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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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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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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168 views

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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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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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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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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Redox potential of a lead–acid battery

In the German Wikipedia there are two reactions on the poles of the battery shown with the following potentials: $$ \begin{align} \ce{Pb + SO4^2- &-> PbSO4 + 2 e-} &|\pu{-0.36 V}\\ \ce{...
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Decreasing magnitude of peaks in cyclic voltammogram?

I'm in an instrumentation course and we covered cyclic voltammetry earlier in the semester and will be doing an experiment in CV next week. My question is this: If you have a reaction and sweep the ...
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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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How would using different salts in a salt bridge effect the voltage generated by a voltaic cell?

If I use a range of different nitrate solutions (e.g. calcium nitrate, iron nitrate) for the salt bridge in a voltaic cell, what effect would it have on the flow of ions in the voltaic cells? Will ...
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In a simple chemical cell

Why do the electrons, arising from the oxidation of the anode, flow through an external circuit? Why does it not just flow through the electrolyte and reduce the cathode? Why do the electrons give the ...
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Standard hydrogen electrode, why hydrogen?

Why is the hydrogen electrode used as the reference to set electrode potentials? Could any other element be used instead?
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Iodometric titration of copper – standard electrode potentials

Upon inspection of the standard electrode potentials for the half reactions for both $\ce{Cu^2+}$/$\ce{Cu+}$ and $\ce{I2}$/$\ce{2I-}$, it becomes apparent it should be the iodide ions that act as the ...
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how to measure dissolved oxygen?

How do you measure dissolved oxygen reliably in a culture of cells? This page has info on one sensor: http://water.me.vccs.edu/concepts/domeasure.html how would you know that this sensor is working - ...
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Standard electrode potential for electrolytic vs galvanic cells

Whys is the standard electrode potential (-) for electrolytic cells but positive for (+) galvanic cells. If E°cell > 0, then the process is spontaneous (galvanic cell) If E°cell < 0, then ...
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Why is there no salt bridge in electrolytic cell?

I was just wondering why is there no salt bridge in electrolytic cell? It is said that electrodes are in a common electrolyte solution without salt bridge. However, when I searched the image of the ...
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Calculating the electrode potential from thermochemical data

How can I calculate the electrode potential from thermochemical data? My attempt: I know that the electrode potential is dependent on the enthalpies of: atomisation, first ionisation, second ...
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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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Unknown white precipitate in electrolysis of water

I was electrolysing water using a copper anode and zinc cathode. The water was from the tap and where I live is very hard. I was using about 20V between the two electrodes. As I applied the voltage,...
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Is the subtrahend in the Nernst equation related to ohmic drop?

Let us consider the Nernst equation $$E= E^\circ -\frac{2.303RT}{nF} \log Q$$ which once at $\pu{298.15 K}$, is the equivalent of $$E= E^\circ - \frac{0.059}{n} \log Q .$$ Does the part of the ...
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How can Nernst equation apply in this redox reaction?

$$\ce{CuSO4 + Zn -> ZnSO4 + Cu}$$ What is the cell potential of the voltaic cell with copper and zinc electrodes if the system is at 50 degrees and the solutions are both at 1 mol? How can it be ...
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Cathode + Anode + Rechargeable battery

I'm confused by the following from this webpage: The cathode is a metal oxide and the anode consists of porous carbon. During discharge, the ions flow from the anode to the cathode through the ...
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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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How much electricity could be generated by a person's stomach acid?

Motorola has a device that is powered by stomach acid. Given that a battery consumes the electrolyte as it generates a charge, how much power could be generated using a device such as this? Let's ...
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Measuring distance in a conductive liquid

What is needed to measure distance between two electrodes imersed in seawater ? I have tried measuring the voltage across the path (a suposed resistance) with a constant current source (about 10uA) ...
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Galvanic corrosion between nickel brass nut and stainless bolt

I am planning to install something on a boat that will be in salt water, and my question is, will the nickel plated brass fastener not corrode if I connect it to stainless steel? I looked it up on ...
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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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How exactly does a battery work (specifically Pb/H2SO4/H2SO4/PbO2 lead acid battery)?

Specifically talking about the lead-acid battery, I understand (or think I understand) this much: The anode, in the presence of the electrolyte, $\ce{H2SO4}$ will be oxidised: $$\ce{Pb (s) + SO4^2- (...
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Current in a galvanic cell

I was looking through chemistry textbooks to find out how to determine how much current a galvanic cell should generate and what affects that current value. However, I did not find anything: textbooks ...
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Electrolysis of water for demonstration: ideal electrolyte for safety, stability, conductivity, and ease of maintenance

I'm developing a system for educational purposes where electrolysis of water takes place. The aim is to practically show how electrical energy can be converted to mechanical, by electrolyzing water, ...
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Does battery self discharge when connected?

I am an electric engineer, and I read about battery self discharge phenomenon. I was wondering whether a battery self discharge rate is the same when it is unconnected (i.e. in storage) and connected (...
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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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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{nFAm_O}...
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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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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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Can I anodize an aluminum coating on steel to have better corrosion inhibition for the steel?

I am planning to coat aluminum on steel and I want to give the steel its maximum corrosion protection. Is anodizing the coating necessary?
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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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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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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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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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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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