Questions tagged [electrolysis]

For questions about the chemical concepts of electrolysis.

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20 votes
7 answers
51k views

Why can't pure water conduct electricity since it can be reduced at cathode and oxidised at anode?

We all know that pure water can't conduct electricity. But during electrolysis, if add a small amount of $\ce{HCl}$ acid inside, water could be decomposed to hydrogen gas and oxygen gas, as it is ...
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2 votes
1 answer
5k views

Copper chloride color in electrolysis of salty water

I tried a simple water electrolysis experiment at home, with $\ce{NaCl}$ as electrolyte, and a $12 \,\rm{V}$ battery. My wires were made of copper and $\ce{H2}$ bubbles were only forming at negative ...
10 votes
3 answers
11k views

Why is chloride oxidised instead of water in copper chloride electrolysis?

For the Electrolysis of Copper Chloride: Cathode: $\ce{Cu^{2+} + 2e- <=> Cu}$ Anode: $\ce{2Cl <=> Cl2 + 2e- }$ I am confused about the reaction taking place at the anode. Wouldn't $\ce{...
10 votes
2 answers
6k views

How can I identify whether a substance is KOH or NaOH?

I've bought $\ce{NaOH}$ or $\ce{KOH}$ (I don't remember which one!) for my electrolyzer and I've tested it. Now I want to improve its performance and I was searching for a better electrolyte when I ...
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6 votes
3 answers
2k views

In my homemade electrolysis setup, only the negative end bubbles?

I've created an electrolysis setup by connecting a $6~\mathrm{V}$ battery to a cup filled with saline water via pencils; I am confused as to why only the negative pencil bubbles though. After running ...
8 votes
2 answers
8k views

Why do positive ions go to the cathode?

In electrolysis why do positive ions go to the cathode? Since the cathode is positive, won't the positive ions face repulsion at the cathode and would require more energy? I understand that reduction ...
  • 97
7 votes
2 answers
5k views

Creating ethane through electrolysis of vinegar

Some sources that I studied say that it is possible to produce ethane through the electrolysis of ethanoic acid. Would this work with vinegar (5-10% acid)? Also, other sources say that ethanoate ...
6 votes
2 answers
26k views

Electrolysis of aqueous copper (II) nitrate

There are two copper blocks sitting in the $\ce{Cu(NO3)2 (aq)}$ solution, a battery is attached onto both of them, providing enough energy to start the reaction. Since solid pieces of copper are ...
  • 257
5 votes
3 answers
7k views

Can I perform electrolysis without electrolyte? (with distilled water)

When performing electrolysis at home, I usually used salt water as electrolyte. The problem is, that this method also produces chlorine and chlorine is aggressive to both humans and electrical ...
  • 2,326
4 votes
1 answer
282 views

Is there an electrolyte that will halt the production of Hydrogen in water electrolysis?

Care must be taken in choosing an electrolyte, since an anion from the electrolyte is in competition with the hydroxide ions to give up an electron. An electrolyte anion with less standard electrode ...
  • 49
2 votes
1 answer
917 views

High voltage AC water electrolysis not working

I was trying to use a $500~\mathrm V$ AC power supply to split water, but nothing happened. I tested everything with a $9~\mathrm V$ battery, and it all worked fine. Why did it not work with the ...
  • 49
2 votes
1 answer
9k views

Reaction of sulfate ion in copper sulfate electrolysis

I am planning to try copper plating a piece of metal by performing electrolysis on an aqueous solution of copper sulfate. I plan run an electrical current with the metal I want to plate as the cathode ...
1 vote
1 answer
3k views

Electrolysis in aqueous solution – which equations to use to predict product at each electrode?

When trying to work out what will be produced at each electrode during electrolysis, I'm confused as to which equations to use for hydrogen and oxygen. For instance, an electrolytic cell containing ...
  • 13
12 votes
7 answers
20k views

Does NaOH react with K to form NaOK or KOH?

I realized that the $\ce{-OH}$ group when it reacts with some metal like $\ce{Na}$ or $\ce{K}$ will replace the $\ce{H}$ element to form $\ce{-OK}$ or $\ce{-ONa}$: \begin{align} \ce{H2O + Na &...
  • 727
12 votes
4 answers
28k views

How does high-frequency electrolysis of water work?

I have read that combining the DC current with a high-frequency AC current, the electrolysis of water speeds up. Is this true? In that case, how is less energy wasted as heat? Or does it simply ...
10 votes
4 answers
6k views

Which electrodes do not corrode at all?

