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).
1,451
questions
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597 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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2answers
16k views
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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18k views
Calculate the standard oxidation potential from given potentials
The standard electrode potentials for the following redox couples are given as: >$E_0(\ce{Fe^{2+}/Fe}) = x~\mathrm{V}$ and $ E_0(\ce{Fe^{3+}/Fe^{2+}}) = y~\mathrm{V}$
What will be potential $E_0(\ce{...
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4answers
6k views
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 ...
4
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3answers
865 views
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
$$E_\text{cell}^\circ = E_\text{cathode}^\circ - E_\text{anode}^\circ, \label{...
4
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2answers
207 views
Is water acidic enough for an redox reaction involving H+?
If you stored $\ce{Pb(NO3)2(aq)}$ in a $\ce{Cu(s)}$ container, would any reaction occur? Lead(II) ions will not react spontaneously with the copper solid as the $E^0_\mathrm{net}$ of the reaction ...
4
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2answers
2k views
Cheap metal to replace platinum in hydrogen fuel cell
Platinum is used as a catalyst in hydrogen fuel cells because it increases the efficiency. However, if I just want to make a fuel cell for demonstration purposes, I don't want to use a lot of money to ...
4
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1answer
6k views
Why does the copper anode dissolve?
In such a setup, the copper anode is known to dissolve. My question is, why? Does it not receive electrons from the $ \ce{OH^-}$ ions. And if you say that those electrons just flow to the battery, let ...
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3answers
11k views
Why can't a primary cell be recharged?
The explanation I have found is that primary cells have irreversible reactions, so passing current in the opposite direction cannot recharge the cell. But as far as I understood it, no reaction is ...
4
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3answers
15k views
Why do Electrons leave the Zinc in a Galvanic Cell
What induces electrons to leave the atoms around the part of the zinc metal in a solution to travel up along that zinc metal and above the solution, through the wire and to the copper metal and ...
4
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1answer
81 views
Reaction of an electrode
Why is the cathodic reaction of $I^-/AgI/Ag$ is $$\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}$$
4
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1answer
896 views
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 ...
4
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1answer
435 views
Is the Standard hydrogen electrode potential at T other than 298 K also zero?
The standard hydrogen electrode potential by conventional at 298Ā K is taken to be 0.00 volts.
This is what I have been taught. It talks about SHE at 298Ā K, so is the hydrogen electrode potential at a ...
4
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1answer
406 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 ...
4
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3answers
27k views
Why is mass gained at the cathode?
I'm dealing with a voltaic cell constructed like this:
(From āElectrochemistryā, chapter 19 from the book Principles of General Chemistry (v. 1.0).)
I understand that as oxidation occurs at the $\...
4
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1answer
148 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 ...
4
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2answers
814 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 ...
4
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2answers
7k views
Electrochemical cell polarity and electrodes
In an electrochemical cell, the anode undergoes oxidation and the cathode undergoes reduction. This means that the anode loses electrons while the cathode gains electrons.
However, the anode is ...
4
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1answer
40k views
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)}$$
How do I determine how many electrons are transferred in this reaction? More specifically, I need to know ...
4
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2answers
140 views
Finding EMF of a galvanic cell without standard potentials
For the galvanic cell
$$\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{AgBr}) = \...
4
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1answer
116 views
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 Ā°C (77 Ā°F). I keep the batteries in an outdoor shed,...
4
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1answer
767 views
Electrode polarity in fuel cells
I am studying fuel cells right now and I'm confused about the polarity of the two electrodes.
In the diagram below, the anode is shown as negative. However, why do $\ce{H+}$ ions move away from the ...
4
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1answer
605 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 ...
4
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1answer
2k 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 ...
4
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1answer
791 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 ...
4
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2answers
628 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 ...
4
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1answer
51 views
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)$$
...
4
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2answers
716 views
How can I balance the following equation atomically and electrically?
$$\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
votes
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
1k 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
659 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
137 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
546 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
222 views
For a copper/copper sulfate half reaction, do sulfate anions move to the anode and lose electrons?
In my (high school) textbook, there's an example on finding the charge on 1 mole of electrons, which involves performing the electrolysis of an aqueous copper (II) sulfate using a copper anode and a ...
4
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1answer
176 views
Subtracting standard electrode potentials
As far as I'm aware, if we construct a half cell ($\ce{A + e- <=> A-}$) under standard conditions then the standard electrode potential $E^ā¦µ$ is the potential of the $A/A^{+}$ couple wrt. SHE, ...
4
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3answers
2k views
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 + ...
4
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1answer
422 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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2answers
233 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
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1answer
12k views
Which half cell equation do you switch when calculating E° cell?
Given the following standard potentials calculate the overall $E^\circ_\mathrm{cell}$:
$$
\begin{align}
\ce{Pb(SO4)(s) + 2 e- &ā Pb(s) +SO4^2-(aq)} &\quad E^\circ &= \pu{-0.356 V} \\
\ce{...
4
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1answer
890 views
Why does two nails of the same material not produce electricity when placed in saltwater?
If I put two the same nails in a saltwater why could it not produce electricity when I put the metal aluminum and copper it produces electricity?
4
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3answers
953 views
Irreversible chemical reaction in a battery
Inside an ideal battery, the chemical reaction is reversible (at equilibrium), thus the oxidation-reduction reaction $\ce{Zn + Cu^{2+} -> Zn^{2+} + Cu}$ is happening in both ways at the same rate ...
4
votes
1answer
86 views
Is it possible to recycle an alkaline battery?
Is it possible to recycle an alkaline battery?
The application I am thinking about is that in 3rd world countries often access to western markets is limited. You can't just pop into a store and buy ...
4
votes
1answer
180 views
How to identify which of two given electrodes with corresponding solutions is reducing more?
For the sake of the question, letās assume that you are provided with two labelled rods of the pure metals $\ce{A}$ and $\ce{B}$ and two unlabelled bottles containing $\pu{1.0 mol dm-3}$ aqueous ...
4
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1answer
329 views
How does the MG811 sensor work?
The MG811 is an electrochemical sensor that measures $\ce{CO2}$. I think is something like a redox reaction but i don't understant how it produces $\ce{e-}$ so i can read them and get the $\ce{CO2}$ ...
4
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1answer
80 views
If given a half reaction, how do you determine if an element can exist in a acidic conditions?
I was given the formulas,
$$\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
27k 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
2k views
Standard electrode potential for electrolytic vs galvanic cells
Whys is the standard electrode potential (-) for electrolytic cells but positive for (+) galvanic cells.
If EĀ°cell > 0, then the process is spontaneous (galvanic cell)
If EĀ°cell < 0, then ...
4
votes
2answers
614 views
What's the name of this electrolysis device?
I've seen it in a couple of videos, it's used to electrolyze water in 2 different containers at the same time to make a comparison and thus is very handy.
What is it called (besides just a ...
4
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1answer
69 views
Why is Sodium Transported Across the Cation Exchange Membrane in the Chlor Alkali Process?
In the Chlor Alkali Process, a sodium ion is transported across a cation exchange membrane to create NaOH in the Anode Chamber:
The Half reactions are:
2Clā ā Cl2 + 2eā
and
2H2O + 2eā ā H2 + 2OHā
and ...
4
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1answer
177 views
How is the formula of mean activity coefficient derived?
The mean activity coefficient is defiend as follows:
$$\gamma_\pm = (\gamma_+\gamma_-)^{1/2}.\tag{1}$$
If Debye-HĆ¼ckel equation
$$-\log\gamma_i = 0.5z_i^2\mu^{1/2}\tag{2}$$
is used, then the mean ...
