Transcript PowerPoint Presentation - Morris-Teacher-Page

V.13 Electrolysis
p. 237-246
Electrolysis
Process of supplying electrical
energy to a molten ionic
compound or a solution
containing ions so as to produce
a chemical change
Allows non-spontaneous
electrochemical rxs (E°CELL<
0) by supplying energy
Electrolytic cells do not need a
salt bridge or porous barrier to
keep reactants separated as no
spontaneous rx occurs between
the reactants
Electrodes can be inert materials,
such as Pt, C
Diagram p. 237
Na+ and Cl-
Anode: 2Cl-Cl2+2e- E=-1.36V
Cathode:2Na++2e-2Na -2.71V
Overall Rx:
2Cl-+ 2Na+ Cl2+2Na E=-4.07V
Not spontaneous; need at least
4.07V to make cell work
Ex: Aqueous NaI
Species in sol’n: Na+, I- and H2O
Find the preferred rx’s
The Preferred Rx
The one requiring the least
voltage input (closest together)
Most ex’s are neutral solutions
If acidic, substitute H+ for any
metal ions in sol’n (look @ p.240!)
“Overpotentials”
Electrolysis of aqueous solution
containing Cl- or Br-will produce
Cl2 or Br2 at the anode
p.242: 65a,b & 68 a,b