Electrochemistry Definition and 109 Threads

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. 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+
  2. 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!).
  3. 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...
  4. 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...
  5. Hyo X

    Electrochemistry in organic (nonpolar) solvents

    Im not that familiar with electrochemistry. You have some liquid solution with some concentration of ions, a reference electrode and a sacrifical electrode. You apply a potential with some feedback to control the potential environment of the liquid in the cell. Roughly? Can you do this...
  6. D

    Electrochemistry Exercise: Normal Potential of a Reaction

    Homework Statement Calculate the normal potential at 25 °C for the reaction: HA(aq) + e- → A-(aq) + 1/2H2(g) if the dissociation constant of HA is equal to 3.3*10-4 Homework Equations ΔG° = -RTlnK ⇔ -ΔG°/nF = RT/(nF)lnK ⇔ E° = RT/(nF)lnK The Attempt at a Solution Just...
  7. S

    Electrochemistry research project

    Hey guys I need to do a research project in my high school course on factors affecting internal resistance of an electrochemical(primary) cell which i need to make.I need to take an experimental approach and before that , i need to know what are the expected results when i experiment with some...
  8. S

    Corrosion data using Electrochemistry

    Hi, I am a Chemical Engineer but a novice in electrochemistry; hence the query might sound very basic to everyone. We have an industrial electrochemical process (With Iron anode) and we are conducting a lab experiment to understand what is the effect of electrolyte pH on corrosion rate of...
  9. N

    Difference between ionic and molar conductivity ? (Electrochemistry)?

    What I know is Molar conductivity is The conductivity of the elctrolyte divided by its concentration . Can someone please explain the physical significance of this ? Also ionic conductivity depends on concentration, if I dilute the electrolyte the ionic conductivity decreases but Molar...
  10. Q

    Quick question about Electrochemistry anode and cathode

    Homework Statement Pb/Pb2+ and Ag/Ag+ Ni/Ni2+ and Zn/Zn2+ Which one is the anode and cathode? Toward which metal do the electrons flow? The Attempt at a Solution 2Ag2+ + Pb ⇔ 2Ag + Pb2+ Pb is anode and Ag is cathode e- go toward Ag. Zn + Ni2+ ⇔ Zn2+ + Ni Zn is...
  11. Q

    Need help with electrochemistry lab

    Homework Statement Simplified lab procedure: I have 3 wells (from well-plate) one with Cu(NO3)2 and a piece of Cu(s) one with AgNO3 and a small piece of Ag(s) last one with Zn(NO3)2 and a piece of Zn(s) Salt bridges are soaked with KNO3 All of the solutions above have molarity of 0.10M A...
  12. H

    [Electrochemistry] Reduction potential, keq and kd calculations

    Homework Statement A) Calculate the reduction potential for the reduction of E \cdot Fe^{3+} (aq) by Fe^{2+} B)What is the equilibrium expression, equilbrium constant, and K_{d} for E \cdot Fe^{3+} (aq) Known: Fe^{3+} (aq) + e \rightarrow Fe^{2+}(aq) \hspace{15pt} E = 0.22 V E \cdot...
  13. R

    Electrochemistry cathode question

    I am currently looking into photocatalytic materials. Now I might be over simplifying this process but it my observation that I am just looking at electrolysis but instead of electricity provided by a battery I am using electron hole pairs to generate a potential to do my splitting. My question...
  14. AGNuke

    Electrochemistry - Half Cell Reactions

    A Galvanic Cell is given. Write its Anode and Cathode half reactions, complete cell reaction and thus determine if the given is concentration cell. Pt|O_2(1\; atm)|NaO\! H(10^{-3}M)||H_2SO_4(0.5M)|O_2(1\;atm)|Pt I know that at anode, Oxygen will get oxidised, maybe from NaOH solution and...
  15. B

    Electrochemistry and liquid junctions

    I have Pt(s)/H2(g)/HBr(aq)/AgBr(s)/Ag(s) The question asks why a liquid junction is not necessary. So I know AgBr is insoluble in water, and AgBr coats the silver metal. I just don't understand why it does not matter that the Br- anions from AgBr mixing with the H+ cations doesn't necessitate...
  16. K

    Detailed electrochemistry question

    I am a PhD student and I am trying to decipher what is going on in my system, which consists of a platinum electrode, an electrolyte (varying pH, buffer solution with KCl salt and TRIS buffer), thin SiO2 and Si when low bias is applied to the Pt electrode (0 to 0.5 V) with respect to the Si. I'm...
  17. J

    Stuck with a problem in electrochemistry

    Homework Statement A galvanic cell consisting of two silver electrodes,one in a saturated solution of AgBr and the other in a saturated solution of Ag2CrO4 is prepared.Calculate the value of Ecell at 298K Given Ksp(AgBr) = 5x10-13 M2 and Ksp(Ag2CrO4)=2.4x10-12M3 Homework Equations to...
  18. T

    What Is the Potential When Fe^(2+) Changes by .393 M?

