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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199 views

Does a zinc metal coating react with coffee in a coffee grinder?

I'm restoring an old coffee grinder and I want to give the grinder mechanism a nice zinc / silver coating. But I read it is not safe for zinc to be in contact with acidic foods. When I look at the ...
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Why do positive ions go to the cathode?

In electrolysis why do positive ions go to the cathode? Since the cathode is positive, won't the positive ions face repulsion at the cathode and would require more energy? I understand that reduction ...
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Does concentration of salt increase or decrease rate of rusting?

I want to know whether increasing the concentration of salt, specifically $\ce{NaCl}$, increases or decreases the rate of rusting. There are conflicting theories that explain opposite outcomes: ...
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4k views

What visual observations can confirm that a reactant is the limiting reagent?

I have this lab question for the lab called Copper Collection Stoichiometry, where we choose an amount of the limiting reagent (iron) for a reaction between copper (II) sulfate and iron. We are to ...
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11k views

Does potential difference or current drive electrolysis?

Would a high voltage ( of the order of a few score kV ) drive electrolysis? Or, does it require a large current and low voltage? Alternatively, does electrolysis require both large voltage & ...
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372 views

Is this product description wrong and a simple battery and not a fuel cell?

I won this "toy" at a science fair... Now I have to make a short presentation about it in school. On the package description they describe its energy source as "fuel cell"... It consists out of a ...
8
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1answer
853 views

Green color substance forming during electrolysis

A green-colored substance formed during electrolysis, wherein the electrolyte was magnesium sulfate and minerals in tap water. I did not have any leads to stick into the water, so I just put a 9 ...
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6k views

Relationship between surface area of electrode and reaction rate of hydrogen in fuel cells

I am looking at the effects of increasing the surface area of which the flowing hydrogen fuel is in contact with the anode in a fuel cell. At the anode the hydrogen is catalytically split into ...
8
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371 views

Scary jelly forming on zinc anodes

I'm continuing with my electrolysis experiments. Over a long time, I seek a perfect electrodes. It seems, that when you pick the right anode and cathode, it might be a lot cheaper than universal super-...
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397 views

How do I determine whether it is the *ferrous* or *ferric* ion that is implied in this displacement reaction?

I'm supposed to write a balanced equation for: $$\ce{Iron(s) + copper(II) sulfate(aq) -> ?}$$ If I use Iron(II)/ferrous I get $$\ce{Fe + CuSO4 -> FeSO4 + Cu}$$ and if I use Iron(III)/ferric, ...
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7k views

Identity of a green substance formed during electrolysis reaction?

I did a short experiment in which I connected a $1.5\:\mathrm{V}$ battery with 2 paper clips into a bowl of water to which I added salt. After a while, I saw a yellowish-greenish cloud inside the ...
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198 views

What is the precise definition of maximum work in the context of electrochemistry and thermodynamics?

I'd like clarification of the meaning of $W_\text{max}$ in the following equations (and thus in the combined result in the third equation): \begin{align} W_\text{max} &= \Delta G\\ W_\text{max} &...
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242 views

Can I use one alkaline battery to recharge another?

Unfortunately, I don't have batteries to waste to test this myself, but I am curious... Let's say you have two identical batteries. AA Duracell. Now let's say you run one of the batteries through ...
8
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1answer
165 views

Fundamentals of Li-ion Functionality

I would like to have an in-depth understanding of Li-ion batteries functionality, at atomic level. Can anyone help me to understand it? I have included some known background to support my questions. ...
8
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1answer
255 views

Difference between non-thermal and thermal ionized gases

Why or when does non-thermal plasma become thermal? How do we know before hand if the ion temperature will differ from the electron temperature, on what parameters does it depend - where is the ...
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646 views

Lithium batteries a reality - why not sodium, pottasium batteries?

Lithium batteries seem to be mainstream now, offering high energy density, high output current capability. Stepping down the periodic table there are alkali metals with greater electronegativity than ...
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1answer
3k views

Can lead-acid batteries release CO? Or can a CO sensor detect gasses other than CO?

