Questions tagged [electrolysis]

For questions about the chemical concepts of electrolysis.

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17
votes
7answers
45k 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 ...
14
votes
5answers
8k views

Does increasing concentration of copper sulfate decrease or increase its conductivity?

I am a high school student and for my chemistry lab, I did an electrolyis experiment on how the changing concentration of electrolyte (copper sulfate) will change the rate at which the copper is ...
13
votes
5answers
23k views

How does High Frequency water electrolysis 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
2answers
4k 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 ...
10
votes
4answers
4k 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 ...
10
votes
1answer
571 views

Oxidation of aluminum and manufacturing of electrolytic capacitors

My background is in electrical engineering. Recently I saw instructions on how to manufacture electrolytic capacitors at home by mixing sodium bicarbonate (baking soda) to distilled water, submerging ...
10
votes
1answer
837 views

carbon electrodes have potential difference even with no electrical input?

What is happening in this photo? I set up a simple electrolytic cell today of copper (II) sulfate solution with carbon electrodes. It was connected to a powerpack (set at ~8.0V), and a variable ...
9
votes
2answers
474 views

Why do we do electrolysis and electroplating using warm electrolyte?

This is a pretty basic question, and I know it has something to do with conductivity, but I'm not quite sure how they are related.
9
votes
3answers
8k 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{...
9
votes
0answers
220 views

Does a zinc metal coating react with coffee in a coffee grinder?

I'm restoring an old coffee grinder and I want to give the grinder mechanism a nice zinc / silver coating. But I read it is not safe for zinc to be in contact with acidic foods. When I look at the ...
9
votes
2answers
1k views

Cathode gained mass in zinc electrolysis

I performed an electrolysis of zinc, using two zinc electrodes and a zinc nitrate solution. However, after leaving the electrolysis to run for 30 min, at about 0.4 A and 6 V, I discovered that the ...
8
votes
2answers
4k 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 ...
8
votes
2answers
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
2answers
3k views

Do water hybrid cars really exist?

I have heard a few claims about water-fueled cars. Being a student of Engineering I totally understand that water-fueled cars (using electrolysis to generate Hydrogen) are nothing more than a hoax, ...
8
votes
1answer
6k views

Relationship between surface area of electrode and reaction rate of hydrogen in fuel cells

I am looking at the effects of increasing the surface area of which the flowing hydrogen fuel is in contact with the anode in a fuel cell. At the anode the hydrogen is catalytically split into ...
8
votes
1answer
3k views

Possible methods for copper (II) reduction to copper (I)

How can I make $\ce{Cu2O}$ from copper? I am seeing if electrolysis is a good route (in the context of kitchen style chemistry) to cuprous oxide, instead of the traditional heating copper and ...
7
votes
1answer
537 views

Why does electrolysis of aqueous concentrated sodium bromide produce bromine at the anode?

It is often stated that electrolysis of any aqueous concentrated halogen compound will produce the halogen at the anode, despite it having a more postitive standard electrode potential than the ...
7
votes
2answers
4k 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 ...
7
votes
1answer
627 views

How can I dispose of chlorine and sodium hydroxide as table salt and water?

If I used chloralkali electrolysis of brine to produce hydrogen, and can't use the other products (or not all of them), what route(s) can I take to revert them back to brine? I figured, since I have ...
7
votes
3answers
20k views

Why would hydrogen not be generated at the cathode when electrolysing zinc sulfate?

Describe how zinc metal can be obtained from zinc sulfate solution by electrolysis. A labelled diagram is acceptable. Include all the products of this electrolysis. The electrolysis is similar to ...
7
votes
2answers
652 views

Cell overpotential diagrams

Is there anyone who knows a book where I can find a detailed explanation of cell overpotential diagrams, like the ones shown here? Thanks in advance!
7
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2answers
1k views

Nernst equation for a fuel cell when gases are stored separately

I have run some tests with a PEM fuel cell and the voltage we have found was $1.44\ \mathrm{V}$. Given that the standard potential for a fuel cell is $1.229\ \mathrm{V}$ what is causing the difference ...
6
votes
2answers
15k views

How does voltage and resistance affect an electrolysis?

At school we've learned about calculating the voltage needed to perform an electrolysis. The current is how many electrons pass per time. The formula is given $$I = \frac UR$$ This means that given ...
6
votes
2answers
16k views

Why does decreasing the distance between the electrodes in an electrolytic cell increase the rate of electroplating?

I did an experiment on the effect of the distance between the electrodes on the rate of electroplating in an electrolytic cell (copper electrodes with copper sulfate electrolyte). As I expected, when ...
6
votes
1answer
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 ...
6
votes
1answer
153 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
1answer
1k views

Will KOH work in place of NaOH as the electolyte in the electrolysis of water?

I am making a hydrogen and oxygen generator by electrolysis water. I found out that using salt as an electrolyte creates a compound of chlorine and oxygen with my electrodes clouding up the water and ...
6
votes
2answers
1k views

Change in current in an electrolytic cell over time

Why does the current increase over time in an electrolytic cell with a $\ce{CuNO3}$ electrolyte. The current increased about $2~\mathrm{A}$, and the temperature increased during the experiment to ...
6
votes
1answer
21k views

Salt concentration and electrical permittivity of water

We know that the electric flux density $D$ can be related to electric field intensity $E$ as $D=\epsilon(\omega) E$ $\epsilon(\omega) = \epsilon_0 \epsilon_r(\omega) $ where $\epsilon_0$ is the ...
6
votes
3answers
770 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 ...
6
votes
1answer
1k views

Why soak filter paper in K2SO4?

