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The Electrolytic Cell. The Electrolytic Cell. In the electrolytic cell , a nonspontaneous redox reaction is forced to occur by the use of a source of electricity. In the electrolytic cell , electrons are FORCED to flow from the positive electrode to the negative electrode! - PowerPoint PPT Presentation
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The Electrolytic Cell
• In the electrolytic cell, a nonspontaneous redox reaction is forced to occur by the use of a source of electricity.
• In the electrolytic cell, electrons are FORCED to flow from the positive electrode to the negative electrode!
• In the electrolytic cell, the cathode has a negative charge and the anode has a positive charge!
The Electrolytic Cell
• Electrolytic cells are used to purify highly reactive elements from their compounds!
• Na0 (sodium) never exists pure in nature!• Pure sodium can be extracted from NaCl by
using an electrolytic cell.
The Electrolytic Cell
Ex.1)
• Electrons always flow out of the negative pole of an electric source such as a battery.
• Electrons always flow towards the cathode.
battery+ -
NaCl(l)
e-
cathodeanode
Put a + on the positive
electrode and a - on the negative
electrode.
+ -
The Electrolytic Cell
Ex.1)
Write the reduction half reaction: ______________________
Write the oxidation half reaction: ______________________
battery+ -
NaCl(l)
e-
cathodeanode
Cl1- → Cl20 + 2 e-2
Na1+ → Na0+ 1 e-2 2 2
+1 -1
Na Cl2
0 0
The Electrolytic Cell
Ex.1)
_______________________________[write the balanced redox reaction]
battery+ -
NaCl(l)
e-
cathodeanode
+1 -1
Na Cl2
0 0
Na1+ Na0Cl1- → Cl2022 2+ +
The Electrolytic Cell
Ex.1)
a) The electrode on the left is the ____ode and the
electrode on the right is the ____ode.
battery+ -
NaCl(l)
e-
+1 -1
Na Cl2
0 0
an
cath
The Electrolytic Cell
Ex.1)
b) The positive electrode is on the __________ and the
negative electrode is on the __________.
battery+ -
NaCl(l)
e-
+1 -1
Na Cl2
0 0
leftright
The Electrolytic Cell
Ex.1)
c) Write the half reaction that occurs at the electrode on
the left.
battery+ -
NaCl(l)
e-
+1 -1
Na Cl2
0 0
_________________________________________Cl1- → Cl20 + 2 e-2
The Electrolytic Cell
Ex.1)
d) Write the half reaction that occurs at the electrode on
the right.
battery+ -
NaCl(l)
e-
+1 -1
Na Cl2
0 0
_________________________________________Na1+ → Na0+ 1 e-
The Electrolytic Cell
Ex.2)
• Electrons always flow out of the negative pole of an electric source such as a battery.
• Electrons always flow towards the cathode.
battery +-
KBr(l)
e-
cathode anode
Put a + on the positive
electrode and a - on the negative
electrode.
+-
The Electrolytic Cell
Ex.2)
Write the reduction half reaction: ______________________
Write the oxidation half reaction: ______________________
battery
Br1- → Br20 + 2 e-2
K1+ → K0+ 1 e-2 2 2
+1 -1
K Br2
0 0
cathode anode
e-
KBr(l)
- +
The Electrolytic Cell
Ex.2)
_______________________________[write the balanced redox reaction]
battery
+1 -1
K Br2
0 0
K1+ K0Br1- → Br2022 2+ +
e-
cathode anode
KBr(l)
- +
The Electrolytic Cell
Ex.2)
a) The electrode on the left is the ____ode and the
electrode on the right is the ____ode.
battery
+1 -1
K Br2
0 0
- +
KBr(l)
cath
an
The Electrolytic Cell
Ex.2)
b) The positive electrode is on the __________ and the
negative electrode is on the __________.
battery
+1 -1
K Br2
0 0
e-
KBr(l)
- +
right
left
The Electrolytic Cell
Ex.2)
c) Write the half reaction that occurs at the electrode on
the left.
battery
+1 -1
K Br2
0 0
e-
- +
KBr(l)
_________________________________________K1+ → K0+ 1 e-
The Electrolytic Cell
Ex.2)
d) Write the half reaction that occurs at the electrode on
the right.
battery
+1 -1
K Br2
0 0
+e-
-
KBr(l)
_________________________________________Br1- → Br20 + 2 e-2
The Electrolytic Cell
Ex.3)
• Electrons always flow out of the negative pole of an electric source such as a battery.
