Question 4 Answer

(a) When current passed through the electrolyte the pure chromium decompose.

Anode:

Cr (s) – 3e-   → Cr 3+ (aq)

Cathode:

 Cr 3+ (aq) + 3e- → Cr(s)

(b) To prevent corrosion

To make an object look more attractive

(shiny, silver looking finish)

Anode:  SO42-, OH-

OH- discharged lower in the electrochemical series.

Cathode: Cu2+, H+

Cu2+ discharged lower in the electrochemical series.

Anode: Oxidation occur

4OH – (aq) – 4e- → 2H2O + O2

Cathode: Reduction occur

Cu2+ (aq) + 4e- → 2 Cu(s)

Q = It

= 5A x 2 x 3600s
= 360,000C

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