20 votes
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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 ...
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19 votes
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How can I identify whether a substance is KOH or NaOH?

A flame test should tell you pretty quickly. Make a small wire loop (preferably steel or nichrome), heat in a bunsen burner or propane torch flame until red hot and all the contaminants are burned off,...
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  • 9,036
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 ...
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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 ...
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13 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 ...
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11 votes

Can water be produced by mixing hydrogen gas and oxygen?

Indeed, it's called combustion! When you burn hydrogen and oxygen gas, the reaction is: $$\ce{2H2_{(g)} + O2_{(g)} -> 2H2O_{(g)} + energy}$$ Basically, you could see the former U.S. space shuttle ...
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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 ...
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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-...
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11 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 ...
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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 ...
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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 ...
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10 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 - ...
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9 votes
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Which electrodes do not corrode at all?

This highly depends on what you are electrolyzing. When using solutions that are not very acidic, oxide-coated metals sometimes work, like lead-oxide electrodes, that can be harvested from old lead ...
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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 ...
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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 ...
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8 votes
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Can every conductor be electroplated using copper and sulphuric acid?

While you can use basically any conductive material as an electrode to reduce the metal ions in solution, to actually plate the electrode with the metal, the metal has to be able to attach to the ...
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8 votes

Electrolysis of Beer

It's hard to say what exactly you would end up with, but it probably wouldn't much resemble beer. The trick with electrochemistry is that a lot of things are electroactive and what reactions actually ...
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8 votes

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

It's a bit of an oversimplification to explain this with a simple invocation of Ohm's law. The thing to remember about electrochemistry is that electron transfer only happens at every close distances ...
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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 ...
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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 ...
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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 ...
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7 votes

Which electrodes do not corrode at all?

you do not need to solder a graphite electrode to connect it. It is possible to connect mechanically (screws, wires etc.). It is possible to buy some bigger pieces here: Penta trading To answer your ...
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7 votes

Reduce chlorine gas

The issue is that oxidation of chloride to chlorine has a lower overpotential than oxidation of water to oxygen. You will always have to have an oxidation reaction going on while reducing water to ...
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7 votes
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While electrolyzing concentrated aqueous sodium chloride, why is it that chlorine is discharged but not sodium?

Let's take a look at a table of standard electrode potentials and find the relevant half-reactions: Reductions (there is also a half-reaction for water reduction that doesn't involve a proton at -0....
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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 ...
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