From a description of my experiment: Potassium iodide crystals are place in the middle of filter paper soaked with potassium sulphate and phenolphthalein. Two electrodes are placed on the filter on ...
6
votes
1answer
134 views

If liquid hydrogen fluoride autoionises, how can it be an insulator?

According to Wikipedia, one of the last major hurdles in the isolation of elemental fluorine was the need to mix hydrogen fluoride with another substance in order for its electrolysis to be possible (...
6
votes
3answers
5k views

What can be used as an electrolyte in water to perform electrolysis other than salt?

I am looking for an electrolyte to use in water to perform electrolysis. It can't be salt, as salt ($\ce{NaCl}$) would cause the chemical reaction of $$\ce{2H2O + 2NaCl -> Cl2 + H2 + 2NaOH}$$ or ...
6
votes
2answers
5k views

What current and voltage are best for electrolysis rust removal?

I weld carbon steels all the time, and sometimes I get parts from the scrapyard. Unfortunately, these parts are generally oxidized, so I've been assembling an electrolysis tank for it. This tank ...
6
votes
2answers
962 views

Nernst equation and electrolysis

Let's say we have a stable solution of $\mathrm{A}_{\left(\mathrm{aq}\right)}^{2+}$ and $\mathrm{C}_{\left(\mathrm{aq}\right)}^{+}$ , with their respective counter-ions. The associated redox ...
6
votes
0answers
272 views

How much CO2 is created during water electrolysis with a graphite anode?

I'm experimenting with water electrolysis and wanted to use non-toxic materials, so I settled on pure graphite rods for both electrodes and Epsom salt (magnesium sulfate) as the electrolyte. The ...
5
votes
2answers
14k views

What's happening to carbon electrodes?

Carbon electrodes are very popular, because unlike metal electrodes, carbon is quite inert during electrolysis (I'm sure that has some explanation based on electronegativity). However they too are ...
5
votes
1answer
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 ...
5
votes
2answers
409 views

Is it safe to inhale O2 from electrolysis of a pH 13.7 KOH solution?

I'm conducting electrolysis of water with a 0.25M KOH solution in water (about 14 on my pH meter) using graphite electrodes, and I was wondering if the O2 would be safe to inhale, as in an oxygen bar?
5
votes
1answer
1k views

What is the heat energy required to perform electrolysis equivalent?

The question may be off-topic here. If my concept is flawed, please poke me in the rib (+: Sources on the internet indicate a minimum 1.2Volts is adequate for electrolysis of water; nominally 6V. ...
5
votes
1answer
157 views

Will oxidation/reduction of copper still occur in an electrochemical cell if it is not in an aqueous environment?

Notation of the reduction and oxidation of copper typically includes the aqueous state. Illustrated below: $$\ce{Cu(s) -> Cu^2+(aq) + 2e-}$$ This event usually occurs at 0.34 V. What if the copper ...
5
votes
2answers
490 views

Formation of species in electrolysis

I understand the principles of electrolysis of salts in aqueous solutions, but there are two points on which i am unsure. At the positive electrode, how can you work out which ions will ...
5
votes
1answer
490 views

Electrolysis Lab

How do I keep hydrogen or oxygen in a test tube when pulling them out of water? I have a Styrofoam cup with two metal thumbtacks pushed though the bottom, and about 100 ml of distilled water mixed ...
5
votes
1answer
498 views

Electrolysis of water for demonstration: ideal electrolyte for safety, stability, conductivity, and ease of maintenance

I'm developing a system for educational purposes where electrolysis of water takes place. The aim is to practically show how electrical energy can be converted to mechanical, by electrolyzing water, ...
5
votes
1answer
141 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, ...
5
votes
1answer
189 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 ...
5
votes
1answer
157 views

Change of potential difference during electrolysis while adding salt

I was conducting a simple experiment at home on electrolysis. Obviously, when you build a circuit with a 9V battery, a lamp, and put two electrodes in water you measure a potential difference of ~9V ...
5
votes
0answers
119 views

Thought Experiment: Is it possible to preserve the charge imbalance present during molten lead(II) bromide electrolysis?

Suppose I were to electrolyse some molten lead(II) bromide. According to what I have been taught, the lead ions travel towards the cathode and are reduced at it, while the bromide ions are oxidised at ...
5
votes
0answers
80 views

Autocatalysis / Electroless plating of mercury

As a project I am trying to plate mercury onto a powdered metal amalgam of $\ce{Cu}$ & $\ce{Ag}$. I am using solution of $\ce{HgCl2}$ in normal $\ce{HCl}$ (a reducing agent), Any thoughts for ...
5
votes
0answers
263 views

Reduction of vanadyl ion

I want to reduce vanadyl to vanadium (III), can somebody please suggest some appropriate methods for it? I am trying to make a redox flow battery for a project but I have only vanadyl sulfate.