(a) If a steel spoon were to be plated with silver, state what would be suitable for use as the; (i) anode. (ii) cathode; (iii) electrolyte (b)(i) Write an ...
Question 1 Report
(a) If a steel spoon were to be plated with silver, state what would be suitable for use as the;
(i) anode. (ii) cathode; (iii) electrolyte
(b)(i) Write an equation for one of the reactions involved in the purification of bauxite.
(ii) Give the reason why the carbon anodes are changed at intervals during the electrolysis of pure alumina solution in molten cryolite.
Answer Details
(a) To electroplate a steel spoon with silver:
- (i) Anode: a bar (plate) of pure silver metal (which dissolves to replenish the silver ions).
- (ii) Cathode: the steel spoon itself (the article to be plated).
- (iii) Electrolyte: a solution of a soluble silver salt, e.g. silver trioxonitrate(V) solution, \(AgNO_3\) (a solution of potassium argentocyanide is used industrially).
(b)(i) An equation for one reaction in the purification of bauxite (dissolving the amphoteric aluminium oxide in hot sodium hydroxide, leaving impurities behind):
\[Al_2O_3 + 2NaOH \rightarrow 2NaAlO_2 + H_2O\]
(ii) The carbon anodes must be changed (replaced) at intervals because the oxygen liberated at the anode reacts with the hot carbon to form carbon(IV) oxide (and carbon(II) oxide), so the carbon anodes gradually burn away (are oxidized) and become too small to use.
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