20 votes
Accepted

Can electrodes be made from mercury?

The dropping mercury electrode (DME) is a working electrode made of mercury and used in polarography. Experiments run with mercury electrodes are referred to as forms of polarography even if the ...
Aryan's user avatar
  • 693
19 votes

Why do positive ions go to the cathode?

TL;DR The cathode in an electrolytic process is considered to be negative, so there is actually no contradiction. The cathode is a positive electrode in a galvanic cell. There are different notations ...
andselisk's user avatar
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15 votes

Why is twice as much hydrogen produced than chlorine in the electrolysis of brine?

It appears, as the others have said that the same number of moles of gas of chlorine and hydrogen is produced. Then why are there different levels of solution? Since the solution is taken out in the ...
14 votes

How to control current and voltage in electrolysis

You can't control both voltage and current electrically: Your power supply will hold one or the other constant, but the properties of the electrolytic cell will then determine the other one. So you ...
Bob Jacobsen's user avatar
14 votes

Tin(II) chloride electrolysis problems: (1) Why is the tin dendritic? (2) Why does the unconnected metal in the middle also act like an electrode?

I have done this experiment plenty of times with my students. It is one of my favorites. The results are surprising, and often difficult to reproduce. It depends on the current. With a low current $(I ...
Maurice's user avatar
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14 votes
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Is there any process that converts water into hydrogen and oxygen by using light and a catalyst?

Probably several of them. The one I found at the top with a search for "photocatalytic water decomposition" is Ref. [1]: The photocatalytic activity for water decomposition of alkaline ...
Oscar Lanzi's user avatar
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13 votes
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What happens to an ongoing electrolysis when you turn off the battery?

This is a very good question! I'm not sure why you received a downvote. What you are asking about is called a polarization current. Suppose we are electrolyzing a solution and suddenly we stop the ...
AChem's user avatar
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12 votes

High voltage AC water electrolysis not working

Alternating current (AC) is your problem. AC spends half its time pushing electrons forward through the circuit, and half the time pushing them in reverse through the circuit. Thus, on average the ...
hBy2Py's user avatar
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12 votes

Electrolysis with salt water on steel plates creates horrible black liquid

The applied current drives sodium ion to the cathode (negative pole) where hydrogen is evolved and the surrounding medium becomes more alkaline. The more interesting - in the sense of catastrophic - ...
James Gaidis's user avatar
11 votes

Does NaOH react with K to form NaOK or KOH?

The question: Will $\ce{NaOH + K}$ form $\ce{NaOK}$ or $\ce{KOH}$? This is a redox reaction regardless of what species $\ce{K}$ would react with. The answer is two-fold: (a) Having potassium added to ...
Mathew Mahindaratne's user avatar
11 votes

Why is twice as much hydrogen produced than chlorine in the electrolysis of brine?

I'm not sure how the first diagram shows a $2:1$ volume ratio. But I am sure about the balanced chemical equations: $$ \begin{align} \ce{2 Cl^- &→ Cl2 + 2 e-} \\ \ce{2 H2O + 2 e- &→ H2 + 2 OH-...
Oscar Lanzi's user avatar
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11 votes
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Homemade diode working mechanism

When aluminum is the anode (connected to the positive battery terminal), a thin layer of insulating aluminum oxide is produced via the “anodization”. It serves as a dielectric, so basically you have a ...
Ed V's user avatar
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10 votes
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Why does electrolysis of aqueous concentrated sodium bromide produce bromine at the anode?

There is important to know the actual potential depends on actual activities of reagents ( approximately concentrations for dilute solutions). Additionally, the electrode potential is the ...
Poutnik's user avatar
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9 votes
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Why a low conductance ion such as lithium is used in batteries?

The conductivity values you cite are for ions in water. there is no water in a lithium battery otherwise, it would explode and burn before leaving the factory. Beside low conductivity can be ...
A.K.'s user avatar
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9 votes

Can electrodes be made from mercury?

