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electrolysis - Coggle Diagram
electrolysis
components
of an electrolytic cell
power source
(battery or mains): positive & negative terminal
connecting
wires
electrodes
cathode:
connected to negative terminal of power source
anode:
connected to negative terminal of power source
active
(reactive) (
all
other metals)
anode ionized (oxidised) instead of discharge of anions: anode "dissolves"
applications
purification of copper: impure copper is anode, cathode is pure copper
electroplating: anode is pure copper, cathode is object
inert
(graphite/platinum)
no effect on discharge of ions
electrolyte
molten
(binary ionic compounds)
cations
discharged by
reduction
(accept electrons) at cathode (Red Cat)
anions
discharged by
oxidation
(lose electrons) at anode (An Ox)
aqueous
(binary ionic or otherwise, acids)
auto-ionization of water:
selective (preferential) discharge
of ions
cations
below
H+: discharged in preference to H+, because they are reduced more easily than H+
cations
above
H+: H+ discharged in preference because they are reduced more easily than these cations
anions like F-, SO42- and NO3-:
OH- discharged in preference
- irrespective of concentration
Cl-, Br-, I-:
dilute
solution - OH- discharged in preference,
concentrated
solution, Cl-, Br- & I- discharged in preference.
observations
and
products
of electrolysis
cathode:
usually hydrogen gas (as effervescence) or a metal (coated as a solid in aqueous electrolytes) or as a liquid in a molten electrolyte
anode:
usually oxygen or halogen (as effervescence) for inert anode, or ionization of anode for active anode
electrolyte:
discharge of
coloured transition metal ions
results in fading of the colour
hydrogen ions
will cause pH to increase: [H+] < [OH-]
hydroxide ions
will cause pH to decrease:
[H+] > [OH-]