What is Electrochemistry: Definition and 105 Discussions

Electrochemistry is the branch of physical chemistry concerned with the relationship between electrical potential, as a measurable and quantitative phenomenon, and identifiable chemical change, with either electrical potential as an outcome of a particular chemical change, or vice versa. These reactions involve electrons moving between electrodes via an electronically-conducting phase (typically, but not necessarily, an external electrical circuit such as in electrolessplating), separated by an ionically-conducting and electronically insulating electrolyte (or ionic species in a solution).
When a chemical reaction is effected by a potential difference, as in electrolysis, or if electrical potential results from a chemical reaction as in a battery or fuel cell, it is called an electrochemical reaction. Unlike chemical reactions, in electrochemical reactions electrons (and necessarily resulting ions), are not transferred directly between molecules, but via the aforementioned electronically- and ionically-conducting circuits, respectively. This phenomenon is what distinguishes an electrochemical reaction from a chemical reaction.

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  1. A

    Compare the conductance of an insoluble salt with soluble one

    Options (a) and (b) are facts and therefore correct. Since ionic bonds weaken with temperature, ionic mobilities should increase with temperature. Also in physics, we learnt that the resistance of every material other than conductors (i.e. semi-conductors, insulators and electrolytes decreases...
  2. M

    Voltaic cell + battery in series

    Hello, I wanted to know if connecting a battery in series with a voltaic cell would increase the rate of the redox reactions. Let's take the simplest example of a voltaic cell constituted by a Zn/Zn2+ half-cell connected to a Cu/Cu2+ half-cell. When the circuit is closed, the Zn electrode will...
  3. JulesP

    Lead Acid Battery Flyback Pulses: Electrolyte Decomposition

    Can inductively generated flyback pulses (~1kV) cause the decomposition or ‘consumption’ of any components in the electrolyte of a lead acid battery resulting in an energy release?
  4. Dario56

    Standard Activity in Electrochemistry

    In the textbook Electrochemical Systems by Newman and Alyea, chapter 14: The definition of some thermodynamic functions, chemical potential of component (ionic or neutral) is written as a function of absolute activity: $$ \mu_i = RTln(\lambda_i) \tag {1} $$ where ##\lambda_i## is the absolute...
  5. Dario56

    Diffusion, Migration and Einstein Equation

    In the textbook: Electrochemical Systems by Newman and Alyea, 3rd edition, chapter 11.9: Moderately Dilute Solutions, equation for the mole flux of the component ##i## is given by: $$ N_i = - \frac {u_i c_i} {z_i F} \nabla \bar\mu_i\ + c_i v \tag {1}$$ where ##u_i## is the ionic mobility...
  6. V

    What's the chemistry behind a semiconductor?

    This is a confusing subject for me. It's like only getting half of the story. Reading physics but not understanding how it works in chemistry makes it nonsense to me. Imagine we are creating a silicon-based semiconductor. They have covalent bonds between them, with each silicon atom having four...
  7. Dishsoap

    Chemistry Question about the Butler-Volmer equation in electrochemistry

    I am reading Bard & Faulkner, who states that the current given by the Butler-Volmer equation is related to the overpotential ##\eta##, which is the ##\eta=E_{app}-E^0-E_{eq}##. The equilibrium potential depends strongly on the initial bulk concentration of products and reactants...
  8. kma

    I What happens to resistance of tap water as voltage is increased?

    1 In recent days I have done a few experiments measuring the current of water as it goes up from 9 volts up to 36 volts, and following Ohms law to convert it to resistance. And I discovered a very interesting trend. In between 9 and 18 volts, there is a massive drop in resistance (by around a...
  9. yucheng

    Chemistry Confused with Galvanic Cell concept

    I was watching this video that I found on Youtube. My question is, does type of electrolyte affect the voltage reading, since it dictates which redox reactions are possible? (here, Na2SO4 instread of CuSO4) Consider a Mg|Cu electrode pair in a galvanic cell; the reaction is, usually in...
  10. BenDover

    Aluminum mystery -- Questions about elecrolysis in water

    Hello, human people's. I noticed a strange phenomenon while playing electrochemistry. - i used 2 strips of aluminum foil as electrodes in sodium sulfate solution, 1 for positive terminal and other for negative. Applied 5 volts, essentially zero current flew. - i used 1 strip aluminum for...
  11. Dario56

