Questions tagged [electrochemistry]

The branch of chemistry that deals with the study of redox reactions and how they can be applied to generate electricity (in electrochemical cells) and to carry out non-spontaneous reactions using electricity (electrolysis).

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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 ...
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How does a reference electrode work in a three electrode system?

This is what I understand about three electrode electrochemistry (correct me if I am wrong): The working electrode is where the reaction of interest happens, e.g. copper ions reduced to solid copper. ...
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galvanic corrosion in the wild: where is the reduction?

Galvanic corrosion occurs of an active metal (i.e. iron or zinc) in contact with a passive metal (i.e. copper) in a conductive solution. A famous example is the corrosion of iron girders in contact ...
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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!
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Why is the cyclic voltammetry of my ferrocene compound not showing a standard shape?

I am trying to set-up a new cyclic voltammetry measurement station in my lab but the results are very poor. I am using the following parameters: ...
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1 answer
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How are the chemical reactions of the table of standard reduction potentials experimentally determined?

My background: I've read several books and articles on electrochemistry and even do photoelectrochemical research in a lab, so I'm somewhat familiar with the concepts and techniques. In texts on ...
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Activity Coefficients from Electrode Potentials

Lets say we want the activity coefficient of $\ce{Cu^{2+}}$ ions in solution. Would we simply setup one half cell of a $\ce{Cu}$ electrode in a known concentration of $\ce{CuSO4}$ and then connect ...
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Why can primary cells not be recharged effectively?

Primary cells cannot be recharged effectively because their reaction products are not in contact with the electrodes. True or false? I got it correct just by rote-learning the theory so the answer is ...
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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 ...
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7 votes
4 answers
388 views

Varying potential diffrence between two graphite strips in NaCl solution

I have two identical graphite strips of dimensions 3.5 cm by 1 cm. Both are 3/4 submerged in aqueous $\ce{NaCl}$ solution (0.34 mol/dm$^3$, 2% wt) separated by a distance of 7 cm. I have attached ...
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What exactly is an "electron-sponge"?

What exactly an "electron-sponge" [behavior/action/property/system] nickname is, and what makes a material an "electron-sponge" (preferably, quantitatively)? From what I found, it's typically a ...
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The open circuit voltage of a battery: Does it decrease with increase in pH of electrolyte while the voltage across a load increase?

Why does the open circuit voltage of a battery decrease with increase in $\mathrm{pH}$ of electrolyte, but the voltage across a load increase? I tested a cell which had aluminum sulfate as its anode ...
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Does phosphoric acid remove stainless steel electropolished layer?

Electropolished stainless steel has a high corrosion resistance due to the oxide film that is created during electropolishing. The film mainly consist of chromium(III) oxide. Phosphoric acid is ...
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2 answers
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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 ...
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Electronegativity of zinc vs copper in galvanic cell

I am reading up on how galvanic cell works and I realised that the flow of electrons is from Zn to Cu. But Zn is more electronegative compared to Cu according to periodic table trends I read it ...
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1 answer
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Can gas be made to block radiation better?

Can any gas block radiation? I ask this because I would like to know if the properties of any gas element would chemically react differently with radiation from adding an electrical current. This ...
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Why do Electrons leave the Zinc in a Galvanic Cell

What induces electrons to leave the atoms around the part of the zinc metal in a solution to travel up along that zinc metal and above the solution, through the wire and to the copper metal and ...
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Magnesium air-fuel cell or battery?

I'm a bit confused. I've got this "toy" ... with the help of this site I was abled to find out that the reaction stops with a lack of air. Link to the old question. The battery/fuel cell or however ...
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Meaning of electrochemical cell notation without a salt bridge

An electrochemical cell is shown here. $$\ce{Ag(s)~|~AgCl(s)~|~KCl(1M)~|~Hg2Cl2(s)~|~Hg(l)~|~Pt}$$ I am used to seeing cell representations with a $||$ for a salt bridge between the two electrode ...
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Would an amalgam filling under or next to a gold crown cause any electrochemical reaction?

Would a mercury amalgam filling deteriorate faster if it was in contact with a gold crown?
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Why does a complete discharge destroy a Li-Ion-Battery?

I read that completely discharging a Lithium Ion Battery is a very bad idea because it will lose plenty of capacity. But why? I know that the reaction (fot the LiFePO4 battery) is: $$ \ce{LiFePO4 + ...
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Will magnesium undergo a redox reaction with zinc(II) or copper(II)?

Magnesium can do a redox reaction with $\ce{Cu^2+}$ as well as with $\ce{Zn^2+}$, since Mg has the lowest reduction potential $E_0$. (I am aware that a reaction may or may not be feasible as redox, ...
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2 answers
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Butler-Volmer equation with concentration dependence?

For a simple elementary reaction on electrode \begin{equation} O+e^-\rightleftharpoons R \end{equation} We can derive the Butler-Volmer equation. But it seems that the formula found on John Newman's ...
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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 ...
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Salt concentration and electrical permittivity of water

We know that the electric flux density $D$ can be related to electric field intensity $E$ as $$D = \epsilon(\omega) E$$ where $$\epsilon(\omega) = \epsilon_0 \epsilon_r(\omega)$$ and $\epsilon_0$ ...
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Side products during the electrolysis of Copper Sulfate?

