The Membrane Cell

:: most modern
:: no environmental risks - no mercury used
:: most energy efficient - cost effective
:: produces a purer product

How does the Membrane Cell work?
You must relate each point below to the diagram above.

1. A saturated solution of brine flows into the anode (positive) compartment.
NaCl(s) → Na+(aq) + Cl-(aq)

2. The Cl- ions react by REDOX:
2Cl- → Cl2 + 2e- (O1/2R)

3. The Cl2 now exits the cell.

4. The Na+ ions that are now left behind, move through the “one way” membrane.

5. H2O enters the cathode (negative) compartment. The following REDOX reaction occurs:
2H2O + 2e- → H2 + 2OH- (R1/2R)

6. The H2 exits. OH- remains behind.

7. The Na+ combines with the OH- to form NaOH.

8. The NaOH exits.

Fresh brine flows continuously into the cell as it is being used up. The membrane (polymer) has negative charges built into it to help attract the Na+ through to the cathode side, to the awaiting OH- ions.

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