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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2k views

Why are potentials of cells with magnesium electrode always lower than expected?

I have prepared the 1M water solution of magnesium acetate. Then I placed $\ce{Mg}$ and $\ce{Cu}$ electrodes in it. I predict there such reactions take place: $$\ce{Mg-2e^- \rightarrow Mg^{2+}}$$ $$\...
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363 views

Ion-selective electrodes

Some ion-selective electrodes can be expensive (starting from $500). Is there any relatively inexpensive do-it-yourself alternatives that would still give very accurate results? How does one make an ...
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How do I derive the Nernst equation in the case in which R is absent?

Does anyone know what the intermediate calculations are to obtain equation 1.4.14? Taken from Fundamentals and Applications (Bard) page 31 To be more precise, how to obtain (1.4.14) from $\frac{...
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880 views

Variable oxidation state of transition metal ions

Transition metals can form stable ions with different oxidation states. But I am confused why doesn't only the most stable state exist. Let me clarify my question more: $$\ce{Ti^{2+} -> Ti^{3+} + ...
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577 views

Voltage vs current density - why are both parameters important to control an electrochemical reaction?

In many electrochemistry scholarly articles/studies they talk about certain specific reactions occurring at certain voltage potentials, while in other articles they talk about current density as the ...
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189 views

Thought Experiment: Applying a high frequency high voltage to methane

I am in the process of constructing a kitchen waste digester (vegetable/fruits) from which, hopefully, over time adequate methane may be collected to burn. The digester won't be complete for several ...
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208 views

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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176 views

Galvanic cells/redox - confused regarding diagram

I'm not sure if I got this wrong because I interpreted the cell incorrectly. When they have an arrow pointing in to the tube for $\ce{O2}$, does this imply that $\ce{O2}$ is a reactant? If so then B ...
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130 views

What is the reason of explosion of batteries?

In social sites we see many pictures showing awareness of not using smartphone while charging because of the reason that battery explode while charging, is really batteries explode and if yes than ...
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1k views

In a galvanic cell where the two electrodes are in the same electrolyte solution, why do reduction and oxidation occur separately?

In a certain book, I was presented with the following solution: An iron nail is attached by a piece of wire to a magnesium ribbon, and the iron and magnesium are placed into the same container, with ...
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Calculating Fluoride in toothpaste

Question A linear regression line was obtained; $$\log(\ce{[NaF]})~(\mathrm{mol~L^{-1}})~ \mathrm{vs~EMF}: y = 59.8x +600.8$$ $0.7540~\mathrm{g}$ of toothpaste was diluted in a$50~\mathrm{mL}$ and ...
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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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408 views

Hydrogen electrode

Why the hydrogen gas should be bubbled continuously through the electrolyte in a hydrogen electrode? To keep the solution saturated with hydrogen gas To clear the platinum electrode To ...
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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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Ca and Mg hydrated radius in clay flocculation

Ca has an atomic radius of $197\mathrm{~pm}$ and a Pauling electronegativity of $1.00$. Mg has an atomic radius of $197\mathrm{~pm}$ and a Pauling electronegativity of $1.31$. Since Mg is smaller ...
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Calculating ideal chemical work using extent of reaction and chemical potential

I have a electrochemical reactor assumed isothermal and isobaric with 4 reactions and I am trying to calculate the "ideal chemical work' exerted by each reaction using the extent of reactions for each ...
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432 views

What are the factors that affect the redox reactions?

In my work, I used $\ce{Co(OH)2}$ and $\ce{Ni(OH)2}$ as an active materials to fabricate as symmetric supercapacitors in which I used 1-butyl-1-methylpyrrolidinium dicyanamide as an electrolyte. From ...
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Thought Experiment: Is it possible to preserve the charge imbalance present during molten lead(II) bromide electrolysis?

Suppose I were to electrolyse some molten lead(II) bromide. According to what I have been taught, the lead ions travel towards the cathode and are reduced at it, while the bromide ions are oxidised at ...
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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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254 views

Reduction of vanadyl ion

I want to reduce vanadyl to vanadium (III), can somebody please suggest some appropriate methods for it? I am trying to make a redox flow battery for a project but I have only vanadyl sulfate.
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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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5k views

Is there always a need for a salt bridge to let a galvanic cell work continuously?

I read in a book that "Sometimes, both the electrodes dip in the same electrolyte solution & in such cases we do not require a salt bridge". How is this possible?
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How come ∆G ≤ 0 is used for spontaneity in electrochemistry, not ∆G ≤ W(other)?

The spontaneity condition for a system at constant temperature and pressure in which the only type of work accomplished is of the $pV$ type can be expressed as: $$\Delta G\le0\tag1$$ In case of ...
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Can the thermodynamic predictions of redox reactions based on E and dG contradict each other?

I am referring to the following three reactions. Two of these reactions are imaginary ($\ce{M}$ and $\ce{X}$ are imaginary). $$\begin{alignat}{3} \ce{X- + 2e- \;&<=> X^3-} \qquad &&...
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Determination of solubility equilibrium using galvanic cell reactions

This is the problem: We can determine the solubility equilibrium for silver bromide using cell: Ag (s) | AgNO3 (aq) || KBr (aq) | AgBr (s) | Ag (s) We know that: $\text{AgBr} + \text{e}^- \...
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Could a lead-acid battery electrolyte be replaced by hydrochloric or nitric acid?

Hydrochloric acid, as well as nitric acid, are also strong acids like sulfuric acid. So, why are not they used commercially in lead-acid batteries?
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What is the difference between molar conductance and molar conductivity?