    Definition of Absolute Electrode Potential

    Hey guys, I have two questions: 1) I thought absolute electrode potential is galvani potential difference at the interface. However, it is given by this equation in John Bockris - Modern Electrochemistry: $$ E(abs) = ^M\Delta^S\phi - \mu_e^M/F $$ First term is galvani potential difference on...
  12. Dario56

    Understanding the Role of a Voltmeter in Electrode Potential Measurement

    Voltmeter is an instrument which measures electric potential difference between two points. When measuring electrode potential of some redox system (vs SHE for example), it is said that voltmeter reading contains sum of all potential differences present in a cell. This includes all...
  13. Dario56

    Internal Resistance of the Battery - Ohmic Resistance

    When current starts flowing in a circuit, voltage of the battery drops from EMF value. There are three sources of this however here I am only interested in ohmic resistance of the battery. EMF of the battery is created because of electrochemical processes on both electrodes which create...
  14. Dario56

    Entropy Changes in Electrolytic/Galvanic Cell?

    One of the most fundamental equations in chemical thermodynamics states: $$ \Delta_rH_m^⦵ = \Delta_rG_m^⦵ + T \Delta_rS_m^⦵ $$ If we look at this equation in context of net chemical reaction in electrolytic or galvanic cell, it is usually interpreted as follows: Enthalpy of reaction denotes...
  15. Rzbs

    Lithium-ion rechargeable batteries

    I want to know how a lithium ion rechargeable cell works with very basics details. I don't need a simple describtion like most of the websites and videos. I need a resource that explain the chemistry and physics of a Li ion cell from very basics of knowledge. Could you please introduce such a...
  16. MarcoUscanga01

    Query on electrochemistry: Vectorial charge transfer meaning

    Hello guys! When talking about electrochemistry what is the difference between saying "electron transfer" and "vectorial electron transfer". It seems to me that "vectorial electron transfer" is just another fancy way of saying "electron transfer" but I am not quite sure if there is a kind of...
  17. E

    Clarification about the sign of EMF in batteries and electrochemistry

    In electrochemistry, we define ##E_{cell} = E_{cat} - E_{an}##, the difference between the electrode potentials of the cathode and the anode. This has the effect that if the reaction is spontaneous, we obtain a positive ##E_{cell}## and if it is not - i.e. we need an external driving voltage...
  18. J

    Exploring Anodic & Cathodic Tafel Curves: Uneven Electrodeposition?

    The shapes of the anodic and cathodic Tafel curves are different. What does it mean? Does it mean that the electrodeposition of the copper onto a surface of an electrode is uneven? If yes, I am also thinking that this has something to do with the macrothrowing power? Since it was done in an...
  19. R

    Experimental method question - electrochemistry

    I am looking at a paper (ref below) that uses a method to precipitate calcium carbonate on a steel pipe. However, the paper gives no method because the reference it uses is linked to a thesis that has not been released. The setup is below... Now, I kind of understand that it uses a method of...
  20. D

    Electrochemistry and cell electroplating

    Hello, I have a question in regards to electroplating. If i have a cell with let's say a zinc cathode and an inert anode in a solution of copper ions, and I turn on the current, what reaction will counter the reduction of copper ions to balance the electronegativity and what will be the...
  21. C

    Redox Flow Battery Charging: Understand Electrochemistry

    I am researching the electrochemistry of redox flow batteries, however, I do not understand the charging process. As I understand DC current arrives in an electrode and transfers energy to excite electrons in the electrolyte thus providing energy to trigger a chemical reaction (storing...
  22. cianfa72

    Voltaic Cell behaviour as described in this video

    Hi, googling for Voltaic cell I found this video about it. At minute 2:35 to 2:54 you can see that, without any electrical conductor connected between electrodes, in the Copper half-cell the metal electrode (Cathode) gets an amount of negative charges (electrons). Basically what described there...
  23. cianfa72

    Daniell cell initial equilibrium

    Hello, consider again a simple Daniell cell with salt bridge in place but no external electric connection between electrodes. Reading from some source e.g. link1 it seems upon Zinc and Copper metal rods are dipped into their own ions solution, both will gain a negative charge (-) due to an...
  24. cianfa72

    Galvanic cell - open circuit voltage and EMF

    Hi, having not a deep knowledge of electrochemistry I've some doubts about processes involved in a galvanic cell. Take for instance a Zn/Cu Daniell cell for which E0cell is 1,10V. That means emf for it is 1,10V. Starting to read from how battery works I had a first understanding of how...
  25. L

    Electrolysis of NaHCO3 solution with lead electrodes

    Hey. If i carry out electrolysis of saturated sodium bicarbonate solution with lead electrodes, will the lead electrodes will dissolve to form lead carbonate (or basic lead carbonate if temperature is higher) or the lead ions will migrate from anode to cathode and deposite there? I think that...
  26. Dor

    I What should be continuous at the interface of two materials?

