CO2(g)+ 6H2O(l)→C6H12O6(s)+ 6O2(g)
2 Fe2O3(s)+ 3C(s)→4Fe(s)+3CO2(g)
2.The Second Redox Cncept,The Electrons
Transfer Concept
•Oxidation reaction is refers to the loss of
electrons.
Example :
11Na
281
12Mg
282
Na++ e
28
2+
Mg
28
+ 2e
+
Na → Na + e
+2
Mg → Mg + 2e
•Reduction reaction is refers to the gain of
electrons.
Example :
17Cl + e
287
8O
26
+ 2e
-
Cl
-
Cl2 + 2e
2Cl
O2 + 4e
2O2-
288
O228
Reaksi oksidasi selalu diikuti reaksi reduksi :
R. Oks: Na → Na+ + e x2 2Na →2Na+ +2 e
R. Red: Cl2 + 2e→2Cl- x1
R.Redoks :
-
Cl2 + 2e→2Cl
+
-
2Na + Cl2→2Na + 2Cl
2NaCl
+2
R. Oks: Mg → Mg + 2e x2 2Mg →2Mg+2 + 4e
R. Red: O2 + 4e→2O-2
x1 O2 + 4e → 2O-2
R.Redoks : 2Mg +O2 →2Mg+2 +2O-2
2MgO
The Rules to determine the okxidation numbers
1.
2.
3.
4.
5.
The oxidation numbers of
free are zero
The oxidation numbers of
mono atomic ion are equals
to its ionic charge,
The sums of oxidation
numbers of atoms in their
coumpounds are zero.
The sums oxidation numbers
is poliatomic ions are equal
to the charge of poliatomic
ions.
The oxidation numbers of
group IA element in a
compound is +1, while the
oxidation numbers of group.
IIA element in a compound is
+2
6. The oxidation numbers of
group VIIA element in a
compound is -1.
7. The oxidation numbers of
hydrogen atom in compound is
+1, exept in metal hydride its
the oxidation numbers is -1.
8. The oxidation numbers of
oxygen atom in compound is 2, exept in peroxide, its
oxidation numbers is -1. And
the oxidation numbers in
binary compound with flourine
is +2.
1.The oxidation numbers of free are zero
Example :
Na BO = 0
Al BO = 0
F2 BO =0
S8 BO =0
2. The oxidation numbers of mono atomic ion are
equals to its ionic charge,
Example :
+3
Al
BO = +3
+
Na BO = +1
-2
O
BO = -2
Cl BO = -1
-
3. The sums of oxidation numbers of atoms in
their coumpounds are zero.
5.The oxidation numbers of group IA element in a compound
is +1, while the oxidation numbers of group.
IIA element in a compound is +2
6. The oxidation numbers of group VIIA element in a
compound is -1.
Example : NaCl
Na +Cl = 0
(+1) + (-1) = 0
MgBr2
Mg +2Br = 0
(+2) + 2(-1) = 0
7.The oxidation numbers of hydrogen atom in
compound is +1, exept in metal hydride its the
oxidation numbers is -1.
8. The oxidation numbers of oxygen atom in compound
is -2, exept in peroxide, its oxidation numbers is -1.
Example :
H2O
2H + O = 0
Exept (7) : NaH Na + H = 0
2(+1) + (-2) = 0
Exept (8) :
H2O2
2H + 2O = 0
2(+1) + 2O = 0
2O = -2
(+1) + H = 0
H= -1
CaH2 Ca + 2H = 0
(+2) + 2H = 0
H= -1
Na2O2
O = -1
BaO2
4.The sums oxidation numbers is poliatomic ions are
equal to the charge of poliatomic ions.
Example :
SO4-2
S + 4O = -2
S + 4(-2) = -2
S = -2 + 8
S = +6
Exept (6) : Gol VIIA yang mengandung atom O
dalam senyawanya BO tidak -1
KClO3
K + Cl + 3O = 0
(+1)+ Cl +3(-2) = 0
Cl = +5
3.The Third Redox Concept,The Change in
Oxidation Number Concept
•Oxidation reaction is the increasing oxidation
number.
•Reduction reaction is the decreasing oxidation
number.
•Oxidant : being reduced
•Reductant : being oxidized
Example: 2Na + Cl2→2NaCl
:
0
0
R.Oksidasi
Na Reduktor
+1 -1
R.Reduksi
Cl2 Oksidator
Mg +2HCl → MgCl2 + H2
0
+1 -1
+2 -1
0
R. Oksidasi
R. Reduksi
MgCl2 Hasil
Oksidasi
H2 Hasil reduksi
Mg Reduktor HCl Oksidator
Cl2 + KOH→ KCl + KClO3 + H2O
0
+1-2+1
+1 -1 +1+5 -2
+1 -2
R. Oksidasi
R. Reduksi
KClO3 Hasil Oksidasi
KCl Hasil reduksi