Question 1

What is the difference between the anode and cathode in electrolysis?

Accepted Answer

The anode is connected to the positive terminal of the external power source and is the site of oxidation. The cathode is connected to the negative terminal and is the site of reduction. These names are based on the reactions, not on a universal red or black colour code.

Question 2

Why is hydrogen gas produced at the cathode during water electrolysis?

Accepted Answer

At the cathode, reduction occurs and hydrogen ions from water accept electrons to form hydrogen gas. With inert electrodes, hydrogen is released at the cathode while oxygen is released at the anode.

Question 3

Why do hydrogen and oxygen form a 2:1 volume ratio?

Accepted Answer

The half-reactions produce two volumes of hydrogen for every one volume of oxygen. Therefore, when gases are compared at the same temperature and pressure, the H2 to O2 volume ratio is 2:1.

Question 4

What happens when concentrated aqueous CuCl2 is electrolysed with inert Pt electrodes?

Accepted Answer

Cu2+ ions migrate toward the cathode and are reduced to copper metal, which forms a deposit on the cathode. At the anode, chloride ions are oxidized to chlorine gas. In dilute CuCl2 solution, oxidation of water to oxygen can compete with chlorine formation at the anode.

Question 5

How does an active copper anode change CuCl2 electrolysis?

Accepted Answer

The copper anode itself is oxidized to Cu2+ ions, so the anode loses mass. Those copper ions migrate through the solution and are reduced at the cathode, where copper is deposited.

Electrolysis & Faraday's Laws — Watch Charge Become Mass

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