Electrolysis • non-spontaneous reaction is caused by the passage of an electric current through a solution.
Download ReportTranscript Electrolysis • non-spontaneous reaction is caused by the passage of an electric current through a solution.
Slide 1
Electrolysis
• non-spontaneous reaction is caused by
the passage of an electric current through
a solution
Slide 2
Slide 3
Electrolysis
Electrolysis of Sodium chloride
(chlor-alkali process)
molten reactants => liquid sodium and
chlorine gas
aqueous reactants => caustic soda (sodium
hydroxide) and chlorine gas
Slide 4
Electrolysis
Preparation of Aluminum (Hall process)
Slide 5
Electrolytic Refining of Copper
Cu(s) + Cu+2(aq) --> Cu+2(aq) + Cu(s)
impure
pure
anode
cathode
impurities: anode mud; Ag, Au, Pb
Slide 6
Slide 7
Quantitative Aspects of Electrolysis
• 1 coulomb = 1 amp sec
• 1 mole e- = 96,500 coulombs
Slide 8
Electroplating
EXAMPLE: How many grams of chromium
can be plated from a Cr+6 solution in 45
minutes at a 25 amp current?
Slide 9
Electroplating
EXAMPLE: How many grams of chromium
can be plated from a Cr+6 solution in 45
minutes at a 25 amp current?
(45 min)
#g Cr = ------------
Slide 10
Electroplating
EXAMPLE: How many grams of chromium
can be plated from a Cr+6 solution in 45
minutes at a 25 amp current?
definition of minute
(45 min)(60 sec)
#g Cr = --------------------(1 min)
Slide 11
Electroplating
EXAMPLE: How many grams of chromium
can be plated from a Cr+6 solution in 45
minutes at a 25 amp current?
(45) (60 sec) (25 amp)
#g Cr = --------------------------(1)
Slide 12
Electroplating
EXAMPLE: How many grams of chromium
can be plated from a Cr+6 solution in 45
minutes at a 25 amp current?
definition of a coulomb
(45)(60 sec)(25 amp)(1 C)
#g Cr = ----------------------------(1)
(1 amp sec)
Slide 13
Electroplating
EXAMPLE: How many grams of chromium
can be plated from a Cr+6 solution in 45
minutes at a 25 amp current?
Faraday’s constant
(45)(25)(60)(1 C)(1 mol e-)
#g Cr = ---------------------------------(1)(1)(96,500 C)
Slide 14
Electroplating
EXAMPLE: How many grams of chromium
can be plated from a Cr+6 solution in 45
minutes at a 25 amp current?
atomic weight
(45)(60)(25)(1)(1 mol e-)(52 g Cr)
#g Cr = ------------------------------------------(1)(1)(96,500)
(6 mol e-)
Slide 15
Electroplating
EXAMPLE: How many grams of chromium
can be plated from a Cr+6 solution in 45
minutes at a 25 amp current?
(45)(60)(25)(1)(1 mol e-)(52 g Cr)
#g Cr = ------------------------------------------(1)(1)(96,500)(6 mol e-)
= 58 g Cr
Slide 16
Slide 17
Corrosion
O2(g) + 4 H+(aq) + 4 e- -----> 2 H2O(l)
Eo = 1.23 V
Rusting
Fe(s) -----> Fe+2(aq) + 2 e-
Eo = 0.44 V
O2(g) + 4 H+(aq) + 4 e- -----> 2 H2O(l)
Eo = 1.23 V
-------------------------------------------
--------------
2 Fe(s) + O2(g) + 4 H+(aq) ----->
2 H2O(l) + Fe+2(aq)
Eo = 1.67 V
Slide 18
Preventing Corrosion
painting
galvanizing
sacrificial anode
Electrolysis
• non-spontaneous reaction is caused by
the passage of an electric current through
a solution
Slide 2
Slide 3
Electrolysis
Electrolysis of Sodium chloride
(chlor-alkali process)
molten reactants => liquid sodium and
chlorine gas
aqueous reactants => caustic soda (sodium
hydroxide) and chlorine gas
Slide 4
Electrolysis
Preparation of Aluminum (Hall process)
Slide 5
Electrolytic Refining of Copper
Cu(s) + Cu+2(aq) --> Cu+2(aq) + Cu(s)
impure
pure
anode
cathode
impurities: anode mud; Ag, Au, Pb
Slide 6
Slide 7
Quantitative Aspects of Electrolysis
• 1 coulomb = 1 amp sec
• 1 mole e- = 96,500 coulombs
Slide 8
Electroplating
EXAMPLE: How many grams of chromium
can be plated from a Cr+6 solution in 45
minutes at a 25 amp current?
Slide 9
Electroplating
EXAMPLE: How many grams of chromium
can be plated from a Cr+6 solution in 45
minutes at a 25 amp current?
(45 min)
#g Cr = ------------
Slide 10
Electroplating
EXAMPLE: How many grams of chromium
can be plated from a Cr+6 solution in 45
minutes at a 25 amp current?
definition of minute
(45 min)(60 sec)
#g Cr = --------------------(1 min)
Slide 11
Electroplating
EXAMPLE: How many grams of chromium
can be plated from a Cr+6 solution in 45
minutes at a 25 amp current?
(45) (60 sec) (25 amp)
#g Cr = --------------------------(1)
Slide 12
Electroplating
EXAMPLE: How many grams of chromium
can be plated from a Cr+6 solution in 45
minutes at a 25 amp current?
definition of a coulomb
(45)(60 sec)(25 amp)(1 C)
#g Cr = ----------------------------(1)
(1 amp sec)
Slide 13
Electroplating
EXAMPLE: How many grams of chromium
can be plated from a Cr+6 solution in 45
minutes at a 25 amp current?
Faraday’s constant
(45)(25)(60)(1 C)(1 mol e-)
#g Cr = ---------------------------------(1)(1)(96,500 C)
Slide 14
Electroplating
EXAMPLE: How many grams of chromium
can be plated from a Cr+6 solution in 45
minutes at a 25 amp current?
atomic weight
(45)(60)(25)(1)(1 mol e-)(52 g Cr)
#g Cr = ------------------------------------------(1)(1)(96,500)
(6 mol e-)
Slide 15
Electroplating
EXAMPLE: How many grams of chromium
can be plated from a Cr+6 solution in 45
minutes at a 25 amp current?
(45)(60)(25)(1)(1 mol e-)(52 g Cr)
#g Cr = ------------------------------------------(1)(1)(96,500)(6 mol e-)
= 58 g Cr
Slide 16
Slide 17
Corrosion
O2(g) + 4 H+(aq) + 4 e- -----> 2 H2O(l)
Eo = 1.23 V
Rusting
Fe(s) -----> Fe+2(aq) + 2 e-
Eo = 0.44 V
O2(g) + 4 H+(aq) + 4 e- -----> 2 H2O(l)
Eo = 1.23 V
-------------------------------------------
--------------
2 Fe(s) + O2(g) + 4 H+(aq) ----->
2 H2O(l) + Fe+2(aq)
Eo = 1.67 V
Slide 18
Preventing Corrosion
painting
galvanizing
sacrificial anode