Question

A metal article is to be electroplated with silver. The electrolyte selected is sodium argentocyanide.
(i) What kind of salt is sodium argentocyanide.
(ii) Why is it preferred to silver nitrate as an electrolyte?
(iii) State one condition to ensure that the deposit is smooth, firm and long lasting.
(iv) Write the reaction taking place at the cathode.
(v) Write the reaction taking place at the anode.

August 8, 2024

Answer

(i) It is a Complex Salt.

(ii) Migration of Ag¹⁺ ions from above complex salt soln. is slow compared to that from silver nitrate. Hence, an even deposition of metal silver is obtained on the article. Therefore, the electrolyte sodium argentocyanide soln. is preferred over silver nitrate solution.

(iii) A low current for a longer time should be used to ensure that the deposit is smooth, firm and long lasting.

(iv) Ag¹⁺ + 1e^– ⟶ Ag [deposited]

(v) Ag – 1e^– ⟶ Ag¹⁺ [Anode diminishes in mass]

💡 Some Related Questions

The metal oxide which can react with acid as well as alkali is :
1. Silver oxide
2. Copper [II] oxide
3. Aluminium oxide
4. Calcium oxide

Give reason for the following :
In the electrolysis of acidified water, dilute sulphuric acid is preferred to dilute nitric acid.

Give reason for the following :
During electrolytic dissociation of sodium chloride, the sodium ions are discharged at the cathode.

Give reason for the following : The blue colour of aq. copper sulphate does not change when it is electrolysed using copper electrodes.

Give reason for the following : Lead bromide undergoes electrolytic dissociation in the molten state but is a non-electrolyte in the solid state.

Give reason for the following : Electrolysis of molten lead bromide is considered a redox reaction.

Select the correct answer from the list in bracket:
1. The cation discharged at the cathode most readily. [Fe2+, Cu2+, Pb2+, H1+]
2. The anion discharged at the anode with most difficulty. [SO42-, Br1-, NO31-,OH1-]
3. The metallic electrode which does not take part in an electrolytic reaction. [Cu, Ag, Fe, Ni]
4. The ion/s which is/are discharged during electrolysis of aq. CuSO4 using Cu electrode. [Cu2+, SO42-, H1+, OH1-]
5. A covalent compound which in aqueous state conducts electricity. [CCl4, CS2, NH3, C2H4]

Give balanced equations for the electrode reactions involved in the following conversions at the respective electrodes:
1. Aluminium oxide → Oxygen gas ← Copper [II] Sulphate
2. Copper metal → Copper ions → Copper metal
3. Lead [II] chloride → Chlorine gas ← Hydrochloric acid
4. Hydroxyl ions ← Acidified water → Oxygen gas
5. Potassium bromide → Bromine gas ← Lead bromide

Select the correct word from the words in brackets to complete the sentence:
1. The electrode at which anions donate excess electrons and are oxidized to neutral atoms is the …………… [anode/cathode]
2. On electrolysis, Ag1+ and H1+ ions migrate to the …………… [cathode/anode] and …………… [Ag1+/H1+] are discharged.
3. Electrolysis is a / an …………… [oxidation/reduction/redox] reaction in which reduction reaction takes place at the …………… [cathode/anode].
4. According to Arrhenius’s theory the amount of electricity conducted by the electrolyte depends on the …………… [nature/concentration] of the ions in solution.
5. Salts ionize in aq. soln. on passage of electric current to give …………… [negative/positive] ions other than H+ ions.

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