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).
1,225
questions
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Balancing redox equation with oxygen on both sides?
The problem is to balance this equation in an acidic medium.
$$\ce{As2O3 (s) + NO3- (aq) -> H3AsO4 (aq) + N2O3 (aq) }$$
However, I am getting stuck balancing the oxygens after dividing them ...
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1answer
48 views
Salt bridge confusion :(
How exactly does a salt bridge close the circuit? I understand its role of neutralizing the solustions but I can't see how it forms a complete circuit. Do charges flow back to the anode through it? ...
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1answer
350 views
Electrode potential for metal-metal ion and metal-metal insoluble salt-salt ion electrode
So I read it in a book that
The potential of metal-metal ion electrode and metal-metal insoluble salt-salt anion electrode is same while their standard potentials are not same. Standard potential ...
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0answers
63 views
What could be causing my cyclic voltammograms to have a sloped scan?
I am running a CV (cyclic voltammogram) in a two compartment bulk electrolysis cell with pH 7 phosphate buffer (0.5 ion concentration) and a napheon membrane separating the two compartments. I'm using ...
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2answers
7k views
Why does increasing number of salt bridges increase voltage of electrochemical battery?
In an experiment, I set up a cell with lead nitrate (w/ lead electrode) and zinc sulfate (w/ zinc electrode), with a salt bridge containing potassium nitrate.
I observed that by increasing the number ...
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22 views
What Ion gets reduced in this aqueous electrolysis?
In an electrolysis of tin(II) iodide ($\ce{SnI2}$) with led cathode and nickel anode, why is it that the tin ion gets reduced and not the nickel ion?
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2answers
244 views
Leaching of copper using zinc
Why can we not use zinc for extracting copper from a solution containing $\ce{Cu^2+}$ ions even though it is a better reducing agent than $\ce{Fe}$?
I am studying metallurgy and I cannot understand ...
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26 views
Electric potential of a redox reaction (without solids)
I need someone to help me with a problem:
We have a solution which is $\pu{0.1 M}$ of $\ce{KMnO4}$ and $\pu{0.1 M}$ $\ce{Fe^2+}$ and has $\mathrm{pH}=0$. Given the electrical reduction potential of ...
2
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1answer
97 views
Why do Cu⁺ ions spontaneously form copper metal and Cu²⁺ ions in solution?
The standard electrode potentials for three reactions involving copper and copper ions are:
$$
\begin{align}
\ce{Cu^2+(aq) + e- &-> Cu+(aq)} &\quad E &= \pu{+0.15 V} \\
\ce{Cu^2+(...
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70 views
Why does the following “Battery” experiment work?
I did the following experiment:
Experimental setup:
Two electrodes (one made out of Iron,the other made out of Copper)
are put into a (bluish) Copper(ii) sulfate lotion.
Then, one connect a ...
5
votes
3answers
9k views
Express the maximum work from a voltaic cell
The net cell reaction of an electrochemical cell and its standard potential is given below:
$$\ce{ Mg + 2Ag+ ->Mg^{2+} + 2Ag} \ \ \ \ \ \ \ \ E^\circ=3.17\:\mathrm{V}$$
The question is to find the ...
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3answers
33k views
Why is the reaction between potassium permanganate and hydrogen peroxide spontaneous?
When hydrogen peroxide is mixed with potassium permanganate, oxygen gas and water vapour are formed, according to the reaction (source):
$$\ce{2MnO4- + 3H2O2 -> 2MnO2 + 2H2O + 3O2 + 2OH-}$$
This ...
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0answers
36 views
Can carbon dioxide be used as oxidant for iron?
Determine whether it is possible for $\ce{CO2}$ to be an oxidant for $\ce{Fe}$. Justify your choice by comparing the corresponding half reactions.
I found the following half-reactions, both on ...
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1answer
98 views
Pale blue species forming during electrolysis of NaHCO3
I have a solution of 3500 ml $\ce{H2O}$ + 454 g $\ce{NaHCO3}$ in electrolysis at a potential of 12.5V using a lead anode and copper cathode. The surface areas aren't measured but they are enormous. I ...
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1answer
44 views
How can I find the emf of a cell given the individual reduction and oxidation reactions and their respective potentials? [duplicate]
If I am given the individual oxidation and reduction half-equations, how can I find the emf of the combination? For example:
$$
\begin{align}
E^\circ(\ce{Fe^3+}/\ce{Fe^2+}) &= \pu{0.77 V}\\
E^\...