I recently found myself troubleshooting a CO alarm on a houseboat. Inside the cabin, a Fluke CO-220 was reading 40 ppm. In the generator engine compartment, the CO level was zero (while the generator ...
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1k views

Electroless Plating of Zinc onto Copper in NaOH Solution

I’m researching how the classic “alchemy” demonstration works in which zinc is plated onto a copper penny in a solution of sodium hydroxide. Most online resources refer to the electroplating of copper ...
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524 views

Create my own solar cells?

How would I grow my own and build functional solar cells? I've read and researched that they're mostly a crystal structure of something like silicon. I would assume I'd be able to grow my own crystals ...
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192 views

Still taught to reverse oxidation half cells in electrochemistry?

In a question, Oxidation of metals/halogens by oxygen gas in acidic aqueous solution, there was a point made that reduction half-cells should not be reversed. I was taught ($\approx 1970$) in the ...
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12k views

How to determine the value for n in the Gibbs free energy and redox potential equation?

I am having a problem with this equation for redox potentials $$\Delta G = -nFE_\mathrm{cell}$$ In this equation I never am totally sure about what the value of $n$ should be, for example for the ...
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299 views

Prediction of ionic reduction?

Here are some standard electrode potentials:- $$\ce{SO_4^{2-} + 4H^+ + 2e^- -> SO_2 + 2H_2O}\\E^o=0.17\mathrm{V}\\ \ce{NO_3^- + 4H^+ + 3e^- -> NO + 2H_2O}\\E^o=0.97\mathrm{V}\\ \ce{NO_3^- + ...
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1k views

What determines the electronegativity of an element?

Is it possible to work out without post-Bohrian mathematics?
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319 views

Is there a better equation than the Nernst equation for low concentrations?

The Nernst equation can be applied to the whole cell reaction or a half-cell reaction. Consider the half cell reaction: $$\ce{Cu^{2+} + 2e^- -> Cu(s) \quad \quad E^0 = +0.337~\rm{V}}$$ The Nernst ...
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3k views

Why can't a galvanic cell be a single cell?

I get that galvanic cells require a salt bridge to maintain neutrality so the cathode doesn't become saturated with electrons, but why is a two-cell setup required? Wouldn't the spontaneous reaction ...
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628 views

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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2k views

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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8k views

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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978 views

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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256 views

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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4answers
325 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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2answers
840 views

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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1answer
441 views

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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1answer
3k views

Why does the Co³⁺/Co²⁺ couple have such a high reduction potential?

Cobalt is changing from $\mathrm{(3d)^6}$ to $\mathrm{(3d)^7}$ electronic configuration. What's so stabilizing about that? Just by reduction potentials this couple is more oxidising than hydrogen ...
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2k views

Why exactly are standard potentials additive?

I don't really study chemistry so while my question may be very obvious, its not obvious to me. If we take an electrochemical reaction like $$\ce{2Fe^2+ + Au^3+ -> 2Fe^3+ + Au+}$$ we can find its ...
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20k views

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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1answer
214 views

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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3k views

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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2answers
6k views

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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1k views

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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1answer
8k views

Why conductivity of electrolyte decreases on dilution, but molar conductivity increases?

I learnt that on dilution of an electrolytic solution, it's conductivity decreases. However, there is an increase in the molar conductivity of the solution. The book explained the reason by comparing ...
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1answer
19k views

Salt concentration and electrical permittivity of water

We know that the electric flux density $D$ can be related to electric field intensity $E$ as $D=\epsilon(\omega) E$ $\epsilon(\omega) = \epsilon_0 \epsilon_r(\omega) $ where $\epsilon_0$ is the ...
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1answer
4k views

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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1answer
251 views

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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1k views

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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1answer
927 views

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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3answers
18k views

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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1answer
16k views

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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234 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 ...