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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2answers
9k 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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2answers
5k 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?
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How to calculate the potential via Hess's law? Is my textbook wrong about this?

It is my understanding that to apply Hess' Law to this equation the top equation sign would be reversed and the outcome would be +0.65 V. Often the system produces incorrect answers. I was looking ...
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1answer
232 views

How does an electrolyte react to voltages below its electrolysis potential?

An electrolyte can be electrolysed by a voltage higher than the reverse reaction’s cell potential, while conducting a current in the process. But what happens at the electrodes when the applied ...
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1answer
52 views

Electrodeposition of Ni

How can one electrodeposit Nickel on a substrate using a liquid crystal template? substrate is Indium Tin Oxide coated plate and the template is cetyl trimethylammonium bromide(CTAB)+WATER+ETHANOL
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1answer
9k views

Standard electrode potential of a galvanic half cell is zero at equilibrium at standard conditions?

At standard conditions(at 1atm pressure and unit activity(1molal or 1molar concentration)of all dissolved compounds),the electrode potential is equal to the standard electrode potential by the Nernst ...
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1answer
497 views

Plotting ΔG vs Temp for Electrochemical Reaction

I’m doing an electrochemistry lab that requires me to construct various galvanic cells in an attempt to solve for $\Delta H$, $\Delta G$, and $\Delta S$ values of an unknown. During one part of the ...
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204 views

Finding one of the two unknown potentials with a given voltage of a net reaction

A half-cell consisting of palladium rod dipping into a $1\ M$ $\ce{Pd(NO_3)_2}$ solution is connected with a standard hydrogen half-cell. The cell voltage is $0.99\ volt$ and the platinum electrode in ...
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1answer
191 views

Electrochemistry - Redox & Electroplating

I've stumbled across a problem that I need help on, it is mostly Electrochemistry and I will show my work. Line Notation Error: $$\ce{Fe~|~Fe^{+2}~||~Cl^{-},Cl2~|~Pt}$$ After that, I ...
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86 views

Basis set in the computational software “Gaussian-03” for studying adsorption of a hydrogen atom on a carbon paste electrode dropcasted with Pt-CNT

What is the basis set in the computational software "Gaussian-03" that can be used to study the interaction of $\ce{H}$-atom with $\ce{Pt-CNT}$ dropcasted electrode? How can we study the energy ...
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1answer
71 views

An electric potential is generated when a liquid moves with respect to a solid (streaming potential). Is the reverse true?

Streaming potential is an electrochemical phenomenon that a that relates electric currents with the relative movement of solid and liquid phases in contact with each other. So when a liquid moves ...
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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

Does the relationship equation between standard cell potential and equilibrium constant violate potential's intensive properties?

The equation: $$E^{。}_{cell}= \frac{RT}{nF}\ln K_{eq}$$ We all know cell potential is intensive, not affected by the amount, Because: $volt=\frac{joule}{coulomb}$. Both joule and coulomb will be ...
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2answers
94 views

Transistors: How does the gate work?

Two questions: First, how does the gate provide a positive charge by running a current through it? I really just don't see how this positive charge could be achieved, unless you had some sort of ...
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1answer
1k views

Accelerated Oxidation Of Iron When Coating Breaks

I was presented with the following information: If iron is painted, then oxygen and water are prevented from contacting the metal, and corrosion is avoided. Sometimes the iron is coated with a thin ...
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2answers
602 views

How is a car battery recharged?

When recharging a lead-acid battery, how are the terminals of the battery connected to the voltage source. I mean, do we connect the positive terminal of the battery to the negative terminal of the ...
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2answers
2k views

What's the source of electrical energy in galvanic cells?

Let's take a simple Daniell cell for example: Where does the energy required to drive electrons through the external circuit and power up devices (like a light bulb) come from? Does the oxidation of ...
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1answer
298 views

Ionize Hydrogen and Oxygen Gas in Electrolytic Cell?

As is well known, water can be electrolyzed into oxygen and hydrogen gasses. However, all redox reactions can be run in reverse. If I were to electrolyze water in 2 closed containers (in order to trap ...
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1answer
4k views

Electroplating a spoon (electrolytic cell) using a electrochemical voltaic cell

I drew a rough picture of the two cells, and marked each position with a distinct letter: The whole reason I am asking this question is that I am bit confused and unsure about some of the chemistry ...
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1answer
47 views

Why is the deposition of silver more uniform from [Ag(Cl)₂]⁻ (aq) than from Ag⁺?

What determines the uniformity? Just a fun fact I am wondering about, because I saw cyanide solutions used in electroplating.
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1answer
1k views

in the electrolysis of H₂SO₄ solution, when the concentration is increased why does the current increase even when OH⁻ ions reduce?

During the electrolysis of $\ce{H2SO4}$, $\ce {OH-}$ ions are more reactive than $\ce {SO4^{2-} }$ ions and so they dissociate. as $\ce {OH-}$ ions dissociate, they are the negative ions that carry ...
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1answer
3k views

Electrical conductivity of pool water

What is the electrical conductivity of pool water? I tried to find some information, unfortunately with no success. I need to know it to make an underwater electronic project. Thanks
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431 views

Hydrogen Fuel Cell and Battery

For hydrogen fuel cell to produce electricity, hydrogen will need to be supplied to the anode. To split oxygen and hydrogen from water and obtain hydrogen, we need to use electrolysis. To use ...
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1answer
338 views

How can I make a graphene supercapacitor?

I have heard that a super capacitor can be made with a dvd burner. What materials do I need to to get and what software for my DVD burner do I need to make this amazing device?
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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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712 views

Concentration cell lower half cell concentration from measured cell potential

I am trying to find the Ksp of silver thiocyanate: AgSCN(s) --> Ag+ (aq)SCN-(aq) but I need to first prove that the lower [Ag+] = 1.27-12 M, but don't know how to find it. The data I am given: ...
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1answer
82 views

What's a good resource/book on pH measurements?