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1answer
2k views
Changing Temperature of a Galvanic/Voltaic Cell: Should I wait for the electrodes to also change in temperature?
I'm conducting an experiment where I change the temperature of the sulfuric acid in a lead acid storage cell. My one question in controlling the variables is that should I let the electrodes also ...
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1answer
56 views
In a galvanic cell, why do electrons move through the wire from zinc to copper?
I understand that there is aqueous $\ce{Cu^2+}$ in this scenario which pulls on the electrons from the zinc causing the electrons to move through the wire, but how does the electronegativity of $\ce{...
2
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1answer
103 views
Cathodic protection of active metals
Cathodic protection prevents the removal of positive form the metal surface by applying a negative charge to the metal.
Is is possible to prevent the reaction of an active metal (i.e. sodium) with ...
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0answers
100 views
Degradation of carbon anode in electrolysis of copper sulfate
I'm electrolysing a copper sulfate solution with a 12 volt DC supply using two carbon electrodes. The anode is reducing in mass and becoming thinner. Is there any way I can overcome this problem?
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0answers
50 views
Electrodes of the second kind
An electrode of the second kind consists of a metal sheet coated with a layer of a slightly soluble salt of the metal of which it is made, immersed in an electrolytic solution: the last one must have ...
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1answer
11k views
How come diluting a cell decreases the voltage?
I just want to know why, if we dilute a cell with water, it decreases the voltage. Assume it is a galvanic cell.
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0answers
71 views
Electrolytic cell to remove soft solder from silver?
Hi my chemistry is pretty dire but have vague idea that an electrochemical cell could be used to remove soft solder (lead/tin probably) from a piece of sterling silver in need of a repair.
The ...
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votes
2answers
22k views
Why does temperature affect cell potential?
The Nernst equation describes the relationship between cell potential and temperature. But why does temperature affect cell potential?
My understanding is that the collision model of kinetics is not ...
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votes
1answer
45 views
Why is it bad to charge a phone to 100%? [duplicate]
I see everywhere that a phone should ideally be between 20 and 80% to work efficiently, but I don't understand why, in an electrochemistry point of view. (I'm not talking about the fact that ...
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2answers
5k 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 ...
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1answer
33 views
Which conductivity law should I use to calculate the conductivity of a solution with high/low concentration?
I have a set of NaCl solutions with concentrations ranging from 0.05 M to 0.1 M.
I have been trying to calculate the conductivity of these solutions and compare the obtained values with the ...
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1answer
53 views
What is the balanced chemical equation for a redox reaction between a lithium-cobalt battery and a graphite electrode?
I'm doing a project for my last year of secondary school on lithium cobalt batteries and got confused about the equation.
This is the only equation I can find (source: www.science.org.au):
\begin{...
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votes
1answer
1k views
Cell notation for the lead-acid battery
Reactions for the lead acid battery are:
$$
\begin{array}{}
\text{Oxidation}&\ce {Pb(s) + HSO4^-(l) &-> PbSO4(s) + H+(l) + 2e-}\\
\text{Reduction}&\ce{PbO2 + HSO4^-(l) + 3H+(l) + 2e- &...
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0answers
57 views
half equations for a lead-acid cell
we are learning about galvanic cells. I would like to know the half equations and overall equation that occurs in this lead acid cell. so far my understanding for the oxidisation section is that in a ...
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45 views
Negative Voltage for Full Redox Reaction?
I have a question about voltages including redox reactions. I know that half equations may have negative voltages when choosing what is undergoing reduction, and what is undergoing oxidation in a ...
3
votes
1answer
92 views
Current and reversible heat in battery reaction
In the book Battery Technology Handbook by Kiehne [1] (Google Books) on page 21, equation (32):
The reversible heat effect per time unit can be related to current flow, because each multiple of the ...
3
votes
2answers
145 views
Energy balance in battery thermodynamics
I am trying to understand the derivation of a general energy balance in battery thermodynamics. The following relation is frequently found to determine the heat generation of a battery:
$\dot{Q} = \...
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1answer
83 views
Electrolytes are ionic compounds that conduct electricity [closed]
Electrolytes are ionic compounds that conduct electricity, or the flow of charged particles, when dissolved in water. This occurs via the separated ions acting as those charged particles, or charge ...