Using good quality reagents, during the electrolysis of $\ce{CuSO4}$ (at $\mathrm{15V ~ \& ~ 2A}$), I have noticed a significant amount of Hydrogen generated at the negative electrode in addition ...
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AgI and AgCl reduction potentials

The reduction potential for $\ce{AgI}$ is $-0.15\ \mathrm{V}$ and for $\ce{AgCl}$ it’s $0.22\ \mathrm{V}$. As $nFE =-\Delta{G} = T\Delta{S} - \Delta{H}$ this must imply that $\ce{AgI}$ is a stronger ...
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How exactly does electrolysis occur if the molar conductivities of cation and anion are different?

I'm having trouble wrapping my head around Kohlrausch law of infinite dilution and molar conductivities in general. For a salt $\ce{AB}$ the molar conductivity at infinite dilution can be expressed as ...
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6 votes
2 answers
148 views

Is pH in a charged hydrogel and its supernatant solution constant?

Let us assume we deal with ideal systems without interactions. The gel phase and the supernatant solution phase are in thermodynamic equilibrium. The supernatant solution shall consist of different ...
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1 answer
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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 ...
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Does water vapor in the air oxidize copper?

My friend is installing copper pipes in his house, which is going to be in a humid area, and he says that copper will only be oxidized by the air and the excess water vapor in the humid air won't ...
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1 answer
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Why is the water reduction of oxygen favored in acidic conditions?

The standard reduction potential of diatomic oxygen in acidic conditions is +1.23 volts. However, the standard reduction potential of diatomic oxygen in basic conditions is only +0.40 volts. Why is ...
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6 votes
1 answer
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What is an efficient way to generate CO2 electrochemically?

I would like to build a small carbon dioxide generator for experimental purposes. There are two requirements that are set in stone: It has to be electrochemical. (Easy to switch on/off with ...
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6 votes
1 answer
944 views

Why does the specific conductivity against concentration curve for NaCl curve more than KCl?

I understand why KCl has a higher specific conductivity than NaCl.. but I dont understand why the curvature is more significant for NaCl (KCl is a straight line). Ive provided a picture of this here, ...
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Protons and osmotic potential

In a hypothetical enclosed membrane only permeable to water (including hydronium), where inside the pH is lower than the outside, would water move inside?
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6 votes
2 answers
432 views

Will a film of oil on water retard evaporation (of water) and prevent air and atmospheric impurities from diffusing into it?

I vaguely recall hearing that a layer of oil on water will slow down the evaporation of water, as well as serving as a barrier that would prevent (or retard) the diffusion of air and atmospheric ...
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6 votes
1 answer
1k views

Does conductivity change in a solution due to rust?

I plan on conducting an experiment in which I place an iron nail in water and analyze its rate of corrosion into rust with different concentrations of NaCl. My original plan was to cover the water in ...
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6 votes
2 answers
11k 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 ...
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6 votes
1 answer
2k views

Corrosion of a galvanic couple made with silver and gold

If a bangle is made out of gold and silver, connected with each-other would there be corrosion happening? If so, can it be explained using the galvanic series? Also do those metals undergo oxidation ...
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1 answer
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Is possible to figure out if a battery is NiCd or NiMH?

Aside from opening it of course. I'm not sure if this is the right place to ask this but I have a rechargeable battery pack for an Xbox One controller and the info on it says that it's a sealed nickel ...
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6 votes
2 answers
1k 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 ...
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What is the role of hydrochloric acid in a copper electroplating bath?

Considering water as a given, the third most important ingredient in a copper electroplating solution, as a short survey of related recipe webpages will show you, is hydrochloric acid (HCl). Here's a ...
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6 votes
1 answer
1k views

Clarifications on thermodynamic cell efficiency

The thermodynamic efficiency of any cell (especially Fuel cells) is given as $$\frac{\Delta G}{\Delta H} \times 100$$ I understood this partly, that since $\Delta G$ is the useful work obtained in ...
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Correct Definition of Absolute Electrode Potential

I thought absolute electrode potential is Galvani potential difference at the interface. However, it is given by following equation in John Bockris - Modern Electrochemistry (Ref.1): $$ E^M \mathrm{(...
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Removal of nickel plating on MgB2 without damaging the boride?

I need to remove a nickel plating of a MgB2 wire without causing damage to the MgB2. I felt that electrolysis is the best method but I do not know what electrolyte to use for this. I also need to coat ...
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2 answers
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Is there a potentiometric method for monitoring salt formation in organic solvent?

I work in a pharmaceutical R+D lab, and currently aim to develop a validatable potentiometric method for determining the optimal amount of acid to add to a basified small organic molecule for ...
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2 answers
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How to measure chlorine content using ORP sensor?

In my project I need to measure pH, turbidity, and chlorine level of treated drinking water. I found sensors for measuring pH, turbidity, and also chlorine. The actual problem begins is that the cost ...
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5 votes
5 answers
3k views

Electrolysis of Water

What is the mechanism for the electrolysis of water? I understand that hydrogen and oxygen gas are made, but how exactly does this happen when electrons are passed through water? A diagram would be ...
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5 votes
4 answers
785 views

Explanation for a basic decomposition of water experiment

My son is trying to write a conclusion for a basic decomposition of water experiment using a 9 V battery (with a test tube placed over each terminal) placed inside a salt water solution. The results ...
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5 votes
2 answers
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Copper layer doesn't stick after Copper electroplating

I am playing around with copper plating using Copper Sulfate solution with electricity. I am using 2-2.5 volts as power source and around 100-500 mA. It is actually a very small container around 100 ...
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