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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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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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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660 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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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
303 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
5k 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
50 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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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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453 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
357 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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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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728 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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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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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
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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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98 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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796 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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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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692 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
92 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
455 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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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
230 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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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
39k 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
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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
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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
365 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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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
451 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
173 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
373 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 ...
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1answer
698 views

Why don't ions have one equilibrium potential? (Nernst equation)

I know that equilibrium potentials are dependent on the ratio of ion concentrations inside and outside of the cell and temperature. I also know that the equilibrium potential is reached when there is ...
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1answer
715 views

Why does the potential difference of a current drop, when silver nitrate is added to deionised water?

Semi-related to Why do some salt ions in solution conduct electricity better than others? After conducting more experiments, using deionised water as an analyte only, I found the potential difference ...
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1answer
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Why are potentials of cells with magnesium electrode always lower than expected?

I have prepared the 1M water solution of magnesium acetate. Then I placed $\ce{Mg}$ and $\ce{Cu}$ electrodes in it. I predict there such reactions take place: $$\ce{Mg-2e^- \rightarrow Mg^{2+}}$$ $$\...
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986 views

Concentration of hydrochloric acid for electrolysis?

How much hydrochloric acid (maximum) should I use to do electrolysis of water, and how much amount of voltage should I use to get the maximum of hydrogen and oxygen?
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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
1k views

The anode and cathode when corrosion happens

Let's say $\ce{Fe}$ reacts with $\ce{Cu^{2+}}$ ions. $\ce{Fe}$ would oxidize and therefore give electrons to $\ce{Cu^{2+}}$so that: $$\ce{Fe-> Fe^{2+} +2e-}$$ $$\ce{Cu^{2+} +2e^- ->Cu}$$ The ...
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Preparing CdSe electrodeposition bath

What is the best way of preparing an aqueous solution containing 5 mM $\ce{CdSO4}$, 1 mM $\ce{SeO2}$, 0.5 M $\ce{Na2SO4}$ and adjusting pH to 3 by adding 0.5 M $\ce{H2SO4}$? What is the ...
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Why do Electrons leave the Zinc in a Galvanic Cell

What induces electrons to leave the atoms around the part of the zinc metal in a solution to travel up along that zinc metal and above the solution, through the wire and to the copper metal and ...
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2answers
6k views

Reviving a 6 Volt lead-sulfuric acid battery

I have a 6 Volt sulfuric acid battery used to power a golf cart that has all the acid drained out, and the usual solution was to add more water to the battery however I am afraid that would not work ...
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1answer
74 views

Electrode for methanol

Could you advice an electrode for electrophoretic deposition in methanol which won't spoil methanol and also wont be spoiled by methanol. I googled a bit and found that 1 copper, platinum and gold are ...
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1answer
187 views

Sacrificial Anodes and Pit Corrosion

I have a slab of aluminum and one part of the slab will be exposed to a very corrosive environment. If I put a sacrificial anode elsewhere on the slab will the section that is exposed still be ...
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2answers
1k 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 ...
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1answer
113 views

Can we make a rusting battery

Since in rusting (oxidation) of Iron, transfer of 4 electrons takes place is it possible to use this reaction under catalytic conditions to create a simple electric cell, even if it just gave a ...