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 ...


7

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 the electrodes, they are not discharged. But they neutralize the charges of the ions that are produced out of water being destroyed at these electrodes. Let's ...


6

The answer is quite simple, if you look at the equation carefully. Conductance and conductivity are related by cell constant, $\displaystyle\frac{\text{Area}}{\text{Distance}},$ where the area is the area of the electrodes and the distance is the distance between the electrodes. $$G = \sigma\frac{A}{l}$$ In conductivity measurements, the cell constant was ...


6

$PV = nRT$ and $\ce{2H+ + 2e- -> H2}$ are your best friends. Step 1: Find the number of moles of hydrogen gas released Use the formula: $PV = nRT$, where $P =$ Pressure exerted by the gas, $V =$ Volume of gas, $n = $ number of moles of gas, $R = $ universal gas constant, $T = $ temperature of gas. Using this formula with $P$ in atm and $V$ in liters we ...


5

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): The solubility of gold in solid gallium can be considered to be zero. The solubility of gallium in gold is not zero, but is on the order of a few atomic percent....


4

Sometimes the electrolyte directly takes part in the chemistry, by being oxidized or reduced at an electrode. In those cases, it is easy to understand why the concentration would have an influence on the kinetics of the redox reactions (and with that, on the observed electrical current). For water electrolysis, the "active" electrolytes are ...


4

No ! It is not possible to deposit aluminum by electrolysis of a water solution. It may be done in a solution of $\ce{AlCl3}$ in an organic solvent like toluene, but not in water. And even in toluene, the conductivity is low. Metallic aluminum reacts with water, when this metal is not protected by an outer layer of aluminum oxide $\ce{Al2O3}$ as it is as ...


3

It depends on the substance you have used for your electrodes. If they are in platinum, they will not be altered. If they are in carbon (charcoal, graphite), they will not be chemically tansformed, but after a while, they will be slightly corroded, and some powder of charcoal will progressively appear under the electrode on the ground of the flask used for ...


3

If a cathode (negative pole) is placed alone in an ionic solution (without any anode in the solution), it will attract cations from the solution, and discharge maybe one or two or one thousand of these cations. This will last maybe 1 nanosecond, and then it will stop. The reason is that this number of atoms is extremely small, so small that the neutral atoms ...


3

It is good question given the fact that this idea is not commonly discussed. The main source of your confusion is the following idea Why doesn't water dominate any electrolysis reaction since even if a small percentage of the collisions of water can accomplish the reaction? The sheer number of collisions on its side will ensure it wins. Unlike chemical ...


3

As a cathode is usable near any conductor, which does not dissolve in electrolyte. Anodic material must withstand aggressive anodic oxidative processes without dissolving. Aside of platinum, glassy carbon is often used. Questionable can be stainless steel. Electrodes should not be vulnerable to desintegration by evolving gases. E.g. otherwise inert but ...


3

A good electrode for electrolysis is: An electrical conductor. Chemically stable in water and in oxydizing environment of the anode / reducing environment of the cathode. Most metals are OK being cathode in electrolysis as they fulfill both conditions. Well, sodium and friends are not good - it is not stable in water in the first place. Some non-metal ...


3

A less laborious path to very fine iron dust (in fact, likely pyrophoric iron) perhaps follows from first purchasing or preparing iron(II) oxalate (a path is detailed in a reference provided below). Next, thermally decompose the salt and finally, stabilize the nano-iron product with say mineral oil. The details on the thermal decomposition in an atmosphere ...


3

You have replicated electro-rafination of copper. Copper ions from the being dissolved anode are replacing the copper ions being deposited on the cathode. Therefore overall electroneutrality of the solution is kept. The local neutrality is managed by electromigration of both ions $\ce{Cu^2+}$ and $\ce{SO4^2+}$.


3

Original Question: Why an aqueous solution of $\ce{NaCl}$ conducts electricity Because $\ce{NaCl}$ is an electrolyte. This means it yields ions in solution. Simply put, solid $\ce{NaCl}$ consists of $\ce{Na+}$ cations and $\ce{Cl-}$ anions bound together in a rigid crystal lattice. When it melts or is dissolved in water, the crystal lattice breaks. The ions ...


3

The basic reason for using graphite as an anode is in Hall–Héroult process in the electrolytic reduction of alumina to aluminum metal is because graphite being an allotrope of carbon and an inert electrode reacts with oxygen to give out carbon dioxide which thus prevents the liberation of oxygen as a final product at the anode. Had there been any other metal ...