I'm learning (or at least trying to learn) about electrochemistry, but a major obstacle to that, is that different books I refer use different terms for the same symbols. So in a last ditch attempt to ...
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420 views

Reduce chlorine gas

I have a simple electrolysis setup which uses aqueous sodium chloride as electrolyte. The problem is that, the setup makes tons of chlorine gas along with hydrogen (I only want hydrogen). I didn't ...
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Explanation for the reactions in a saltwater battery with zinc and copper electrodes

I am a physicist, not a chemist. I'm trying to get a basic understanding of the reactions taking place in a battery using a saltwater electrolyte with copper and zinc terminals. I'm writing a general ...
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Why is zinc deposited on copper when boiling an aqueous zinc sulfate solution?

I did an experiment where I dissolved 30 grams of zinc sulfate in water and boiled it with strips of solid zinc metal and strips of copper metal and a layer of zinc was deposited on the copper. I ...
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No sign flipping while figuring out the emf of voltaic cell?

I learnt that for a voltaic cell, the value for the $E_\text{cell}^\circ$ when the reaction is spontaneous is given by $$E_\text{cell}^\circ = E_\text{cathode}^\circ - E_\text{anode}^\circ, \label{...
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Is water acidic enough for an redox reaction involving H+?

If you stored $\ce{Pb(NO3)2(aq)}$ in a $\ce{Cu(s)}$ container, would any reaction occur? Lead(II) ions will not react spontaneously with the copper solid as the $E^0_\mathrm{net}$ of the reaction ...
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Cheap metal to replace platinum in hydrogen fuel cell

Platinum is used as a catalyst in hydrogen fuel cells because it increases the efficiency. However, if I just want to make a fuel cell for demonstration purposes, I don't want to use a lot of money to ...
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Why does the copper anode dissolve?

In such a setup, the copper anode is known to dissolve. My question is, why? Does it not receive electrons from the $ \ce{OH^-}$ ions. And if you say that those electrons just flow to the battery, let ...
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Reaction of an electrode

Why is the cathodic reaction of $I^-/AgI/Ag$ is $$\ce{AgI + e- -> Ag + I-}$$ but not, $$\ce{Ag+ + e- -> Ag }$$ whereas, in $Ag/AgCl(s)$, $KCl$(0.2M); it is $$\ce{Ag+ + e- -> Ag}$$
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Extraction of hydrogen and oxygen from water

The apparatus that I am using is a glass container, with two electrodes,two glass cylinders, water, and a battery. In the glass container will be filled with water and two electrodes kept inside the ...
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51 views

Is the Standard hydrogen electrode potential at T other than 298 K also zero?

The standard hydrogen electrode potential by conventional at 298 K is taken to be 0.00 volts. This is what I have been taught. It talks about SHE at 298 K, so is the hydrogen electrode potential at a ...
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203 views

Electrolysis of water: Which equations to use? (IB Chem)

There is a list of standard electrode potentials at 298 K from the p. 23 of IB Data Booklet 2016. Which of the following equations (forward/backward reactions), from the two possible ones involving ...
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Why is mass gained at the cathode?

I'm dealing with a voltaic cell constructed like this: (From “Electrochemistry”, chapter 19 from the book Principles of General Chemistry (v. 1.0).) I understand that as oxidation occurs at the $\...
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135 views

How could a rechargeable battery recharge itself?

I'm an engineering student preparing for my graduation, in one step of my graduation project I used a rechargeable battery(1.2 volt), i was shocked when this battery is starting to recharge it self ...
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756 views

How do I setup the electrodes for cyclic voltammetry on a capacitor made on dry copper sheets?

I'm trying to measure capacitance of a cell I'm creating. It's composed of two copper-sheets with nano-material coated on one side, sandwiched with a membrane and wetted with $\ce{KOH}$. All of the ...
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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 many electrons are transferred in this redox reaction?

I have the following reaction: $$\ce{CH_4 (g) + 2O_2 (g) \rightarrow CO_2 (g) + 2H_2 O(l)}$$ How do I determine how many electrons are transferred in this reaction? More specifically, I need to know ...
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Finding EMF of a galvanic cell without standard potentials

For the galvanic cell $$\ce{Ag | AgCl(s), KCl (\pu{0.2 M}) || KBr (\pu{0.001 M}), AgBr(s) | Ag}$$ find the EMF generated given $K_\mathrm{sp}(\ce{AgCl}) = \pu{2.8e-10},$ $K_\mathrm{sp}(\ce{...
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How does equalizing voltage for lead acid battery depend on the temperature?

I am using advanced lead-carbon batteries (these ones) in an off-grid solar system. The spec specifies equalizing voltage 14.1 V for 12 V block @ 25 °C (77 °F). I keep the batteries in an outdoor shed,...
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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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365 views

Why copper wires submerged in salt (or fresh) water oxidize much faster while they conduct electrical current?

On a lot of flooded vehicles (salt/fresh water), I've noticed that wire that carries more current is always the one with most destruction (at the connector/splice), in comparison with lower current ...
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933 views

Why does aluminum foil “electrocute” dental fillings?

This is probably one of the weirdest questions on here. When I was a kid, I put aluminum foil in my mouth (maybe it was still attached to some food or something, I don't remember.) Anyway, it made my ...
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637 views

Why did my lemon and penny battery fail?

I followed instructions in Popular Mechanics publication for making a battery using lemons and pennies but it didn't work. I have a few ideas on why it might not have worked and would like to know ...
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562 views

Why is it important to minimize impurities when doping a semiconductor?

I was reading "Electronic Devices and Circuits" by Boylestad, and in there the author talks about how the semiconductor industry seeks to add as little impurities as possible when manufacturing ...