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).
1,181
questions
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The property F in an equation for chemical potential
While studying the lamba sensor that works on yttria-strabilised-zirconium (YSZ) I came across the following equation:
$$p_{O_2}^{gas}=p_{O_2}^{ref} \cdot \exp\left(\frac{4FV_{ref}}{RT}\right)$$
...
4
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2answers
9k views
Why can't a primary cell be recharged?
The explanation I have found is that primary cells have irreversible reactions, so passing current in the opposite direction cannot recharge the cell. But as far as I understood it, no reaction is ...
4
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2answers
621 views
How can I balance the following equation atomically and electrically?
$$\ce{C2O4^2- + MnO2 -> Mn^2+ + CO2}$$
I think that the half reactions are
$$\ce{C2O4^2- -> CO2}$$
$$\ce{MnO2 -> Mn^2+}$$
I am supposed to balance these by adding water, $\ce{H+}$ atoms ...
4
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1answer
9k views
Standard Hydrogen Electrode
Could someone, please, explain to me how the standard
Hydrogen Electrode works and how it is used to measure electrode potentials? Also, why does it have a potential value of zero?
4
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2answers
986 views
Heat given off from an electrochemical cell compared to mixing reactants
My confusion regarding the difference between the heat given off in a reaction that takes place in an electrochemical cell compared to in a beaker/appropriate container when the reactants are simple ...
4
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1answer
568 views
Will I get bromine by electrolysis of the brine from the Dead Sea?
I know that electrolysis of a saturated solution of sodium chloride with an inert anode (eg., graphite) is a handy way to obtain pure chlorine. I have a sample of saturated salt solution from the Dead ...
4
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1answer
130 views
How to prove that reaction is possible [closed]
I have been given task to write possible reaction equations, determine oxidizer, reducer, write corresponding electron-equations and calculate electromotive force (I do not know if that is what you ...
4
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1answer
468 views
Why do aqueous solutions always have to be electrically neutral?
I was reviewing some analytical chemistry and stumbled upon a section that explained the imperfection of using a salt bridge.
It said that the using dissimilar ions is a problem because in, for ...
4
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2answers
2k views
Can we separate positive ions from negative ions in a solution?
Can we make a solution containing only positive ions by using electrodialysis but instead of using 2 kinds of membrane (one blocks the positive ions and one blocks the negative ions) we can use only ...
4
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1answer
242 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 ...
4
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1answer
289 views
Clarification about Frost diagram y-axis conventions?
I was looking at the Frost diagram of Manganese, and on the UC Davis ChemWiki, I see this one:
However, the one straight from my textbook, "Descriptive Inorganic Chemistry" (Overton), looks like this:...
4
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1answer
624 views
Why does two nails of the same material not produce electricity when placed in saltwater?
If I put two the same nails in a saltwater why could it not produce electricity when I put the metal aluminum and copper it produces electricity?
4
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3answers
817 views
Irreversible chemical reaction in a battery
Inside an ideal battery, the chemical reaction is reversible (at equilibrium), thus the oxidation-reduction reaction $\ce{Zn + Cu^{2+} -> Zn^{2+} + Cu}$ is happening in both ways at the same rate ...
4
votes
1answer
79 views
Is it possible to recycle an alkaline battery?
Is it possible to recycle an alkaline battery?
The application I am thinking about is that in 3rd world countries often access to western markets is limited. You can't just pop into a store and buy ...
4
votes
1answer
139 views
How to identify which of two given electrodes with corresponding solutions is reducing more?
For the sake of the question, let’s assume that you are provided with two labelled rods of the pure metals $\ce{A}$ and $\ce{B}$ and two unlabelled bottles containing $1.0\ \mathrm{mol\ dm^{-3}}$ ...
4
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1answer
286 views
How does the MG811 sensor work?
The MG811 is an electrochemical sensor that measures $\ce{CO2}$. I think is something like a redox reaction but i don't understant how it produces $\ce{e-}$ so i can read them and get the $\ce{CO2}$ ...