I had used spare pieces of metal to perform electrolysis. They all had the disadvantage that they corrode when used as anode - and some of the oxides are toxic (copper, chromium). I've found that ...
  • 2,326
8 votes
2 answers
1k views

Can "Common Ion Effect" suppress the dissociation of water molecules in acidulated water?

$$\begin{align} \ce{H2O &<=> H+ + OH-} \\ K &= \frac{[\ce{H+}][\ce{OH-}]}{[\ce{H2O}]} \\ \ce{H2SO4 &<=> 2H+ + SO4^2-} \end{align}$$ In acidulated water water dissociates into ...
8 votes
4 answers
28k views

Why do they use graphite electrodes in the Hall–Héroult process?

In the Hall–Héroult process of extracting aluminium from aluminium oxide, the electrolyte is a liquid mixture of cryolite $(\ce{NaAlF6})$ and aluminium oxide $(\ce{Al2O3}).$ The cathodes and the ...
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7 votes
1 answer
238 views

Electrolysis puzzle

I created an electrolysis setup to study how different electrolytes, their concentrations, and the electric current affect the "speed" of the electrolysis process. With that in mind, I built a simple ...
6 votes
1 answer
2k views

Electrolysis of Beer

Electrolysis of water, means that the water is separated into hydrogen and oxygen. As beer also includes water, I initially thought electrolysis of beer would cause the water to separate, and the ...
  • 161
5 votes
1 answer
804 views

Why are electrolysis cell plates turning a brown color?

I have been experimenting with electrolysis for producing oxyhydrogen and using potassium carbonate $(\ce{K2CO3})$ as an electrolyte. After several hours of electrolysis, I noticed that the plates ...
5 votes
1 answer
3k views

Can every conductor be electroplated using copper and sulphuric acid?

I really like electrolysis. Today I bought 30% sulphuric acid to electroplate something with pieces of copper. I've poured half water and half acid in a glass. I connected some cuprextit-copper plate ...
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4 votes
1 answer
1k views

What is the greenish substance formed after the electrolysis of two graphite electrodes in a sodium sulphate solution?

Today at school we tried the electrolysis with two graphite electrodes in a sodium sulphate solution. We put the electrodes in two test tubes and filled them with some more sodium sulphate so that the ...
  • 51
4 votes
1 answer
197 views

Do ion-exchange membranes *always* require ions to pass in both directions?

In an answer to this question, it was asserted that: Student always tend to forget that a solution must remain electrically neutral by all means. If you want a certain ion to leave water, you must ...
  • 189
4 votes
1 answer
868 views

Whats the effect of pressure on water electrolysis of sea water with increase in depth?

I’m currently working on an underwater robot and was hoping to use the gas bubbles produced by water electrolysis for buoyancy control. The operating depths range from 200–1000 m.
4 votes
2 answers
6k views

Extracting sodium from salt

At my school, my teacher tell us to extract sodium from normal salt ($\ce{NaCl}$) but without using electrolysis of molten sodium chloride. So is there a way to do that?
4 votes
1 answer
200 views

Soil batteries?

In an attempt to demonstrate the basic principles of common batteries, my teacher assigned me to demonstrate a simple experiment to the kids at the elementary school. A tank filled with saltwater, ...
3 votes
1 answer
2k views

What are possible side reactions for the generation of hydrogen via electrolysis?

I recently completed making a simple water electrolysis setup to generate hydrogen which uses two graphite rods from a standard AA battery. The power source is a $24~\mathrm{V}$ $6~\mathrm{A}$ adapter....
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3 votes
1 answer
326 views

Electrolysis on aqeuous solution

I know when electrolysis on a concentration aqeuous solution which contains halide ions($Cl^-$ , $Br^-$ , $I^-$). The halide ions is discharged although $OH^-$ is more easily to discharged. For ...
3 votes
1 answer
4k views

Why can't sulphate ion be discharged in the anode of electrolysis?

Given that there is an aqueous solution of sulfuric acid ($\ce{H2SO4}$), $\ce{2H+}$ is reduced in the cathode and $\ce{OH-}$ is reduced in the anode. Why is $\ce{OH-}$ preferentially discharged over $\...
3 votes
3 answers
8k views

Is it dangerous to inhale the steam coming from electrolysis of salt-water solution [closed]

Is chlorine in there that accumulates (at the anode) and emerge out as chlorine gas? I was worried since I added a pinch of salt to the steamer in order to hasten the heating of tap water when I ...
3 votes
2 answers
515 views

Is it possible to have electric field in water without having electrolysis?

Is it possible to have electric field in water (using electrodes with voltage difference) without having electrolysis in the water (or any other reaction)?
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3 votes
1 answer
1k views

Deuterium removal from water

What percentage of deuterium might be removed from water after a typical electrolysis procedure? From a post on this site I read that, "In the first stage, $\ce{NaOH}$ solution (initially $0.5\rm{M}$) ...
  • 31
2 votes
2 answers
86 views

Kolbe's electrolysis reaction for alkenes' production

I came across a question in which the major product was asked for Kolbe's electrolysis of potassium salt of 2,3-dimethylbutane-1,4-dioic acid. The answer was given as trans-(but-2-ene). I couldn't ...
2 votes
2 answers
491 views

What an electrolyte "really" does in electrolysis?

