# Tag Info

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First of all, have a look at the wikipedia page on electrolysis of water. I also like this review: Zoulias et al.: A Review on Water Electrolysis, TCJST, 4 (2) (2004) 41-71 Specifically they list a number of actually existing installations (context: renewable energy) and their actually achieved efficiency. Speed up does not necessarily have anything to do ...

20

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 experiments are identical or very similar to a corresponding voltammetry experiment which uses solid working electrodes. Like other working electrodes these ...

19

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, then dip it in your solution and put it in the flame. If sodium is present, you should get a bright yellow flame, and if it is potassium, the flame will be a ...

19

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 for the sign (±) of the cathode used in the literature, which are determined, in particular, by the nature of the process. A very broad definition of a cathode ...

15

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 cathode chamber, the level of solution present is lower than the anode chamber where sodium chloride solution is being added in.

14

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 need to hold all of the chemical parts of the experiment constant: Have a large ion bath so that the concentration doesn't change much as the plating takes ...

13

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 $(I < \pu{0.05 A}),$ long, bright and thin metallic needles are obtained starting from the cathode. They sometimes touch one another in the middle of the box, ...

11

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 as a large machine that turns hydrogen and oxygen into water. (Note: the space shuttle used liquid hydrogen and oxygen, but otherwise the principle and formula ...

11

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 an aqueous solution of sodium hydroxide; and (b) Having potassium added to molten sodium hydroxide, therefore no water present (or trace amount). Answer to ...

11

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-} \\ \hline \ce{2 H2O + 2 Cl- &→ H2 + Cl2 + 2 OH-} \end{align} Thus equal amounts of both gases are produced, and at the same temperature and pressure ...

11

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 leaky capacitor: current is low. But when the aluminum is connected to the negative terminal, it is the cathode and then you get reduction of hydrogen ions to ...

10

From the comments, mcocdawc: Was it DC or AC? OP: AC. I was trying to see if it was possible. There's your problem. Alternating current 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 net current pushed through the cell is zero. So, leaving aside ...

10

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 thermodynamic quantity. If some net reaction kinetic is involved, other potentials affects the actual potential at the solution border, like the diffusion potential and ...

9

Voltage determines the kind of chemistry at each electrode. Gold is purified by plating the anode to the cathode at minimum voltage for the half-reaction, so impurities either do not dissolve and do not plate out. Copper electrorefining electrode mud contains valuable trace elements in concentrated from. Current determines the amount of chemistry, ~96,500 ...

9

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 accumulators (attention, lead is toxic, wear lab coat and gloves when working with them. Lead accumulators contain ~20% sulfuric acid, so wear gloves as well and ...

9

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 compensated by increasing concentration of the ions or a variety of other architectures. Further, there's a few reasons lithium is optimal in batteries. It's not ...

9

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 mercury as a bridge between two metal contacts. The term "Mercury switch" was commonly used. The Mercury is necessarily inert relative to the associated ...

8

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 surface. If you have contaminants like surfactants, it can prevent deposition. The trouble with using aluminum as a cathode is that it readily forms an oxide layer ...

8

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 occur in a given reaction are not always easy to predict and depend on electrodes, solution composition, pH, applied potential, etc. Depending on your ...

8

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 ionization is so low that the concentration of water remains a constant. For a solution which is half water and half acetic acid that wouldn't be true of course. (2) ...

8

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 results in lower electrolyte viscosity, leading to a thinner fluid dynamic boundary layer and concomitant greater mass transfer to/from the electrode surfaces. ...

8

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 questions - what might cause this value to change. Volume No, except see below on concentration. The reaction potential for this electrolysis is independent of ...

7

From the site that you linked: A battery would be used as a source of electrical energy which would separate the hydrogen/oxygen into gases. The gasses would then fuel an internal combustion engine, which would power a generator to continously recharge the battery as well as deliver useable mechanical energy. If this sort of motor can be made to work, the ...

7

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 question: Platinum is really hard to corrode. It is commonly used platinum coated titanium mesh, but it is quite expensive. link: Alibaba

7

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 hydrogen. The one with the lowest standard potential + overpotential will win. The reason the overpotential exists is that electrolysis is pushing the system away ...

7

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 -0.83 V, but for the sake of simplicity, we can ignore it): \begin{align*} &\ce{Na+ + e- <=> Na} & &E°=-2.71\ \mathrm{V}\\ &\ce{2H+ + 2e- &...

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