Question

Acidified water is electrolysed by using carbon electrodes. What is produced at the negative carbon electrode?

Answer 1

Electrolysis of water is the process in which we use electricity to decompose water into oxygen and hydrogen gas. Hydrogen gas released in this way is very useful and can be used as hydrogen fuel, or remixed with the oxygen to create oxyhydrogen gas. This is used in welding and other industrial applications.

Complete answer:
When we add any salt to the water, the ions in the salt (which are highly polar) help to pull the water molecules apart into ions. We know that each part of the water molecule has a charge. The $O{H^ - }$ ion is negative and the ${H^ + }$ ion is positive. This solution in water will form an electrolyte, allowing current to flow when a voltage is applied to it. The ${H^ + }$ ions, called the cations will move toward the cathode which is negatively charged electrode, and the $O{H^ - }$ ions, called the anions will move towards the anode which is positively charged electrode. Bubbles of oxygen gas will form at the anode, and bubbles of hydrogen gas will form at the cathode. This can be easily observed and we can notice that the volume of the hydrogen gas will be twice that of oxygen gas.
Therefore we can say that when we use an inert electrode we obtain hydrogen gas at the negatively charged electrode.

Note:
Carbon electrodes will allow more negative potentials than platinum or gold electrodes. It will also provide a good anodic potential window. Water hydrolysis serves a lot of industrial applications.
Real water electrolysers require higher voltages for the reaction to proceed than the theoretical calculated values. This part that exceeds 1.23 V is called over potential or overvoltage, and represents any kind of loss and non-ideality in the electrochemical process.