3

I guess the misunderstanding arises from the fact that you treat $n$ as the same entity as the lowest common multiple (LCM) used to balance the net equation using half-reactions for the electrolysis of molten aluminium(III) oxide: $$ \begin{align} &\text{cathode:} &\ce{Al^3+(melt) + 3 e- &-> Al^0(l)} &|\cdot4\tag{red}\\ &\text{anode:} &...


3

For an electrolytic cell, a galvanic cell is nothing else but a power source. For a galvanic cell, an electrolytic cell is nothing else but a powered electronic circuit. The galvanic cell anode/cathode does not form with the electrolytic cell cathode/anode a respective separate cell, as there is no ionic flow between them. Similarly for a simpler case, 2 ...


3

Reduction and oxidation are defined as gaining and donating electrons from the valence shell of an atom respectively. Whereas in the case of electrons flowing in the electrodes and connecting wires the electrons are passing from the interatomic voids and not being released by the wires and the electrode. (There will be some electrons which will interact with ...


3

The answer is no. If an electric current is flowing through a piece of metal (platinum or anything else) than the same number of electrons are getting in and getting out of the piece at either ends of the piece. No atoms are reduced or oxidized. The total number of electrons present in the metallic piece does not change. There is no oxidation and no ...


3

Well I'm not completely sure but I'll try to answer. To answer your first question, yes, it is almost always certain that the half reaction with the greater $E^\circ$ will determine the correct combination. But, as always there are instances when the above is not always true due to reaction factors. For instance, in the electrolysis of a $\ce{NaCl}$ solution,...


3

An electrolyte (in your case water) keeps charge carriers (in your case $\ce{Na+}$ and $\ce{Cl-}$) separate from each other and allows them to travel to the electrodes. There is no constraint that this has to be a liquid phase, or a solid (e.g., a polymer). I speculate when you say «In electrolysis of water the water is consumed not the electrolyte.» you ...


2

The mental conflict occurs because two processes could theoretically happen (electrodeposition of sodium, or electrodeposition of hydrogen), and the theoretically unfavorable one occurs - and not only occurs, but is so favorable that it was used commercially to produce NaOH as EdV noted. So why is the theoretically favored process not favored in this ...


2

Small and/or highly charged ions tend to be highly solvated in water. These solvated ions may still be smaller than the solvated ions of larger ions. However, water molecules are not as free as the molecules of a gas. Water has a much higher viscosity, for instance. So think of water as a loose gel. A large (unsolvated, or poorly solvated) ion has an easier ...


2

There is a rather interesting explanation as to why only sodium ion can pass through a cation exchange membrane and chloride ion is repelled by it. Let us recall some properties a) Ion exchangers are very good electrical conductors. This is well studied in the 1940s. The current is carried, not by electrons but by mobile ions in ion exchange resins. In a ...


2

With decreasing electrolyte concentration, either the needed voltage raises at constant current, either the passing current decreases at the constant voltage. Both happens because at lower concentration, a higher potential gradient across the electrolyte is needed to maintain the same current, as the smaller ion count requires ions to move faster for the ...


2

Lithium has a standard redox potential equal to -$3.04$ V. Coupled with any compound at the cathode, it could hardly produce cells yielding more than $4$ Volts, because part of the available energy is needed and lost to extract the external electron of the Lithium atom. The performance of a cell built with a Lithium anode could be more important if the ...


2

Mentioned deposition of metallic magnesium or aluminium does not work, unless it is molten salt, or there is a mercury cathode. Opposite potentials are for the mutually opposite half reactions. Water oxidation and water reduction are not the opposite half reactions. Oxidation of $\ce{H2O}$ to $\ce{O2}$ is not the opposite to reduction of $\ce{H2O}$ to $\ce{...


2

Some electrolysis experimets are best first performed and then an attempt at explanation. For example, the products of the electrolysis of aqueous nickel nitrate with graphite electrodes are reportedly per a source (with video) as: Electrolysis of a nickel nitrate solution produces oxygen at the anode, and hydrogen and nickel at the cathode. Looking at ...


2

My question is this: Does electrolysis work the same way when the cathode and anode are made of the same metal? It might be a stupid question, but I can't find anything that answers this question specifically. The battery or the power source does not care about the electrode material. Its job is to pump the electrons in the circuit. Now the problems ...


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