• Electrons always flow towards the cathode.
battery +-
H2O(l)
e-
cathode anode
Put a + on the positive
electrode and a - on the negative
electrode.
+-
The Electrolytic Cell
Ex.3)
_______________________________[write the balanced redox reaction]
battery
+1 -2
H2 O2
0 0
H2O H20→ O2
02 2 +
e-
cathode anode- +
H2O(l)
The Electrolytic Cell
Ex.3)
a) The electrode on the left is the ____ode and the
electrode on the right is the ____ode.
battery
+1 -2
0 0
- +
H2O(l)
H2 O2
cath
an
The Electrolytic Cell
Ex.3)
b) The positive electrode is on the __________ and the
negative electrode is on the __________.
battery
+1 -2
0 0
e-
- +
H2O(l)
H2 O2
right
left
The Electrolytic Cell
Ex.3)
c) What substance is produced at the electrode on
the left? ____________________
battery
+1 -2
0 0
e-
- +
H2O(l)
H2 O2
Hydrogen gas
The Electrolytic Cell
Ex.3)
d) What substance is produced at the electrode on
the right? ____________________
battery
+1 -2
0 0
e-
- +
H2O(l)
H2 O2
Oxygen gas
The Electrolytic Cell
Ex.3)
e) Why must a small amount of electrolyte (such as anacid) be added to the water in order for the
electrolytic decomposition to work?
___________________________________________________________________
battery
+1 -2
0 0
e-
- +
H2O(l)
H2 O2
because pure water does
not conduct electricity, so an electrolyte is added.
The Electrolytic Cell
Ex. (4) Which half-reaction correctly represents the reduction of a potassium ion?
(1) K+ + e- → K (3) K+ → K + e-
(2) K + e- → K+ (4) K → K+ + e-
Ex. (5) Given the equation:
2 Al + 3 Cu2+ → 2 Al3+ + 3 Cu
The oxidation half-reaction is
(1) Al → Al3+ + 3e- (3) Al + 3e- → Al3+
(2) Cu2+ + 2e- → Cu (4) Cu2+ → Cu + 2e-
The Electrolytic Cell
Ex. (6) During the electrolysis of molten cesium chloride (CsCl), pure cesium is produced at the
(1) positively charged cathode and pure chloride gas is produced at the negatively charged anode
(2) negatively charged cathode and pure chloride gas is produced at the positively charged anode
(3) positively charged anode and pure chloride gas is produced at the negatively charged cathode
(4) negatively charged anode and pure chloride gas is produced at the positively charged cathode
The Electrolytic CellEx. (7) Given the voltaic cell:
Pb(s) + Cu2+(aq) → Pb2+
(aq) + Cu(s)
The electrons will flow from (1) the Pb(s) electrode to the Cu(s) electrode (2) the Cu(s) electrode to the Pb(s) electrode (3) the Pb2+
(aq) electrode to the Cu(s) electrode (4) the Cu2+
(aq) electrode to the Pb(s) electrode
Ex. (8) What is conserved during all chemical reactions? (1) mass, only (3) both mass and charge (2) charge, only (4) neither mass nor charge
+ Battery -e-
Molten NaCl(ℓ)
e-
Na+
Na+
Na+
Na+
Na+
Cl-
Cl-
Cl-
Cl-
Cl-
Cl20
Na0
CathodeAnode
-+
2 NaCl 2 Na + Cl2
Reduction: 2 Na+1 + 2e- 2 Na0
Oxidation: 2 Cl-1 Cl20 + 2 e-
Na0
The Electrolytic Cell
Na0
Na0
Na0
Na0
Na0
Na0
Na0
Na0 Na0
Na0Na0
Na0
Na0
Molten Na(ℓ)
Na0
Na0
Na0
Na0
Na0
+ Battery -e-
aqueous CuBr2(aq)
e-
Cu+2
Cu+2
Cu+2
Br-
Br-
Br-
Br-
H2O
Br20
Cu0
CathodeAnode
-+
CuBr2 Cu + Br2
Reduction: Cu+2 + 2e- Cu0
Oxidation: 2 Br-1 Br20 + 2 e-
Br-
Br-
H2O
H2O
H2O
H2OH2O
The Electrolytic Cell
- Battery +e-
H2O(ℓ)
e-
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H20
O20
AnodeCathode
+-
2 H2O 2 H2 + O2
Reduction: 4 H+1 + 4e- 2 H20
Oxidation: 2 O-2 O20 + 4 e-
H20
O-2
O-2
H+1
H+1H+1
H+1
The Electrolytic Cell