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).

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8
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1answer
615 views

How do I determine whether it is the *ferrous* or *ferric* ion that is implied in this displacement reaction?

I'm supposed to write a balanced equation for: $$\ce{Iron(s) + copper(II) sulfate(aq) -> ?}$$ If I use Iron(II)/ferrous I get $$\ce{Fe + CuSO4 -> FeSO4 + Cu}$$ and if I use Iron(III)/ferric, ...
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1answer
185 views

Fundamentals of Li-ion Functionality

I would like to have an in-depth understanding of Li-ion batteries functionality, at atomic level. Can anyone help me to understand it? I have included some known background to support my questions. ...
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1answer
4k views

Why can't a galvanic cell be a single cell?

I get that galvanic cells require a salt bridge to maintain neutrality so the cathode doesn't become saturated with electrons, but why is a two-cell setup required? Wouldn't the spontaneous reaction ...
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2answers
453 views

Still taught to reverse oxidation half cells in electrochemistry?

In a question, Oxidation of metals/halogens by oxygen gas in acidic aqueous solution, there was a point made that reduction half-cells should not be reversed. I was taught ($\approx 1970$) in the ...
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3answers
11k 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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1answer
2k views

Delta G for Standard Hydrogen Electrode reaction

I’m dealing with electrochemistry problems. For the following reaction $$\ce{2H+ +2e- <=>H2}\quad E^\circ=0\ \mathrm{V}$$ Does it make sense to say $$\Delta G^\circ=-nFE^\circ=0$$ Which would ...
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1answer
2k views

How can I produce hydrogen gas efficiently and cheaply?

I have been intrigued by one of the principles of chemistry lately- electrolysis. In my knowledge, electrolysis is a quite dangerous operation as the decomposition of water produces hydrogen and ...
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2answers
10k 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 ...
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1answer
777 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 ...
3
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2answers
440 views

Is it possible to have electric field in water without having electrolysis?

Is it possible to have electric field in water (using electrodes with voltage difference) without having electrolysis in the water (or any other reaction)?
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2answers
162 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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3answers
5k views

Is it dangerous to inhale the steam coming from electrolysis of salt-water solution [closed]

Is chlorine in there that accumulates (at the anode) and emerge out as chlorine gas? I was worried since I added a pinch of salt to the steamer in order to hasten the heating of tap water when I ...
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1answer
7k views

Reaction of sulfate ion in copper sulfate electrolysis

I am planning to try copper plating a piece of metal by performing electrolysis on an aqueous solution of copper sulfate. I plan run an electrical current with the metal I want to plate as the cathode ...
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2answers
1k views

Why does copper form bubbles in vinegar in this situation?

I watched this video in which the host tries to show the principles behind the voltaic pile. The host first immersed zinc in vinegar and bubbles are observed forming around zinc. I've learned that ...
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3answers
6k views

Hydrogen fuel cell - why do the H+ ions move through the electrolyte

Consider the following hydrogen fuel cell http://butane.chem.uiuc.edu/pshapley/Enlist/Labs/FuelCellLab/FuelCell.html At the anode, hydrogen is oxidised (losing electrons). My first question is this: ...
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Effect of concentration on molar conductance

It has been stated that the molar conductance($\Lambda_m$) of strong electrolytes is not affected to a greater extent on dilution and so to find the limiting value of molar concentration($\Lambda_m^0$)...
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1answer
2k views

While electrolyzing concentrated aqueous sodium chloride, why is it that chlorine is discharged but not sodium?

Hydrogen and hydroxide both exceed sodium and chlorine in terms of reduction and oxidation potential respectively. While electrolyzing a concentrated solution of aqueous NaCl, it is known that ...
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1answer
342 views

Why the reduction potential of the reaction AgCl (aq) /Ag + Cl- is +0.22V

The point is $\ce{AgCl_{(aq)}}$ is the same as $\ce{Ag+}$ + $\ce{Cl-}$ (again, in water) So my reduction reaction would be $$\ce{Ag+ + Cl- + e- -> Ag + Cl-}$$ then the equation is simplified by ...
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2answers
816 views

How is the standard electrode potential measured without allowing the electrolyte concentrations to change?

Let's say we need to measure the standard electrode potential of a zinc electrode dipped in an aqueous solution of $\ce{ZnSO4}$. To do this, we use the standard hydrogen electrode(SHE)-the reference ...
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1answer
4k views

What is the Purpose of an Electrolyte in a Galvanic Cell?

I understand how a galvanic cell works and the purpose of erverything such as the ssalt bridge and the electrodes, however I don't understand why an electrolyte is required. For example, consider this ...
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2answers
4k views

In practice, do polar molecules actually align in an electric field?

We have all seen the following diagram (or similar) in our first chemistry class, depicting polar molecules aligned in an electric field. Is this just one of the half-truths of beginner chemistry or ...
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1answer
251 views

Can I use one alkaline battery to recharge another?

Unfortunately, I don't have batteries to waste to test this myself, but I am curious... Let's say you have two identical batteries. AA Duracell. Now let's say you run one of the batteries through ...
8
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1answer
376 views

Is this product description wrong and a simple battery and not a fuel cell?

