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).
1,583
questions
5
votes
0answers
281 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.
4
votes
4answers
601 views
Explanation for a basic decomposition of water experiment
My son is trying to write a conclusion for a basic decomposition of water experiment using a 9 V battery (with a test tube placed over each terminal) placed inside a salt water solution. The results ...
4
votes
2answers
7k views
Why can higher voltages lead to less efficient electroplating?
I was reading up on electroplating and I came across some things which really confused me:
Faraday's First Law says that the amount of metal plated onto the cathode is proportionate to the current, ...
4
votes
2answers
175 views
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 &&...
4
votes
2answers
6k 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?
4
votes
2answers
466 views
Will galvanic corrosion happen on a ring made of gold and bronze?
I have recently got a custom-made ring from a jeweler. It’s made from a byzantine-period bronze ring enveloped in a gold bangle. The bronze ring is “glued” onto the gold ring through some kind of ...
4
votes
2answers
8k views
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?
4
votes
2answers
18k 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 ...
4
votes
2answers
6k views
Why do electrons follow from Zn to Cu but not Cu to Zn in the lemon battery experiment?
In the lemon battery experiment, as I understand, both $\ce{Zn}$ and $\ce{Cu}$ meet acid in the lemon, cause $\ce{Zn}$ and $\ce{Cu}$ release electrons to form $\ce{Zn^{2+}}$ and $\ce{Cu^{2+}}$.
So ...
4
votes
1answer
102 views
In a battery, what happens to LiCoO2 when the lithium leaves? It becomes CoO2?
What chemical compound exists at the cathode of a lithium-ion battery when the lithium is not there?
The cathode is usually described as $\ce{LiCoO2}$, so does it become $\ce{CoO2}$?
$\ce{CoO2}$ ...
4
votes
2answers
486 views
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}^- \...
4
votes
2answers
387 views
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$$
In case of ...
4
votes
1answer
522 views
Is a strontium-fluorine battery the highest voltage battery using pure elements?
Strontium has a very low standard electrode potential and fluorine has a very high one.
$$ E_{\ce{F2 + 2e^- -> 2F^-}} = 2.87\mathrm{V} $$
$$ E_{\ce{Sr -> Sr^+ + e^-}} = -4.10\mathrm{V} $$
In ...
4
votes
3answers
7k views
How to calculate the solubility product for PbS from galvanic potential?
Knowing that at 25 °C the following galvanic cell:
$$\ce{Pb~|~Pb(NO_3)_2~1M~||~PbS~saturated~|~Pb}$$ shows an $\mathrm{EMF} =0.413~\mathrm{V}$, find the $K_\mathrm{sp}$ of $\ce{PbS}$.
My Approach
...
4
votes
1answer
654 views
Reduce chlorine gas
I have a simple electrolysis setup which uses aqueous sodium chloride as electrolyte. The problem is that, the setup makes tons of chlorine gas along with hydrogen (I only want hydrogen). I didn't ...
4
votes
3answers
18k views
Calculate the standard oxidation potential from given potentials
The standard electrode potentials for the following redox couples are given as: >$E_0(\ce{Fe^{2+}/Fe}) = x~\mathrm{V}$ and $ E_0(\ce{Fe^{3+}/Fe^{2+}}) = y~\mathrm{V}$
What will be potential $E_0(\ce{...
4
votes
4answers
6k views
Why is zinc deposited on copper when boiling an aqueous zinc sulfate solution?
I did an experiment where I dissolved 30 grams of zinc sulfate in water and boiled it with strips of solid zinc metal and strips of copper metal and a layer of zinc was deposited on the copper.
I ...
4
votes
3answers
1k views
No sign flipping while figuring out the emf of voltaic cell?
I learnt that for a voltaic cell, the value for the $E_\text{cell}^\circ$ when the reaction is spontaneous is given by
$$E_\text{cell}^\circ = E_\text{cathode}^\circ - E_\text{anode}^\circ, \label{...
4
votes
2answers
208 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
votes
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
votes
3answers
12k 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
votes
1answer
84 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
votes
1answer
935 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
votes
2answers
979 views
How does overvoltage affect the products of electrolysis?
When you electrolyse an aqueous solution of $\ce{NaCl},$ the product formed at cathode is $\ce{H2}$ gas (preferential discharging), but the product formed at anode is $\ce{Cl2}$ gas. According to ...
4
votes
1answer
592 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 ...
4
votes
1answer
507 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
votes
3answers
33k views
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 $\...
4
votes
1answer
166 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
votes
2answers
827 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
votes
1answer
41k 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
votes
2answers
184 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
votes
1answer
138 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 °C (77 °F). I keep the batteries in an outdoor shed,...
4
votes
1answer
724 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
votes
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
votes
1answer
881 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
votes
2answers
656 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
votes
1answer
54 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
votes
2answers
776 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
votes
2answers
2k 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
votes
1answer
715 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
votes
1answer
143 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
votes
1answer
580 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
votes
1answer
824 views
Electronegativity
Why is the Electronegativity difference for atoms in bonding uncertain while determining what the compound will be?
According to the IB(International Baccalaureate) they say that the ...
4
votes
2answers
3k 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
votes
2answers
518 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
votes
1answer
303 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 $E^⦵$ is the potential of the $A/A^{+}$ couple wrt. SHE, ...
4
votes
1answer
466 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
votes
2answers
252 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
15k 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} \\
\ce{...