Related only - but posted as an answer as, while not 100% what you asked about, it's related enough to be worth noting. In the past some angle detection or motion detection switches used rolling ...
Russell McMahon's user avatar
9 votes
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Orientation of external cell when voltage is supplied by it to voltaic cell so as to oppose its cell potential

The figures in the OP's post are nicely drawn, as expected in a modern textbook, but figure 3.2(c) has the external battery reversed, which is incorrect. Here is how it works, without the needless ...
Ed V's user avatar
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8 votes
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Can "Common Ion Effect" suppress the dissociation of water molecules in acidulated water?

You have a couple of concepts mixed together in the wrong way. (1) The ionization of water is typically written as $\text{K}_\text{w} = \ce{[H+] \cdot [OH^-]}$ The assumption is that the ...
MaxW's user avatar
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8 votes

Why do we do electrolysis and electroplating using warm electrolyte?

ringo makes good points in his answer. Additionally, though, the increased temperature enhances mass transfer of ions to/from the electrode surfaces by at least two mechanisms: Higher temperature ...
hBy2Py's user avatar
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8 votes
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Voltage needed for electrolysis of water

I'm assuming you mean this Wikipedia article on the hydrolysis of water in which the method of determining that potential difference is described farther down the page. I'll address your other ...
Ben Norris's user avatar
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7 votes

Creating ethane through electrolysis of vinegar

Indeed that is quite possible. The reaction was first described by Hermann Kolbe and is hence called "Kolbe's Electrolysis" It is a decarboxylative dimerisation of two carboxylate ions (carboxylate ...
getafix's user avatar
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7 votes
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Why are electrolysis cell plates turning a brown color?

Since the carbonate radical is covalently bonded, it probably is not being decomposed electrolytically. Much more likely is that iron in the stainless steel is being removed and oxidized, leaving a ...
DrMoishe Pippik's user avatar
7 votes
Accepted

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

Your setup, using table salt ($\ce{NaCl}$ plus additives) will initially electrolyse according to the following two reactions, separated by cathodic reduction and aniodic oxidation: $$\ce{2 H+ + 2 e- ...
Jan's user avatar
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7 votes
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Why do we do electrolysis and electroplating using warm electrolyte?

The reasoning here is two-fold. The solubility of most electrolytes increases with temperature, and water's ionization constant also increases with temperature. On the whole this means more ions, and ...
ringo's user avatar
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7 votes

Why do positive ions go to the cathode?

You got it reversed. The cathode is the electrode where cations discharge, hence the name. BTW, effective electron flow in galvanic cells is always directed from the cathode to the anode. The '...
permeakra's user avatar
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7 votes
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Oxidation of aluminum and manufacturing of electrolytic capacitors

You are performing an electrolysis. This means that on the (+) electrode de reaction is Al $\rightarrow$ Al$^{3+}$ and on the (-) electrode the reverse occurs. Distilled water is required to avoid ...
Raoul Kessels's user avatar
7 votes

Electrolysis puzzle

As is often the case with chemistry, you can't ignore the fact that your instruments are also made of atoms and have a chemistry of their own. Naturally, in this setup you just dissolve copper from ...
Ivan Neretin's user avatar
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7 votes

Pressure-dependence of electrolysis voltage

Of course, we're starting by acknowledging a perpetual motion machine is impossible. The question, then, is how do we understand, through chemical thermodynamics, why your specific set of steps can't ...
theorist's user avatar
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7 votes
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Can sulfuric acid itself be electrolysed?

After some searching, I found this 1956 Thesis(Reference), which describes the production of peroxydisulfuric by electrolyzing concentrated sulfuric acid. The yield varied according to the ...
Nilay Ghosh's user avatar
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7 votes

How does liquid gallium interact with a gold leaf

Broadly speaking, looking at the Au-Ga phase diagram one gets: (Now, this is based on a paper from 2011, a more recent 2017 paper is open access). Several things to notice (or get from the paper): ...
Jon Custer's user avatar
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7 votes
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What does the salt actually do during electrolysis?

A salt like $\ce{Na2SO4}$ is essential in electrolysis. It provides ions $\ce{Na+}$ and $\ce{SO4^{2-}}$ which are attracted by the electrodes in the solution and migrate to them. When they arrive near ...
Maurice's user avatar
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