I am reading about electrolysis and I have trouble to understand why an electrolyte must be added in order for electrolysis to occur. I have read this question but still can't get it. The definition ...
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2 votes
1 answer
127 views

Non-zero current flow through an electrolytic cell, when an electric potential lesser than that needed for electrolysis is applied?

For instance, the potential needed for water splitting is $\pu{1.23V}$. However, there is current flow even at lower potentials (say $\pu{0.5V}$). Clearly, there is no redox reaction happening in the ...
2 votes
2 answers
5k views

Why is reduction potential of water ( 2H₂O + 2e⁻ → H₂ + 2OH⁻ ) is -0.83 insted of 0, as in the case of (2H⁺ → H₂)?

I came across this value of reduction potential of water while solving a question. Also, I noticed that, for example $$\ce{Ag+ → Ag}$$ has a fixed standard potential, and the same is used when we do ...
2 votes
1 answer
182 views

Why would water, and not saltwater, undergo electrolysis?

I am attending a cram school and there was a question that goes: Electrolysis decomposes chemicals by passing an electric current through a liquid or solution containing ions. Which of the ...
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2 votes
1 answer
834 views

Electrolysis with baking soda solution, a penny as the cathode and graphite for the anode

I set up an electrolysis experiment to show my kids and wanted to explain to them what is happening. My setup has a penny as the anode and graphite for the cathode. The solution is water with baking ...
2 votes
0 answers
598 views

Copper (II) oxide during CuSO4 electrolysis

I was performing copper (II) sulfate electrolysis (graphite electrodes; 10V; 0,01A) today and I observed black precipitate falling from around cathode. I suppose it's copper(II) oxide. I couldn't find ...
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2 votes
1 answer
12k views

how is the relation between Gibbs free energy and cell potential?

First of all what is exactly Gibbs free energy in regards to an electrochemical process? How can we visualise it? How does Gibbs free energy change in an electrochemical reaction? How is it related to ...
2 votes
1 answer
1k views

Can a strong electrolyte be sparingly soluble? [duplicate]

A strong electrolyte is an electrolyte that completely, or almost completely, ionizes or dissociates in a solution. My book has a question: In a saturated solution of sparingly soluble strong ...
2 votes
1 answer
2k views

Products of Electrolysis of NaCl

I have gone online to see many times that the electrolysis of $\ce{NaCl}$ dissolved in water produces Lye: $$\ce{2NaCl + 2H2O -> 2NaOH + H2 + Cl2}$$ Other times $\ce{NaClO3}$ or some other compound....
1 vote
1 answer
201 views

Is this galvanic cell representation right?

Question 13. In the galvanic cell: $$\ce{Pt(s) | I2(g) | I-(aq) || Fe^3+(aq) | Fe^2+(aq) | Pt(s)}$$ Representation of anode is incorrect and cell will not work. $[\ce{Fe^3+}] = [\ce{Fe^2+}] = [\ce{I-...
1 vote
2 answers
1k views

Electrolysis with two similar metals

I've researching electrolysis recently, and all of the examples I've seen use two different metals as the cathode and anode. In my attempts to make a hydrogen producing cell (table salt used as the ...
1 vote
1 answer
8k views

Best Settings for Electrolysis of water

I want to electrolyze water as a personal project, but I have found conflicting power recommendations on google. Some sources recommended a higher voltage, claiming that higher amps will just destroy ...
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1 vote
1 answer
836 views

What is the benefit of high surface area electrodes?

Some electrolytic apparatus is equipped with high surface area electrodes. The number of reduced/oxidized atoms is proportional to the total charge flowing through the cell. Does increasing surface ...
  • 1,462
1 vote
5 answers
11k views

Does the electrolysis of water produce chlorine gas?

http://orbitingfrog.com/2014/11/02/electrolysis-of-water-with-pencils-and-a-9v-battery/ This article seems to indicate that "a small amount of Chlorine may be produced as you [perform electrolysis on ...
0 votes
1 answer
2k views

How do electrolytes allow electrolysis to occur?

From what I know, when two electrodes are places in a electrolyte (say $\ce{H2SO4}$, which decomposes into $\ce{H}^{+}$ and $\ce{SO4}^{2-}$ in aqueous solution), the negative ion is attracted to the ...
0 votes
2 answers
917 views

Electrolysis of sodium chloride solution [closed]

I am trying to understand electrolysis. My question is: when electrolysis is done with a NaCl solution I have learnt that sodium metal is not formed. Why is this?
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