3.2.16 (HL)—Electroplating

The object being coated is the cathode, where coating-metal ions are reduced to metal. Use an electrolyte containing those ions; a coating-metal anode can replenish them.

$M^(n+) + ne− → M(s) at the object cathode$

Trace metal atoms through the circuit: M atoms may oxidize at a soluble anode to maintain Mⁿ⁺, while Mⁿ⁺ gains electrons and deposits on the object. Reversing the object to the anode would remove metal rather than coat it.

Representative question

[Maximum number: 3]

Describe how electrolysis can be used to electroplate a bracelet with a layer of silver metal. Include the choice of electrodes and electrolyte needed in your description.

bracelet/object to be electroplated is the cathode/negative electrode;\nsilver anode/positive electrode;\nelectrolyte: liquid $\mathrm{Na}[\mathrm{Ag}(\mathrm{CN})_{2}]$ / sodium dicyanoargentate / $\left[\mathrm{Ag}(\mathrm{CN})_{2}\right]^{-}$ / solution of an appropriate silver salt / $\mathrm{AgNO}_{3}$ / silver nitrate;

Retrieve the route: assign oxidation states, balance half-equations, predict displacement, label cells, trace electrons and ions, follow organic redox pathways, calculate potentials and choose electrolysis products.

Check electron loss/gain, anode/cathode versus polarity, spontaneous sign, salt-bridge direction, ions present, organic functional-group direction and object-cathode placement.

3.2.16 (HL)—Electroplating

Electroplating with Electrolysis

Designing an Electroplating Cell

Assessment in practice

Electron Transfer Reactions Summary

Question 1