3
votes
1answer
345 views
Calculating the concentration of copper(II) from a non-standard cell potential
A galvanic cell consists of a standard hydrogen electrode and a copper electrode.
\begin{align}
\ce{2 H+ (aq) + 2e- &-> H2 (g)}&
E^\circ &= 0.00\ \mathrm{V}\\
\ce{Cu^2+ (aq) + 2 ...
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0answers
21 views
Rate of cathodic reaction vs Tafel slope
One of my reference engineering books says that for the cathodic protection process (in seawater):
Al $\rightarrow$ Al$^{3+}$ + $3e^-$ (anode, setting the protection potential at about -900 mV SCE)
...
2
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1answer
73 views
Why should I not use different battery types together?
Everyone knows about this but I'm curious about why one should never mix batteries of different types. By type I mean the same shape of the cell like AAA but with different chemical reactions and ...
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1answer
86 views
Is it possible to electroplate from a gallium anode?
I have been looking at some papers on electro-deposition of iron gallium alloys and these all use solutions made up of Fe and Ga sulphates.
I am just curious as to why perhaps an anode made of one of ...
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0answers
44 views
Can I make an ionic liquid from glycerin and zinc sulfate?
Can I make an ionic liquid (dissolved salt without water) by combining zinc sulfate and glycerin? I've been using 1 M $\ce{ZnSO4}$ as my electrolyte in supercapacitor study. Works very well up to ...
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1answer
266 views
What happens if you put a piece of copper into a solution containing Al3+ ions?
This is a question in my studies, and I am a little bit confused! I would think it happens nothing because copper is below aluminium in the reactivity series, right?
3
votes
1answer
251 views
How to calculate the electromotive force of a silver chloride/ silver bromide cell?
For the galvanic cell: $\ce{Ag|AgCl(s)|KCl(0.2M)||KBr(0.001M)|AgBr(s)|Ag}$, calculate the electromotive force (EMF) generated.
$K_\mathrm{sp}(\ce{AgCl}) = 2.8\times10^{-10}$;
$K_\mathrm{sp}(\ce{...
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1answer
245 views
Why does increasing the concentration of oxidizing agent decrease the E° in a galvanic cell?
In a galvanic cell, when we add ions of the oxidation agent (in this example, Zn2+) to the anode solution, it decreases the cell potential.
However, if the Zn2+ ions aren't involved in the redox ...
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1answer
208 views
Replacing Salt Bridge with Platinum Sheet
What would happen, if in a galvanic cell, the salt bridge is replaced by an inert platinum sheet?
Would charges accumulate on the sheet? Would the cell still work, and produce less emf than earlier, ...
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1answer
8k 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} \\
...
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59 views
Regarding Standard Electrode Potentials
If the standard hydrogen electrode (SHE) is set arbitrarily to have a potential that is equal to 0 V, and has an absolute real potential. Then, in electrochemistry, how are the electrode potentials of ...
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62 views
What is the voltage dependence of the thickness of oxide coating through anodising?
In titanium anodising, solid titanium reacts with the oxygen formed at it's surface (to form titanium(IV) oxide or $\ce{TiO2}$) through the electrolysis of water. Experimentation and research has ...
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2answers
1k views
Salt Bridges/Porous Disks
I am slightly confused about the concept of a salt bridge/porous disk. I understand that these are necessary in a galvanic cell since there is a charge buildup and the salt bridge and porous disks ...
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0answers
23 views
Polarity of Cell Electrodes [duplicate]
I understand that the anode in a galvanic/voltaic cell is considered to be 'negative' while the cathode is 'positive'. However, in an electrolytic cell, the cathode is 'positive' while the anode is '...
2
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0answers
16 views
Why do electrocatalysts based on polyoxometalates and carbon materials have a weaker activity/performance in acidic media?
I am testing now some doped N and S doped carbon nanomaterials alone and immobilized in POM for the purpose of developing a nanocomposite that can serve as an electrocatalyst for energy-related ...
3
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1answer
172 views
Pourbaix diagram and the order of the species
Figure 1. Pourbaix diagram of iron (Source)
The line between $\ce{Fe}$ and $\ce{Fe^2+}$ is there because the potential $\ce{Fe/Fe^2+}$ is $\pu{-0.44 V}$. The same applies for $\ce{Fe^2+/Fe^3+}$ with $...
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84 views
Can static electricity damage solar cells?
How does static electricity damage common solar cells making them less photo reactive? At watt voltage and/or amps would change the chemistry of the common solar cell?
I want to think that as long ...
