SC10 - Electrolytic processes

what is electrolysis?

to break down substances with the use of electricity

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(decompose electrolytes with electrical energy, from a direct current supply)

what is an electrolyte?

an ionic substance with freely moving ions + can conduct electricity

…………. charged cations go to the …………. charged cathode

cation +

cathode -

…………… charged anions go to the …………… charged anode

anion-

anode+

OIL RIG?

oxidation loss

reduction gain

(of electrons)

oxidation is gain of

reduction is loss of

oxygen

where does oxidation occur in electrolysis

ANODE - ION LOOSES ELECTRON

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(element → element + electrons)

(2O- → O2 + 2e-)

where does reduction occur in electrolysis

CATHODE + ION GAINS ELECTRON

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(element + electrons → element)

(2H+ + 2e- → H2)

where is the metal produced during electrolysis?

at the cathode

where is the non-metal produced during electrolysis?

at the anode

METAL IS

REDUCED

NON-METAL IS

OXIDISED

AT THE CATHODE

element ↑ reactive than H2 = H2 produced

element ↓ reactive than H2 = that element produced

AT THE ANODE

if halides present ( F- CL- Br- I-) = halide discharged

if not present = OXYGEN DISCHARGED

copper chloride solution

IONS: Cu2+ CL- OH- H2

cathode: Cu2+ and H2

copper less reactive than hydrogen so copper is formed at cathode (2Cu+ + 2e- → Cu) REDUCED

anode: CL- and OH-

halide is present so halide is formed (2CL- → 2e + CL2) OXIDISED

molten lead bromide

IONS: Pb2+ Br- OH- H2

cathode: Pb2+ and H2

lead is less reactive than H2 so lead is formed (Pb2+ 2e- → Pb) REDUCED

anode: Br- OH-

halide is present, so halide is formed (2Br- → Br2 +2e-) OXIDISED

(core practical) ELECTROLYSIS OF COPPER SULFATE SOLUTION with __**inert**__ electrodes

inert e.g. graphite

(core practical) ELECTROLYSIS OF COPPER SULFATE SOLUTION with __**copper**__ electrodes

(used in copper refining to get pure copper)

cathode: copper is produced

anode: copper is more easily oxidised than sulfate/hydroxide ions so sulfate

ANODE DONATES COPPER INTO SOLUTION AND PICKED UP AT CATHODE TO TURN BACK INTO COPPER METAL

why is copper produced at the anode during electrolysis of copper sulfate with COPPER electrodes?

as the copper is more easily oxidised than the sulfate or hydroxide ions