    At the interface between: 1) conductor/conductor 2) conductor/semiconductor (or dielectric) 3) semiconductor/semiconductor (or dielectric/dielectric) What quantity should be continuous? Is it the electrochemical potential, only the chemical potential or is it the electric potential? Since they...
  27. S

    Calculating the conductivity of a solution of HCl and HAc

    Homework Statement I need to calculate the specific conductivity k and the resistance R of a cell containitng 0.01 M HCl and 0.1 M acetic acid (HAc). I know the molar conductivity of HAc: Λm = k/c = 5.14 cm2S/mol. I also know Ka (HAc) = 1.795 *10-5. I know the cell constant Kcell = R*k =...
  28. E

    Which reference electrode to select?

    Hi. Is there any significant difference in quality and accuracy between reference electrode with Vycor frit (porous glass attached with heat-shrink tube) and the one equipped with ceramic frit (molten in the glass tube) like in this example...
  29. R

    Is a gold electrode supposed to corrode during electrolysis?

    Help! I was under the assumption that a gold electrode for oxygen would be able to sustain water electrolysis with sodium bicarbonate as the electrolyte without degrading, so I bought a foot long of 28 gauge 24k(pure gold) wire, but I've been putting it to the test for about 30 minutes and it's...
  30. M

    Can rechargable Li-ion batteries be rebuilt?

    After so many cycles, rechargeable Li-ion batteries powering electric cars go bad. This I know. I am wondering what goes bad? Is it the electrolyte, the electrodes, or both? And in general, could it be possible to take these degraded battery components and fix them? Thanks in Advance! Mike
  31. T

    Electrochemical overpotentials (V3+/V4+ redox)

    Hey, Does anyone know a good source for overpotentials on carbon / graphite electrodes? Especially looking data for V4+ + 2H+ + e- <-> V3+ + H2O (+0.34V vs. SHE) overpotential. Or are there any ways to estimate the overpotentials? Thanks
  32. T

    Understanding Electrochemistry: Anode and Cathode Reactions

    Hi All, I have a quick - probably quite basic - electrochemistry query I hope you can help with... I have an anode and a cathode separated by water with current flowing between. There is some oxygen dissolved in the water so the reaction O2 + 2H20 + 4e -> 4OH occurs. Electrons flow out of the...
  33. M

    Electrochemistry: rate constant dependence on CV peak

    Hi there, I am currently studying charge transfer reactions between metallic electrodes and redox couples in aqueous electrolytes (in a diffusion limited system), and I was wondering about the influence of the rate constant on the reduction/oxidation peak maximum. Typically, it is assumed that...
  34. Eureka99

    Understanding Equilibrium in Electrochemical Reactions

    Hi everybody! While I was studying the Pourbaix diagram of chlorine ( and its disproportionation), I got stuck in a conceptual problem about the potential E. The diagram, as I understood, it's supposed to represent the equilibrium between the various species, but knowing that at equilibrium the...
  35. F

    Electrochemistry : characterizing the electrode-electrolyte

    Hello guys (and gals), I have mostly a background in Physics, but I've recently had to get some knowledge on electrochemistry, and more precisely on electrode-electrolyte interface. From "Modern Electrochemistry 2A : Fundamentals of Electrodics" by Bockris I gathered that in the case of a...
  36. S

    Electroplating Cu on Cu sputtered Si Substrate (Lithography)

    I have been trying to plate Copper on Copper sputtered Electronic grade Silicon Substrate which has been patterned and developed using UV photolithography. The patterns measure about 50-100microns in width and are about 1600microns long. I have tried plating 10micrometer thick Cu using a stock...
  37. T

    Copper Electroplating, cell voltage = 0V?