4
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1answer
73 views
If given a half reaction, how do you determine if an element can exist in a acidic conditions?
I was given the formulas,
$$\begin{alignat}{2}
\ce{MnO4^2- \;&<=> MnO4- + e-}\quad &&E^\circ = -0.56\ \mathrm{V}\\
\ce{MnO2 + 2H2O \;&<=> MnO4^2- + 4H+ + 2e-}\quad &&...
4
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2answers
26k views
Why use a salt bridge at all in an electrochemical cell?
I was reading about electrochemical cells and I really don't understand why a salt bridge is needed. Can't you just combine the solutions? I've found a lot of webpages explaining electrochemical cells ...
4
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1answer
1k views
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 ...
4
votes
1answer
773 views
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 ...
4
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2answers
9k views
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 ...
4
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2answers
9k views
Why can we disregard stoichiometric coefficients when computing reduction potentials?
Example:
A $Cd // Cr$ Galvanic cell has redox half reactions:
$\ce{Cd^{2+} + 2e^- -> Cd}$
$E_{cell}$ = -0.4
$\ce{Cr^{3+} + 3e- -> Cr}$
$E_{cell}$ = -0.7
Balanced equation of reaction ...
4
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1answer
1k views
Gibbs free energy and electrical potential
The relation between the Gibbs free energy and the electrical potential is:
$$\Delta G=-zFE$$
$z$ is the valence of the electrochemical reaction and $F$ is the Faraday constant.
If at equilibrium ...
4
votes
2answers
339 views
In a single cell battery, is voltage exactly equal to cell potential?
I've been researching electrochemical cells. In chemistry-focused sources, you usually see the potential difference between the electrodes referred to as cell potential, but in engineering/industrial ...
4
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1answer
1k views
Calculating the electrode potential from thermochemical data
How can I calculate the electrode potential from thermochemical data?
My attempt: I know that the electrode potential is dependent on the enthalpies of: atomisation, first ionisation, second ...
4
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2answers
218 views
Galvanic cell chemistry
I made a galvanic cell with the anode electrode being aluminum and the electrolyte being aluminum sulfate. The salt bride was magnesium chloride. I am a little confused on what my oxidation equation ...
4
votes
1answer
7k views
Which half cell equation do you switch when calculating E° cell?
Given the following standard potentials calculate the overall $E^\circ_\mathrm{cell}$:
$$
\begin{align}
\ce{Pb(SO4)(s) + 2 e- &→ Pb(s) +SO4^2-(aq)} &\quad E^\circ &= \pu{-0.356 V} \\
...
4
votes
1answer
544 views
producing ozone through electrolysis of water
I would like to produce low concentrations of ozone through electrolysis of water. The standard setup to do this uses a graphite electrode and a platinum electrode in an $\ce{H2SO4}$ solution. ...
4
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1answer
3k views
Describe the function of a salt bridge, What would happen if the half-cell compartments of a galvanic cell were not connected?
I know, The primary function of a salt bridge is to complete the circuit, so that charge can flow from one half-cell to the other. The second function is to balance the mass by allowing the anions to ...
4
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1answer
194 views
What can we say about the Gibbs free energy if it decreases or not?
[Sorry if the question looks trivial but I have thought about it for days and red a number of books all with no success.]
In almost every thermodynamics book that has something to say about chemical ...
4
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2answers
1k views
Cathodic protection of aluminium
I am planning an experiment for a chemistry class about corrosion. I am going to show how different prevention methods affects the corrosion of iron and aluminium parts using bleach as the oxidizer.
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4
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1answer
2k views
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 ...
4
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1answer
94 views
What is the effect of Helium-based surroundings (99% Helium) on electrochemical gas sensors?
I am currently working on a project measuring gas composition of car exhaust. In order to dilute the gas concentration down to something electrochemical sensors can read, I diluted the sample with ...
4
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1answer
75 views
What is A in the following equation
This equation describes the total current in bulk solution in a battery caused by migration in the electrolyte.
