I wonder about the figures in this exercise.
5×106 molecules/s make a current badly difficult to measure. Electrical engineers meditate for long the precautions they need before trying such an experiment, and among the very first condition are to superdry all parts and circuits, build guard rings everywhere, add varnish one the conductor tracks. Now the exercise tells "electrolyte". My intuition shouts "unrealistic", by 4 to 6 magnitudes.
And then, under what conditions shall we isolate one molecule? In what kind of cell shall the molecule arrive 5 million times per second at an electrode? Or is there some overclever trick that I missed in the setup?
Take a proton: mobility 3.62×10−3cm2V−1s−1. 5V need a cell 0.6µm long for 0.2µs transit time, neglecting the velocity saturation. Is this microelectronics?