[lregnidemvopthyjbfdzckdej]

I read everything on the Internet about electolysis but I cannot understand a lot of things. How produced red rust (Fe2O3) on one of the electrodes? Could someone please write step by step what's happening during electolysis started from I put salt in a bowl of pure water, NaCl become Na+ and Cl- due to bipolar H2O, then I deep two iron plate/rod into this "salted" water and connect a 9V battery to these...

[Borek]

Do you know what redox reaction is?

[lregnidemvopthyjbfdzckdej]

Do you know what redox reaction is?

Yes, I know but I'm interesting in this more deeply. For example: why need less energy (voltage) to break a H+ from H2O if there is dissolved NaCl (Na+ and Cl-) in it? And Na+ will cover the cathode? Or just the H+ can get e- from it? And so one...

[Borek]

For example: why need less energy (voltage) to break a H+ from H2O if there is dissolved NaCl (Na+ and Cl-) in it?

This is more physics than chemistry. Presence of dissolved NaCl doesn't change the reactions taking place on the electrodes (well, to some extent it does, but let's ignore it for now as you don't understand basics yes). During electrolysis you typically want rather high currents, as it is charge that counts when talking about amount of products (see Faraday's electrolysis laws). What NaCl does is it changes the resistivity of the solution. The higher the resistance, the higher the voltage needed for the current to flow, so we want the resistance to be as low as possible, and we can lower the resistance by adding ions (charge carriers).