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Direct electrolysis of seawater follows known processes, forming an electrolysis cell in which the seawater acts as the electrolyte to allow for the reaction at the anode, 2 Cl − (aq) → Cl 2 (g) + 2e − and the reaction at the cathode, 2 H 2 O(l) + 2 e − → H 2 (g) + 2OH − (aq).
Electrolysis in pure water consumes/reduces H + cations at the cathode and consumes/oxidizes hydroxide (OH −) anions at the anode. This can be verified by adding a pH indicator to the water: Water near the cathode is basic while water near the anode is acidic.
Electrolytic cells are often used to decompose chemical compounds, in a process called electrolysis—with electro meaning electricity [5] and the Greek word lysis means to break up. Important examples of electrolysis are the decomposition of water into hydrogen and oxygen , and bauxite into aluminum and other chemicals.
The terms anode and cathode are not defined by the voltage polarity of electrodes, but are usually defined by the direction of current through the electrode. An anode usually is the electrode of a device through which conventional current (positive charge) flows into the device from an external circuit, while a cathode usually is the electrode through which conventional current flows out of ...
Cathode: 4H 2 O + 4e(-) → 4OH(-) + 2H 2 (gas) In anodic deposition, the material being deposited will have salts of an acid as the charge bearing group. These negatively charged anions react with the positively charged hydrogen ions (protons) which are being produced at the anode by the electrolysis of water to reform the original acid.
The net cell reaction yields hydrogen and oxygen gases. The reactions for one mole of water are shown below, with oxidation of oxide ions occurring at the anode and reduction of water occurring at the cathode. Anode: 2 O 2− → O 2 + 4 e −. Cathode: H 2 O + 2 e − → H 2 + O 2−. Net Reaction: 2 H 2 O → 2 H 2 + O 2
The reaction at anode (A) is: 2 Cl − → Cl 2 + 2 e −. The chlorine gas that results vents at the top of the outside cells where it is collected as a byproduct of the process. The reaction at the mercury cathode in the outer cells is Na + + e − → Na (amalgam) The sodium metal formed by this reaction dissolves in the mercury to form an ...
Mixtures of both gases at the electrodes result. At the cathode, oxygen can be catalytically reacted with hydrogen on the platinum surface of the cathodic catalyst. At the anode, hydrogen and oxygen do not react at the iridium oxide catalyst. [15] Thus, safety hazards due to explosive anodic mixtures hydrogen in oxygen can result.