I won this "toy" at a science fair... Now I have to make a short presentation about it in school. On the package description they describe its energy source as "fuel cell"... It consists out of a ...
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2answers
15k views

How to determine the value for n in the Gibbs free energy and redox potential equation?

I am having a problem with this equation for redox potentials $$\Delta G = -nFE_\mathrm{cell}$$ In this equation I never am totally sure about what the value of $n$ should be, for example for the ...
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1answer
3k views

Would an amalgam filling under or next to a gold crown cause any electrochemical reaction?

Would a mercury amalgam filling deteriorate faster if it was in contact with a gold crown?
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519 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 ...
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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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2answers
10k 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 ...
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1answer
2k views

What are possible side reactions for the generation of hydrogen via electrolysis?

I recently completed making a simple water electrolysis setup to generate hydrogen which uses two graphite rods from a standard AA battery. The power source is a $24~\mathrm{V}$ $6~\mathrm{A}$ adapter....
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1answer
102 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 ...
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2answers
186 views

Oxidation of metals/halogens by oxygen gas in acidic aqueous solution

I had some confusion about the correct answer to the following question: Which substance can be oxidized by $\ce{O2(g)}$ in acidic aqueous solution? Two of the answer choices were metal cations (...
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1answer
8k views

how is the relation between Gibbs free energy and cell potential?

First of all what is exactly Gibbs free energy in regards to an electrochemical process? How can we visualise it? How does Gibbs free energy change in an electrochemical reaction? How is it related to ...
2
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1answer
332 views

Voltaic and electrolytic cells

Why more attractive metals will be oxidized? Aren't they being reduced, because they attract and receive electrons from negative polyatomic ions? So they will be anodes, where oxidization occurs. Why ...
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1answer
2k 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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1answer
424 views

During electrolysis, why are the products attracted to the cathode?

Take the electrolysis of Lead(II) bromide: We can write it as two half-reactions: $$\ce{Pb^{2+}(l) + 2e^{-} \rightarrow Pb(l)}$$ $$\ce{Br^{-} \rightarrow Br + e^{-}}$$ In the electrolysis reaction,...
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4answers
395 views

In NaCl electrolysis, why does chlorine ion get oxidized but not oxygen ion? [closed]

In $\ce{NaCl}$ electrolysis, on the positive electrode (aka. on the electrode where oxidation happens), $\ce{Cl-}$ ions were oxidized to $\ce{Cl2}$. But we don't see any $\ce{O^2-}$ at all. My pre-...
2
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1answer
198 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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1answer
645 views

Redox Mg+Copper(II)

If I put solid magnesium in a solution of Copper(II) sulfate, what reaction occurs that causes the bubbles? Looking at the Potential tables the only reaction that theoretically occurs is the ...
2
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1answer
939 views

Why do some salt ions in solution conduct electricity better than others?

My experiment involves a potentiometric titration, and I have used $\ce{AgNO3}$ as a titrant and KCl/KI/deionised water only as an analyte. In the image below of my data, the potential difference as ...
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1answer
59 views

Is this galvanic cell representation right?

Question 13. In the galvanic cell: $$\ce{Pt(s) | I2(g) | I-(aq) || Fe^3+(aq) | Fe^2+(aq) | Pt(s)}$$ Representation of anode is incorrect and cell will not work. $[\ce{Fe^3+}] = [\ce{Fe^2+}] = [\ce{I-...
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1answer
658 views

Where does the charge on an electrode, responsible for the formation of a double layer once submerged in an electrolyte, come from?

I've started exploring electrical double layers and electrode-tissue interfaces whilst dealing with deep brain stimulation and stimulus artefact. I've heard many times that what causes the double ...
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1answer
142 views

Why does increasing the concentration of the salt bridge in a galvanic/voltaic cell increase voltage?

I recently set up an experiment with 1M half cells made up of zinc and copper nitrate. They were connected with a sodium nitrate salt bridge of varying concentrations. As the concentration doubled 5 ...
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1answer
1k views

How to calculate galvanic cell spontaneity?

I was wondering how to calculate cell spontaneity for a galvanic cell. Do you just look up the enthalpy values of electrode reactions? Does the electrolyte solution you choose have an effect on cell ...
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0answers
1k views

Why do the Metal Ions in an Electrochemical Cell Not Pass Through a Salt Bridge?

I understand that the purpose of a salt bridge is to maintain the neutrality of the solutions in an electrochemical cell, but why do the ions being oxidized and reduced not pass through the salt ...
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1answer
57 views

Wattage to produce 6L of air from Water in less than a second?

So I understand the question is probably vague to a scientist, but this is all the specifics I could mustard up with my non-scientific background. So I understand the basics of the process and have ...
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1answer
837 views

Why would electrode reaction in galvanic cell stop when there's no neutrality in each cell?

I know that the salt bridge produces ions to balance out the positive and negative ions in each solution, but why won't it work without a salt bride? Would it even work at the start since there's few ...
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1answer
510 views

electrochemical (Galvanic) cell solution purpose [closed]

I will try to rephrase my confusion: I am not sure if the redox reactions occur in Galvanic cell because of the wire connecting the 2 metals or because of the solution causing electrons to leave the ...

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