Chemistry
Give balanced equations for the electrode reactions involved in the following conversions at the respective electrodes:
- Aluminium oxide → Oxygen gas ← Copper [II] Sulphate
- Copper metal → Copper ions → Copper metal
- Lead [II] chloride → Chlorine gas ← Hydrochloric acid
- Hydroxyl ions ← Acidified water → Oxygen gas
- Potassium bromide → Bromine gas ← Lead bromide
Electrolysis
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Answer
- Aluminium oxide → Oxygen gas ← Copper [II] Sulphate
Electrolysis of molten Al2O3:
Al2O3 ⇌ 2Al3+ + 3O2-
Reaction at anode:
3O2- - 6e-⟶ 3[O]
3[O] + 3[O] ⟶ 3O2 [product O2 gas]
Electrolysis of copper (II) sulphate:
CuSO4 ⇌ Cu2+ + SO42- [ions present]
H2O ⇌ H1+ + OH1-
Reaction at anode:
OH1- - 1e-⟶ OH x 4
4OH ⟶ 2H2O + O2 [product oxygen gas] - Copper metal → Copper ions → Copper metal
Reaction at anode:
Cu – 2e- ⟶ Cu2+
Reaction at cathode:
Cu2+ + 2e- ⟶ Cu - Lead [II] chloride → Chlorine gas ← Hydrochloric acid
Electrolysis of molten PbCl2:
PbCl2 ⇌ Pb2+ + 2Cl-
Reaction at anode:
2Cl- – 2e- ⟶ 2[Cl]
Cl + Cl ⟶ Cl2
Electrolysis of hydrochloric acid:
HCl ⇌ H+ + Cl-
Reaction at anode:
2Cl- – 2e- ⟶ 2[Cl]
Cl + Cl ⟶ Cl2 - Hydroxyl ions ← Acidified water → Oxygen gas
Electrolysis of acidified water
H2SO4 ⇌ 2H1+ + SO42-
H2O ⇌ H1+ + OH1-
Reaction at anode:
OH1- - 1e- ⟶ OH x 4
4OH ⟶ 2H2O + O2 [product oxygen gas] - Potassium bromide → Bromine gas ← Lead bromide
Electrolysis of molten KBr:
KBr ⇌ K1+ + Br1-
Reaction at anode:
Br- – 1e- ⟶ Br
Br + Br ⟶ Br2
Electrolysis of molten PbBr2:
PbBr2 ⇌ Pb2+ + 2Br-
Reaction at anode:
Br- – 1e- ⟶ Br
Br + Br ⟶ Br2
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Related Questions
Complete the table given below:
Nature of Anode Nature of Cathode Ions present in electrolyte Ion/s discharged at Cathode / Anode 1. Electroplating an iron rod with silver 2. Electroplating a copper sheet with nickel 3. Electrorefining of silver 4. Extraction of potassium from KCl 5. Extraction of aluminium from Al2O3 Select the correct word from the words in bracket to complete the sentence:
The electrode at which anions donate excess electrons and are oxidized to neutral atoms is the …………… [anode/cathode]
On electrolysis, Ag1+ and H1+ ions migrate to the …………… [cathode/anode] and …………… [Ag1+/H1+] are discharged.
Electrolysis is a / an …………… [oxidation/reduction/redox] reaction in which reduction reaction takes place at the …………… [cathode/anode].
According to Arrhenius's theory the amount of electricity conducted by the electrolyte depends on the …………… [nature/concentration] of the ions in solution.
Salts ionize in aq. soln. on passage of electric current to give …………… [negative/positive] ions other than H+ ions.
Select the correct answer from the list in bracket:
- The cation discharged at the cathode most readily.
[Fe2+, Cu2+, Pb2+, H1+] - The anion discharged at the anode with most difficulty.
[SO42-, Br1-, NO31-,OH1-] - The metallic electrode which does not take part in an electrolytic reaction.
[Cu, Ag, Fe, Ni] - The ion/s which is/are discharged during electrolysis of aq. CuSO4 using Cu electrode.
[Cu2+, SO42-, H1+, OH1-] - A covalent compound which in aqueous state conducts electricity.
[CCl4, CS2, NH3, C2H4]
- The cation discharged at the cathode most readily.
Give reason for the following :
Electrolysis of molten lead bromide is considered a redox reaction.