Experimenting with Electrolysis: Mystery of Yellow Water

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Discussion Overview

The discussion revolves around an experiment involving electrolysis of water using a 9v battery, steel electrodes, and NaCl. Participants explore the unexpected yellow coloration of the water and the gas production at the electrodes, questioning the chemical processes involved and the materials used.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant describes their setup and observes that only the anode produces gas while the water turns yellow, questioning if the yellow color could be chlorine (Cl2).
  • Another participant asserts that during electrolysis, chloride ions (Cl-) are oxidized to chlorine gas at the anode, while hydrogen gas is produced at the cathode, leading to a basic solution around the cathode.
  • A different participant suggests that chlorine is not very soluble in water and implies that the yellow color may be due to the dissolution of electrode material instead.
  • A later reply confirms the dissolution of electrode material and mentions switching to carbon electrodes, which resolved the issue and allowed for proper gas evolution.
  • The participant who changed electrodes speculates that the yellow color could be due to the formation of iron (III) chloride from the reaction of chlorine with iron.

Areas of Agreement / Disagreement

Participants express differing views on the cause of the yellow coloration and the reactions occurring at the electrodes. There is no consensus on the exact nature of the yellow substance or the implications of the observed reactions.

Contextual Notes

Participants discuss the roles of different ions and materials in the electrolysis process, but there are unresolved assumptions regarding the specific reactions and the behavior of the materials used.

Who May Find This Useful

Individuals interested in electrolysis, chemical reactions in aqueous solutions, and experimental setups involving electricity and water may find this discussion relevant.

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So, today I was bored and decided to play around with some water and electricity. I took a 9v battery and attached 2 steel wires at both terminals, then I attached 2 steel screws to the ends of the wires. I used a bit of NaCl to speed up the process too.

When I placed the electrodes in the water, only the anode was producing any gas, while the cathode was doing absolutely nothing. After several seconds (maybe 45 or so) the water turned a yellow color (almost like chlorine) and has small suspensions inside it. What happened? The yellow color couldn't be cl2 could it?

Maybe the steel reacted strangely with something in the water?

Maybe the Cl is reacting with the iron cathode?
 
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this is the most common and important electrolysis. at the anode Cl^- are oxidized to yellow Cl_2 (g). at the cathode, the halv reactions involves water molecules, which are easier to reduce than sodium ions. the cathode will forme hydrogen gas. so the solution around this electrode becomes basic
 
Chlorine is not that soluble in water to not evolve, and even when dissolved, it doesn't substantially change water color. Sounds to me more like you have been dissolving electrode material.
 
Borek said:
Chlorine is not that soluble in water to not evolve, and even when dissolved, it doesn't substantially change water color. Sounds to me more like you have been dissolving electrode material.

Yeah, I think you're right, I changed the electrodes to carbon, which has eliminated the problem, now I'm getting H2 O2 at the correct places now.

So what do you think happened? The chlorine was reacting with the iron forming iron (III) chloride?
 

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