    Hello everybody, this is probably a very novice question, but imagine anode and cathode, both made from copper immersed in CuSO4 aqueous solution (1M at standard temp and pressure + assuming electrodes are very near each other -> minimizing diffusion/migration resistance) and: Cu(2+) + 2e- ->...
  38. R

    Electrochemistry question: n value in ΔG° =-nFE°cell

    If I want to find the standard ΔG for a reaction in an electrochemical cell, I can use the equation ΔG° =-nFE° where n is the number of moles transferred, F is Faraday's constant, and E° is the standard emf of the cell. If I know the standard reduction potentials of the redox reactions happening...
  39. Etienne

    Electrochemistry Question -- Which cell reaction will proceed toward the formation of more products

    Homework Statement The E° value of one cell reaction is positive and that of another cell reaction is negative. Which cell reaction will proceed toward the formation of more products at equilibrium? *Problem 19.20, Chemistry: Chang, Raymond. 10th ed. Homework Equations E° cell = E° cathode -...
  40. A

    The Nernst Equation- I apologize in advance for my ignorance

    Ecell = E0cell - (RT/nF)lnQ So I understand the Nernst Equation, but I don't have some info. (Please bare with me, I'm in secondary) I'm doing a Cu - Al cell. My E cell is negative (-1.33). Does this have an affect on the equation? What exactly does E0 stand for? I understand how to find E...
  41. D

    Find Cell Potential Given Mass

    Homework Statement Consider the following half reactions at 298 K Ni2+ + 2 e- → Ni Eo = -0.231 V Pb2+ + 2 e- → Pb Eo = -0.133 V A galvanic cell based on these half reactions is set up under standard conditions where each solution is 1.00 L and each electrode weighs exactly 100.0 g. What will...
  42. ZetaOfThree

    Need to learn some electrochemistry fast

    I am an undergraduate who recently started on a research project involving the dielectric properties of colloidal suspensions. Though my physics background is strong, my chemistry background is weak and I would like to learn about the following concepts relevant to my research: 1. Electrode...
  43. S

    Why do electrons move away from the electrode in a galvanic half-cell?

    In a standard galvanic half-cell when Zinc rode is placed into the Zinc sulphate. What is the reaction which makes zinc to dissolve and fell into the solution. Why do electrons move away from the sides of the electrode? Are they repelled by the solution or by other ZN atoms on the electrode...
  44. I

    Electrochemistry - Voltaic Cell

    A voltaic electrochemical cell consists of a silver electrode in contact with 200 mL of 0.1 M AgNO3 and a magnesium electrode in contact with 300 mL of a 0.1 M Mg(NO3)2 solution. We have the following data: Ag+ + e- --> Ag (E° = 0.8 V) Mg2+ + 2e- --> Mg (E° = -2.372 v) a) Calculate the value of...
  45. T

    Understanding Three Electrode System Interactions

    Hello, I have two doubts. In a three electrode system, do the reference electrode and the auxiliary electrode interact (by direct contact or other way) with the analyte? And why? The second doubt consists in this point and I think is connected to half of the previous question: during for...
  46. AdityaDev

    Electrochemistry: reference electrode

    Reduction half reaction : Cu2++2e- -> Cu(s) I have a doubt in using the reference electrode. For example if I have the calomel electrode (ESCE=0.24V) how do I use it with the copper half cell? Are these reactions correct? Cu2++2e- -> Cu(s) 2Hg+2Cl -> Hg2Cl2+2e- To get Ecell=0.24+ECu|Cu2+
  47. Y

    Electrochemistry pH in solution cell

    Hello Forum :), Please find attached my problem. The solutions is also there. BUT, I do not understand why my teacher does not simply assume pH=0. It seems as though we are using the standard hydrogen electrode (ie 1M H+ in solution!).
  48. U

    Calculating Volume of Water in a Swimming Pool Using Conductivity Measurements

    Homework Statement A sample of water from a large swimming pool has a resistance of 10000Ω at 25C when placed in a certain conductance cell. When filled with 0.02M KCl solution, the cell has a resistance of 100Ω at 25C. 585gm of NaCl were dissolved in the pool, which was thoroughly stirred. A...
  49. W

    Electrochemistry Reference Electrodes

    Homework Statement Change your electric potential readings from a Ag/AgCl system to a RHE (reversible hydrogen electrode) system at pH 7. For example, 0.3 V vs Ag/AgCl and -0.1 V vs Ag/AgCl Homework Equations Ag/AgCl 0.222 Volts RHE 0 - 0.0591*pH Volts The...