Everything Science Grade 12

4.6 CHAPTER 4. ELECTROCHEMICAL REACTIONS

+ –

+ –

positive anode negative cathode

impure copper electrode pure copper electrode

Cu2+

Figure 4.6: A simplifieddiagram to illustrate what happens during the electrowinning
of copper

The production of chlorine ESCCC

Electrolysis can also beused to produce chlorine gas from seawater (brine, NaCl). This
is sometimes referred toas the ’Chlor-alkali’ process. The reactions that take place are
as follows:

At the anode the reaction is:

2 Cl−→ Cl 2 (g) + 2e−

whereas at the cathode, the following happens:

2 Na++ 2H 2 O + 2e−→ 2 Na++ 2OH−+ H 2

The overall reaction is:

2 Na++ 2H 2 O + 2Cl−→ 2 Na++ 2OH−+ H 2 + Cl 2