Why is twice as much hydrogen produced than chlorine in the electrolysis of brine? I have seen a great many number of diagrams which show the electrolysis of brine in a diaphragm cell, but show twice the volume of hydrogen produced. For example:



On the other hand, other diagrams show that the same volume of hydrogen and chlorine is produced. For example:



So who's right and why?
It appears, as the others have said that the same number of moles of gas of chlorine and hydrogen is produced.

Then why are there different levels of solution?

Since the solution is taken out in the cathode chamber, the level of solution present is lower than the anode chamber where sodium chloride solution is being added in.