Most resources on pH and the electrochemistry behind it that I've found are IMHO too superficial. For example, they explain that an electrode with less than 80% slope should be discarded, but not why ...
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5answers
2k views

Electrolysis of Water

What is the mechanism for the electrolysis of water? I understand that hydrogen and oxygen gas are made, but how exactly does this happen when electrons are passed through water? A diagram would be ...
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2answers
26k 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 ...
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1answer
2k views

Anode and Cathode Understanding

I am very much confused: in the cell (Zn, Cu in $\ce {H2SO4}$), Cu is positively charged and is anode, where in this cell (Zn in $\ce {ZnSO4}$ and Cu in $\ce {CuSO4}$), Cu is positively charged but is ...
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1answer
97 views

Formation of O₂, Water, and Electricity from Hydroxide?

The Clark Type Oxygen Electrode converts water, oxygen, and electrons into hydroxide via a hydrogen peroxide intermediate: \[\ce{O2 + 4e^{−} + 2 H_2O -> 4 OH^{−}}\] Which is the sum of: \[ \begin{...
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2answers
647 views

Why is water considered ionic in fuel cells but otherwise covalent?

If water, $\ce{H2O}$ is a covalent compound formed by sharing of electrons, why is it said (in case of fuel cells) that formation of water from hydrogen and oxygen is a redox reaction (transfer of ...
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2answers
332 views

Anode and Cathode

I am very much confused: in simple voltaic cell ($\ce{Zn,~Cu}$ in $\ce{H2SO4}$), $\ce{Cu}$ is positively charged and is anode, where in Galvanic cell ($\ce{Zn}$ in $\ce{ZnSO4}$ and $\ce{Cu}$ in $\ce{...
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652 views

Cell overpotential diagrams

Is there anyone who knows a book where I can find a detailed explanation of cell overpotential diagrams, like the ones shown here? Thanks in advance!
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1answer
2k views

Is reduction potential equivalent to the ease of discharge?

Loosely speaking, is the reduction potential equivalent to the ease of discharge in the context of electrolysis? i.e. is it easier to discharge an ion with a higher reduction potential as opposed to ...
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3answers
1k views

Determine if the following change is an oxidation, a reduction, or neither

The following reaction is not a complete reaction. Determine if the change is an oxidation, a reduction, or neither: $$\ce{CrO4^{-2} -> Cr2O7^{-2}}$$ I know that the answer to this problem ...
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1answer
85 views

Reverse electro-plating byproducts

Following this plan, I am wondering what the byproducts of this method are? At the site with the q-tip, the solution turned a bright yellow, with the q-tip turning a dark yellow, almost red. Holding ...
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1answer
449 views

Why don't B, C, Si, have ionic forms?

Also, why can some elements such as $\ce{Fe}$ have different ionic forms such as $\ce{Fe^{2+}}$ and $\ce{Fe^{3+}}$? What determines each form?
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254 views

The feasibility of the electrochemical cell.

This is the question extracted from my country high school level' exam. So it asks to discuss the feasibility of the electrochemical cell to carry out electrolysis of an aqueous solution of sodium ...
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1answer
228 views

offset in measuring decomposition potentials

as far as I've understood to measure the decomposition potential of an electrolyte using a galvanic cell we just put two electrodes, connect them to a battery, and vary the external potential till ...
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1answer
130 views

What happens to the hydroxide anion during the electroreduction of water?

The reduction of water at a cathode is represented by the following equation: Cathode (reduction): $\ce{2 H2O_{(l)} + 2e^{−} → H2_{(g)} + 2 OH^{-}_{(aq)}}$ If this is done in a divided cell, what ...
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2answers
5k views

Electrolysis of molten Calcium Chloride: Identifying the product

I was trying to make Calcium metal by electrolyzing molten $\ce{CaCl_2}$. I used a stainless steel spoon and a thick steel wire as electrodes. Then I attached them to a power supply. I placed some $\...
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1answer
37k 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 ...
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1answer
1k views

Cathodic protection of tubes in Shell & Tube Heat Exchanger

Our $\ce{Cl2}$ liquifier is of the following type: It is entirely made of mild steel (shell as well as tubes plus the connecting pipelines). At shell side there is Freon (R-12) with its refrigeration ...
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1answer
2k views

Oxidization of Copper In Electrolysis

So during school today, I am running an electrolysis experiment with water and sodium bicarbonate copper leads on both the anode and cathode. I am noticing the usual $\ce{NaO}$ on the anode, and $\ce{...
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2answers
346 views

How to use salt spray data in real environments?

I want to convert resultant hours of salt spray corrosion test to estimated values in years for real life environments such as marine. In other words, How could I predict the result of real life tests ...
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67 views

How is streaming potential measured?

This paper describes the measurement of streaming potential using a potential divider configuration. However it is unclear where the potential difference is created. From the diagram it appears that ...
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1answer
426 views

Why is chloridric acid used in salt bridges?

I've been planning an experiment on how to make galvanic cells and during my research I came across an article in which chloridric acid was used, along with a soluble salt and agar-agar, in salt ...
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1answer
153 views

Entropy - Negligible?

In electrochemistry, the Nernst equation tells us the cell potential for non-standard conditions. I read that the factor $\frac{-RT}{nF}\ln{Q}$ accounts for difference in cell potential due to ...
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1answer
371 views

Ion-selective electrodes

Some ion-selective electrodes can be expensive (starting from $500). Is there any relatively inexpensive do-it-yourself alternatives that would still give very accurate results? How does one make an ...