Then the source says what A is: In the bulk solution (away from the electrode), ...
4
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1answer
173 views
Help me understand electrochemistry and batteries
I have a brief understanding of how batteries work, but there are still some things that I can't put together. Therefore I would like to ask for help in understanding how batteries work. Every time I ...
4
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1answer
142 views
Do dendrites effect lithium-ion polymer batteries?
Do dendrites effect lithium-ion polymer batteries?
I recently came across this video which shows dendrites at a microscopic level durring the charge and discharge cycles of a standard Li-Ion battery.
...
4
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1answer
601 views
Electrical double layer
I am seriously confuse with the sign of electric field in the electrical double layer. Say zinc is dipped into the zinc sulphate solution. Then why the electrical double layer has positive sign in the ...
4
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1answer
1k views
Why do electrolytic concentrations affect voltage in electrochemical cells?
I know that the voltage of a cell is calculated via the Nernst Equation as $$E_\text{cell}=E^\circ-\frac{RT}{nF}\ln Q_\mathrm r$$ where $Q_\mathrm r$ represents $\frac{\text{concentration at the anode}...
4
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1answer
125 views
Finding membrane potential equation using the Nernst equation?
I am very new to electrochemistry and ion selective electrodes. The membrane potential of an ion selective electrode is given by $$E=\frac{RT}{nF}\ln{\frac{c_2}{c_1}}$$
Where R is universal gas ...
4
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1answer
229 views
EMF measured while verification of Nernst equation keeps on increasing
I was doing this experiment to verify Nernst equation in my school's lab. I had two beakers one with $\ce{ZnSO4}$ and the other with $\ce{CuSO4}$ both having a concentration of $1~\mathrm{M}$. I had a ...
4
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1answer
112 views
Negative Ohm reading from a Electrochemical reaction?
The purpose of my experiment is to determine which salt is the best electrolyte. The setup is a tarnished spoon (Ag2S) is placed on top of thin plastic pieces that separate it from a container coated ...
4
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2answers
351 views
Lithium-ion batteries
I understand what occurs on a regular Li-ion battery - the positive Lithium ion moves from one electrode to the other of the battery. But what is exactly the physical mechanism for this intercalation ...
4
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1answer
281 views
Making a non-CN dissolved gold solution ideal for electroplating
I've had success electroplating $\ce{Ni}$ and $\ce{Cu}$, but interestingly never $\ce{Al}$. My focus here is on plating with $\ce{Au}$, specifically onto an $\ce{Ni}$ surface.
In general from my own ...
4
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1answer
70 views
Respect to other chemicals in reduction/oxidation potentials
From what I understand, the standard reduction/oxidation potential table is based on the hydrogen half reaction which makes a reduction and oxidation potential of 0 respectfully.
In a research ...
4
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1answer
742 views
Deriving goldman equation
So I've been trying to follow the derivation of the Goldman-Hodgkin-Katz equation on Wikipedia (https://en.wikipedia.org/w/index.php?title=Goldman_equation ) - I can follow it through after it sets up ...
4
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1answer
298 views
Intuitive understanding of standard electrode potential
I have read many books on standard electrode potential and they define the term in various ways but I just can’t seem to get an intuitive idea of it.
$$\ce{Cu^2+ + 2e- <=> Cu}$$
Standard ...
4
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1answer
4k views
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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0answers
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Meaning of electrochemical vs nonelectrochemical steps
Can someone please explain to me what is meant by an electrochemical reaction step and how it differs from a nonelectrochemical reaction step in the same overall reaction in the context of ...
4
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0answers
58 views
Type of floor for a chemistry lab [closed]
I'm currently building a small chemistry lab and I'm wondering about which type of floor would be the best to use. Currently I'm mainly doing electrochemistry experiments with lithium and other metals....
4
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0answers
630 views
Concept of Limiting Current
I am investigating the current output from an electrochemical cell. The electrochemical cell can be broken down into several stages, for example:
Diffusion of reactants across a capillary
Diffusion ...
