Transcript 653-ELECTROLYTIC CELL CELL PPT

ELECTROLYSIS
OF A SALT
D.C. SOURCE
(BATTERY)
SLIDE ONE
OVERVIEW
ANIMATION
Cl2
2e+
Au3+
THE ANODE IS SOLID Pt
or GRAPHITE,AND
DOES NOT REACT IN
REDOX (INERT)
+
0
-Au
- Au3+ - -
ClCl-
+
ClTHE ELECTROLYTE
SOLUTION, USUALLY
H2SO4
THIS COULD BE A
HEART CHARM
BRACELET PIECE TO
BE GOLD PLATED
THE CATHODE IS A
CHEAP PIECE OF
CONDUCTIVE
MATERIAL. THIS COULD
BE ANY CONDUCTIVE
(METAL) IN JEWELRY
TO BE GOLD PLATED.
3e-
THE SOURCE OF GOLD IS AuCl3 ( THE
THREE CHLORIDES ARE -1 EACH SO THE
Au MUST BE 3+.
ELECTROLYSIS,
SALT
SLIDE TWO
NON
SPONTANEOUS
OXIDATION
AT ANODE
D.C. SOURCE
(BATTERY)
Cl2
(DEADLY Cl2 GAS
BUBBLES OUT AT
2eANODE.)
+
Au3+
The anode (PLATINUM)
IS ELECTRON POOR
DUE THE DC SOURCE
“PUMPING” OUT
ELECTRONS. THE
CHLORIDE IONS ARE
ATTRACTED TO THE +
CHARGE OF THE
ANODE.REMEMBER
HALOGENS REACT IN
PAIRS!
+
ClCl-
- --
+
Cl-
2Cl-(aq)  Cl20 (g) + 2eOXIDATION AT ANODE
An important
characteristic of the
electrolytic cell is that
the oxidation of a LESS
active non-metal
(bottom position on
table J).
ELECTROLYSIS,
OF A SALT
D.C. SOURCE
(BATTERY)
SLIDE THREE
ELECTRON
FLOW
THE D.C. SOURCE
ACTIVLEY “PUMPS”
ELECTRONS OUT OF
THE ANODE CAUSING
IT TO BE RELATIVLEY
POSITIVE COMPARED
TO THE CATHODE.
Cl2
2e+
Au3+
+
ClCl-
+
Cl-
--
-
THE D.C. SOURCE
ACTIVLEY “PUMPS”
ELECTRONS ITO THE
CATHODE, CAUSING IT
TO BE NEGATIVE
RELATIVE TO THE
ANODE. THIS HIGH
DENSITY OF
ELECTRONS AT THE
CATHODE WILL
“FORCE” A REDUCTION
TO OCCUR.
ELECTROLYSIS
SALT
D.C. SOURCE
(BATTERY)
SLIDE FOUR
NON
SPONTANEOUS
REDUCTION AT
CATHODE
THE CHLORIDE IONS
CONTINUE TO
MIGRATE TO THE
ANODE AS THE GOLD
MIGRATES TO THE
ANODE.
Au3+
THE SOLID GOLD
THAT WAS
PRODUCED
DURING
REDUCTION
ELECTROPLATE
S THE CATHODE
AS SOLID GOLD
Cl2
2e+
Au
+
-
Au3+
Au0
Cl- Au3+
Cl-
+
Cl+ 3e- 
-
3e-
Au0
REDUCTION AT CATHODE
THE GOLD(III)
CATIONS MIGRATE TO
THE ELECTRON RICH,
NEGATIVELY
CHARGED CATHODE
WHERE THEY WILL BE
FORCED TO BE
REDUCED TO Au0
SOLID.
BALANCING THE HALF REACTIONS
2Cl-(aq)  Cl20 (g) + 2eAu3+
+ 3e- 
Au0
3( 2Cl-(aq) Cl20 (g) + 2e- )
2(Au3+
+ 3e- Au0 )
6Cl-(aq)  3Cl20 (g)+ 6e2Au3+
+ 6e- 2Au0
2Au3+ (aq) + 6Cl-(aq)  3Cl20 (g) + 2Au3+(aq)
THE
ELECTRONS
MUST CANCEL,
THE LCD IS 6,
FACTORS ARE 3
AND 2.
REVIEW OF
ELECTROCHEMICAL
CELL TYPES
VOLTAIC CELL
ELECTROLYTIC
CELL
SPONTANEITY
SPONTANEOUS
NOT
SPONTANEOUS
METAL OXIDIZED
TOP OF TABLE “J”
BOTTOM OF “J”
CATHODE
POSITIVE:SPONTANEOUS
REDUCTION CONSUMES
ELECTRONS.
NEGATIVE: DC SOURCE
(BATTERY) FORCES
ELECTRONS HERE.
POSITIVE: D.C. SOURCE
PULLS ELECTRONS OUT.
OXIDATION IN BOTH CELLS
NEGATIVE: SPONTANEOUS
OXIDATION SUPPLIES
ELECTRONS HERE.
ENERGY
EXOTHERMIC
ENDOTHERMIC
ELECTRON
FLOW
ELECTRON
GRADIENT
FROM ANODE
TO CATHODE
HIGH TO LOW
ENERGY
FROM ANODE
TO CATHODE
LOW TO HIGH
ENERGY
REDUCTION IN BOTH CELLS
ANODE