Stack Exchange Network

Stack Exchange network consists of 175 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

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).

0
votes
0answers
17 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
votes
2answers
214 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 ...
-1
votes
0answers
32 views

Why does the voltage of a galvanic cell increase as the concentration of the solutions increases in a 1:1 ratio? [on hold]

We know that voltage is potential energy per charge, and we also know that galvanic cells generate electricity from energy released from the redox reactions on the electrodes. So if the concentration ...
0
votes
1answer
67 views

Does reduction/ oxidation take place separately at a half cell electrode?

In the redox reaction chapter, we learn that oxidation and reduction go hand in hand. The oxidising agent oxidises by accepting the electron released by the reducing agent and gets reduced in the ...
2
votes
1answer
61 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+(...
0
votes
0answers
22 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
8k 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 ...
5
votes
3answers
29k 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 ...
-1
votes
1answer
22 views

Lead acid battery reactions [on hold]

Where did the other electron come from in the following first equation, looks like one of them came from "H+"?. I see that $\ce{HSO4}$ is -1 but that $\ce{SO4^2-}$ simply creates sulfate with Pb as ...
1
vote
0answers
35 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 ...
1
vote
1answer
84 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 ...
0
votes
1answer
33 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^\...
0
votes
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 ...
0
votes
1answer
31 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{...
-1
votes
0answers
16 views

Theoretical Experiment — I need help with building a galvanic element with limited materials and chemicals? [closed]

I was given this experiment to do theoretically with some chemicals and materials, and the idea is to maximize the voltage you get from the chemicals that you use in the experiment together with the ...
0
votes
1answer
120 views

Do We change sign of electrode potential when reversing an equation?

I have a cell equation as: $$\ce{2Cr^0 + 3Cd^2+ -> 2Cr^3+ + 3Cd^0}$$ I am provided the standard reduction potentials as: $$\begin{align}\ce{Cd^2+ + 2e- &-> Cd} && E= \pu{-0.4V}\...
2
votes
1answer
101 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 ...
0
votes
0answers
28 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?
0
votes
0answers
16 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 ...
3
votes
1answer
10k 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.
0
votes
3answers
84 views

Is it possible to generate electricity by using two inert electrodes in a galvanic cell?

The Daniell cell has two active electrodes, meaning that both the copper and the zink electrodes participate in the redox reaction. However, in a lemon battery for example, the copper electrode is ...
3
votes
0answers
47 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 ...
9
votes
2answers
20k 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 ...
-2
votes
1answer
36 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 ...
-1
votes
0answers
20 views

How to find the concentration of metal ions at equilibrium when a metal rod is dipped in it's own ion's solution?

Suppose I were to dip a sufficiently thick zinc rod in a zinc sulphate solution and leave it until an equilibrium sets in where the rod gets eaten a little and the concentration of zinc ions in the ...
5
votes
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 ...
1
vote
1answer
24 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 ...
1
vote
1answer
43 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{...
2
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- &...
0
votes
0answers
15 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 ...
0
votes
0answers
17 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
75 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
111 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} = \...
0
votes
1answer
27 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
300 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 ...
2
votes
0answers
15 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
votes
1answer
2k views

Why does NaCl act as a catalyst for the reaction of CuSO4 + H2O + Al?

I am analyzing a reaction between water sulfate copper and aluminum. A chunk of $\ce{Al}$, e.g., aluminum foil. I realize that a layer of $\ce{Al2O3}$ forms on the surface of the $\ce{Al}$, ...
7
votes
2answers
754 views

Nernst equation for a fuel cell when gases are stored separately

I have run some tests with a PEM fuel cell and the voltage we have found was $1.44\ \mathrm{V}$. Given that the standard potential for a fuel cell is $1.229\ \mathrm{V}$ what is causing the difference ...
2
votes
1answer
41 views

Would a salt bridge work through which the ions could not diffuse into the half cells?

Instead of covering the ends of the salt bridge in an electrochemical cell with a membrane, one could also plug them on both sides with a conductive non-porous material, for example gold, which doesn'...
2
votes
1answer
64 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 ...
0
votes
1answer
28 views

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 ...
1
vote
1answer
29 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 ...
0
votes
0answers
30 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 ...
3
votes
2answers
178 views

Is there a potentiometric method for monitoring salt formation in organic solvent?

I work in a pharmaceutical R+D lab, and currently aim to develop a validatable potentiometric method for determining the optimal amount of acid to add to a basified small organic molecule for ...
0
votes
1answer
100 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?
1
vote
1answer
68 views

Is a discharged battery in a state of chemical equilibrium?

A reaction that has reached chemical equilibrium no longer shows changes in reactant and product concentrations, but forward and reverse reactions are still going on. I'm confused whether a completely ...
2
votes
1answer
46 views

Why does magnesium deposit during electrolysis of a molten mixture of MgI2 and AlBr3?

During the electrolysis of mixed salts, I read, and was taught, that the cation with a higher ionization energy would deposit at the cathode. I was also told that you cannot use the standard electrode ...
3
votes
1answer
177 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{...
1
vote
1answer
76 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 ...
1
vote
1answer
102 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, ...