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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3answers
5k views

Difference between intercalated lithium and metallic lithium (Li-ion batteries)

I have a question about Li-ion batteries. I sometimes see the two terms - intercalated lithium and metallic lithium - used when talking about this type of batteries and I was wondering what is the ...
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2answers
29k views

Why does temperature affect cell potential?

The Nernst equation describes the relationship between cell potential and temperature. But why does temperature affect cell potential? My understanding is that the collision model of kinetics is not ...
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649 views

Why do acids favor the oxidizer? And bases the reducer?

Simply put, why does adding acid to the cathode up the cell voltage? From what I understand, acids are proton donors. Do these positive protons attract electrons toward the cathode compartment of the ...
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2answers
200 views

How to separate a 5 atom thick layer of Cu from Au

I've become very curious about (electrochemical) atomic layer deposition (ALD) via surface limited redox replacement. Since the technique allows for deposition of metals in atom thick layers it's ...
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6k views

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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Why does decreasing the distance between the electrodes in an electrolytic cell increase the rate of electroplating?

I did an experiment on the effect of the distance between the electrodes on the rate of electroplating in an electrolytic cell (copper electrodes with copper sulfate electrolyte). As I expected, when ...
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15k views

Derivation of relationship between Gibbs free energy and electrochemical cell potential

Why is $\Delta G = -nFE$? I don't understand what the motivation is behind this definition. Was it derived or just given? The textbook provides no justification for this equation. In fact, much of ...
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1answer
8k 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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12k 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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1answer
377 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 ...
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1answer
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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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2answers
16k 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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1answer
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 ...
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1answer
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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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1answer
446 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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1answer
688 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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9k 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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2answers
429 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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Ratios of produced gases in water electrolysis

I just did a little water electrolysis experiment at home by immerging two aluminum electrodes in water with a small amount of table salt. The voltage of the battery was 6 V. What surprised me is ...
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1answer
255 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 ...
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1answer
194 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. ...
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1answer
295 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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1answer
4k 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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709 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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2answers
3k 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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1answer
6k 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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4answers
890 views

How can a neutral atom attract electrons when it's supposed to have zero charge?

A neutral atom is an atom with an equal number of protons and electrons We know the force of attraction between the proton and electron is equal and assuming that: one proton's positive charge ...
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2answers
634 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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11k 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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576 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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1answer
2k 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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2answers
7k 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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317 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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What is the procedure of designing a salt bridge for a galvanic cell?

I'm doing an experiment where I'm measuring the effect of changing the $\ce{Cu^{2+}}$ ion concentration on the voltage in a copper-zinc galvanic cell. I'll be doing at least five trials for each of ...
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1answer
393 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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1answer
1k views

What determines the electronegativity of an element?

Is it possible to work out without post-Bohrian mathematics?
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24k 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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720 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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1answer
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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9k 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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1answer
37k views

What determines the strength of reducing and oxidizing agents?

The best reducing agents are located at the bottom left of the periodic table (low electronegativity) and the best oxidizing agents are located at the top right of the periodic table (high ...
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1answer
1k 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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1answer
922 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
385 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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0answers
176 views

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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485 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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2answers
1k 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
13k views

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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3answers
23k 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
409 views

What is the optimal voltage for storing a 3.7 V lithium polymer battery?

According to this website, storing a lithium polymer (LiPo) battery/cell at around 40% capacity would be more beneficial for the lifespan of the LiPo cell comparing storing the battery at 100% ...

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