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 do they use graphite electrodes in the Hall–Héroult process?

In the Hall–Héroult process of extracting aluminium from aluminium oxide, the electrolyte is a liquid mixture of cryolite $(\ce{NaAlF6})$ and aluminium oxide $(\ce{Al2O3}).$ The cathodes and the ...
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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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1answer
189 views

Electrolysis puzzle

I created an electrolysis setup to study how different electrolytes, their concentrations, and the electric current affect the "speed" of the electrolysis process. With that in mind, I built a simple ...
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Why put zinc solution in a galvanic cell?

In a galvanic cell with Cu and Zn electrodes, I was taught that each electrode is immersed in a solution containing it's own positive ions. I understand why you need copper ions, so they can gain ...
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558 views

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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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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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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How to calculate the potential via Hess's law? Is my textbook wrong about this?

Given the two reduction half-reactions for the following fuel cell, determine the standard cell potential $E^\circ_\mathrm{cell}$, $$\ce{CH4 (g) + 2 O2 (g) + 2 OH- (aq) -> CO3^2- (aq) + 3 H2O}.$$ ...
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If the ferric ion is more stable than the ferrous ion, then why is it readily reduced to the latter?

The standard reduction potential value for the Ferric ion: \begin{align} \ce{Fe^3+ + e- &<=> Fe^2+} & E^\circ &= 0.77 \end{align} The value is positive, hence it means that ferric ...
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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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Why can we disregard stoichiometric coefficients when computing reduction potentials?

A $\ce{Cr(s) | Cr^3+ || Cd^2+ | Cd(s)}$ galvanic cell has redox half reactions: $$ \begin{align} \ce{Cd^2+ + 2e- &-> Cd(s)} &\quad E^\circ &= \pu{-0.4 V}\tag{R1}\\ \ce{Cr^3+ + 3e- &-...
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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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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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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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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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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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441 views

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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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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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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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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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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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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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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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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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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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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Delta G for Standard Hydrogen Electrode reaction

I’m dealing with electrochemistry problems. For the following reaction $$\ce{2H+ +2e- <=>H2}\quad E^\circ=0\ \mathrm{V}$$ Does it make sense to say $$\Delta G^\circ=-nFE^\circ=0$$ Which would ...
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Electrolysis of molten nitrates, sulphates and carbonates

We know that nitrates, sulfates and carbonates doesn't or hardly oxidized by anode in the ...
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How to find the band gap for a compound?

I have processed a si/polymer hybrid using a silane coupling agent which I need to determine the energy gap / band gap. Would you please let me know the procedure to go about determining the band gap?...
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How can I produce hydrogen gas efficiently and cheaply?

I have been intrigued by one of the principles of chemistry lately- electrolysis. In my knowledge, electrolysis is a quite dangerous operation as the decomposition of water produces hydrogen and ...
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Correct equation for Ionic Conductivity (λ) in Solutions?

We haven't started on Electrochemistry at school yet, but I did manage to find some time to read up on the topic. One thing I've noticed from when I started, is that different books and sites use ...
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Why is the reaction between potassium permanganate and hydrogen peroxide spontaneous?

When hydrogen peroxide is mixed with potassium permanganate, oxygen gas and water vapour are formed, according to the reaction (source): $$\ce{2MnO4- + 3H2O2 -> 2MnO2 + 2H2O + 3O2 + 2OH-}$$ This ...
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Will nitrate be able to oxidise mercury?

We have the following data: \begin{align} \ce{NO3- + 3 e- &-> NO} &\quad E^\circ_1 &= \pu{0.96 V}\\ \ce{Hg^2+ + 2 e- &-> Hg} &\quad E^\circ_2 &= \pu{0.86 V} \end{align} ...
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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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How to determine the potential of a cadmium zinc cell under standard conditions?

I write the half-equations: \begin{align} \ce{Zn &<=> Zn^2+ + 2e^-}& E^\circ &= +0.763~\pu{V}\\ \ce{Cd^2+ + 2e- &<=> Cd}& E^\circ &= +0.403~\pu{V} \end{align} In ...
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Lemon Battery works on water?

My son and I were using a mini science experiment kit for creating batteries with copper, zinc, and lemonade, similar to the famous lemon battery project. My son's hypothesis was that the liquid had ...
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555 views

The spontaneity of a redox reaction

Suppose we have a redox reaction and we want to see in what direction the reaction is spontaneous. We do this by comparing the standard reduction potentials of the sub-reactions available in the main ...
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Electrolytic refining of copper

In refining copper, an aqueous solution of copper(II) sulphate is electrolyzed, using impure copper as the anode and pure copper as the cathode. At the anode, metal impurities higher than copper in ...
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Will oxidation/reduction of copper still occur in an electrochemical cell if it is not in an aqueous environment?

Notation of the reduction and oxidation of copper typically includes the aqueous state. Illustrated below: $$\ce{Cu(s) -> Cu^2+(aq) + 2e-}$$ This event usually occurs at 0.34 V. What if the copper ...
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Galvanic cell involving a hydrogen electrode and copper electrode in sodium hydroxide

A galvanic cell consists of a standard hydrogen electrode and a copper electrode. Suppose that the copper electrode is immersed in a solution that is $0.100\ \mathrm{M}$ in $\ce{NaOH}$ and that ...
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Formation of species in electrolysis

I understand the principles of electrolysis of salts in aqueous solutions, but there are two points on which i am unsure. At the positive electrode, how can you work out which ions will ...
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Why can some redox half-reactions be combined and some cannot? [duplicate]

I mean by "combining" is to make a new half-reaction equation and not an overall equation for a reaction in whole. For instance, I was trying to arrive at the following half-reaction: $\ce{MnO2(s) + ...
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1answer
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In a galvanic cell, why does an electrode with a higher potential “pull” the electrons from the electrode with a lower potential?

I'm doing Grade 12 Chemistry and I'm unsure of this, taking the hydrogen electorde as having a potential of 0 volts. I'll use the copper-zinc cell as an example. Just let me know if I've got the full ...
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Express the maximum work from a voltaic cell

The net cell reaction of an electrochemical cell and its standard potential is given below: $$\ce{ Mg + 2Ag+ ->Mg^{2+} + 2Ag} \ \ \ \ \ \ \ \ E^\circ=3.17\:\mathrm{V}$$ The question is to find the ...
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Electrolytic Refining of Silver Nitrate

I read that the electrolytic refining of Silver is done using dilute silver nitrate as an electrolyte and a small percentage of free $\ce{HNO3}$. The following reactions are possible at the anode: $$\...

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