    Homework Statement Line Notation Fe | Fe^(2+) (0.587) || Cd^(2+) (1.009) | Cd T = 297 K E(cell standard) = .04 V Find the potential when [Fe^(2+) changes by .393 M Work Cd^(2+) + Fe --> Cd + Fe^(2+) Q = [Fe^(2+)] / [Cd^2+] Q= [.587 + .393] / [1.009-.393] The Attempt at a...
  19. P

    Electrochemistry, emf vs HCL concentration

    Homework Statement I just conducted a lab for pchem where we took electric potential measurements with a volt meter in a solution for the reaction AgCl(s) +1/2 H2 (g) <--> HCl(aq) + Ag(s) We took the measurements using different concentrations of HCl. We were told that the...
  20. B

    What is the reaction at the anode in this electrolysis experiment?

    Hello everyone, I've been reading up on electrochemistry and trying to make the connection from chemistry theory to what I learned during my time as an undergrad and grad student in electrical engineering and I'm having trouble bridging the gap. I have selected one example from my reference text...
  21. R

    Why Does Gas A Exceed Expected Volume in Electrolytic Reactions?

    Hi there, this might be a rather elementary topic but here goes... 1) An electrolytic circuit using graphite electrodes and sulfuric acid as the electrolyte is set up. One of the gases (A) is more than twice the volume of the other (B). Volume of B is taken as 10 cm3. It is found that vol...
  22. K

    Activating the surface in electrochemistry?

    Hi, can someone please tell me what does an expression "to activate the surface" in electrochemistry mean? Brief explanaiton of situation: I am investigating the corrosion resistance of certain metals by means of electrochemical methods. During the grinding of the working electrode...
  23. H

    How Does Electrolysis Affect pH in a HBr Solution?

    Homework Statement A current of 10.7 Amps is applied to a 1.30 L solution of 0.550M HBr converting some of the H+ to H2(g), which bubbles out of solution. What is the PH of the solution after 77 minutes. Homework Equations The Attempt at a Solution (10.7 C/s)(1 mol e/96485 C)(2...
  24. N

    How Do You Balance Oxidation-Reduction Equations in Acidic and Basic Conditions?

    Homework Statement Several problems. 1) Balance these oxidation-reduction equations in both acidic and basic conditions. In each equation, underline the oxidizing agent. (I have highlighted them. Remember, the oxidizing agent is the species that is reduced and gains electrons.)...
  25. A

    Electrochemistry metallurgy mass calculation

    Homework Statement Calculate the minimum mass of carbon needed to reduce 1.00 kg from sufficient zinc oxide. Homework Equations The Attempt at a Solution I think the equation would be 2 ZnO + C = Zn + CO2 I know the molar mass of C is 12.01, O is 16 and Zn is 65.4 I have been...
  26. Z

    Electrochemistry homework help problem

    Homework Statement Tl+/Tl couple can be prepared by saturating 0.100 M KBr with TlBr and alowing Tl+ ions from the insoluble bromide to equilibrate. This couple was observed to have a potential of -0.443V w.r.t Pb2+/Pb couple in which Pb2+ was 1 M. Ksp of TlBr is ? Given: EoPb2+/Pb =...
  27. M

    Electrochemistry Question, Galvanic/Daniel Cell

    Using a very simple set up with high school kids, Zinc Plate *on* Filter paper soaked in ZnSO4 *on* cellophane *on* Filter paper soaked in CuSO4 *on* Copper Plate *in* Petri Dish Copper and zinc plate connected to a speaker. I know the process involved and the equations...
  28. U

    AP Electrochemistry Free Response Questions

    Homework Statement (i) The mass of Fe(s) produced when 1 faraday is used to reduce a solution of FeSO4 is 1.5 times the mass of Fe(s) produced when 1 faraday is used to reduce a solution of FeCl3. Zn + Pb²⁺ (1.0M) --> Zn²⁺ (1.0M) + Pb (ii) The cell that utilitzed the reaction above...
  29. X

    Electrochemistry help, ripples in current effecting reaction?

    I've been messing around with basic electrolysis for the past 3 days making Iron Oxide from nails... So far its instantly successful with a 6v lantern battery, and another combination with 2 9v batteries in series. Well both of those ran dead so my dad let me borrow his 6v/12v battery charger. I...
  30. R

    How to Calculate Ksp for Ag2SO4 Using Electrochemistry?

    Homework Statement An electrochemical cell is made up of a Pb and an Ag electrode: Ag+ + e --> Ag(s) E = 0.8V Pb2+ + 2e --> Pb(s) E = -0.13V Calculate the Ksp for Ag2SO4(s). "Note that to obtain ions in the right compartment, excess silver sulfate solid was addded and a...
  31. C

    Electrochemistry electrode labeling

    well i would like to know how do we label the electrode as negative and positive in a daniel cell. i dnt want the learn course like anode is this and cathode is this but what i want to know as to what's the concept behind that labelling my book says that if the electrode has a positive...
  32. R

    Calc Standard Voltage, Eq Const, & Voltage @ 25°C for Sn + 2Ag+ --> Sn2+ + 2Ag

    Homework Statement Sn + 2 Ag+ --> Sn2+ + 2 Ag a) Calculate the standard voltage of a cell involving the system above. (I got +0.94 Volts). b) What is the equilibrium constant for the system above? (I got 5.71 E 31) c) Calculate the voltage at 25 degrees celsius of a cell involving the system...
  33. D

    ElectroChemistry oxidation-reduction

    How do you know when a species can be oxidized or reduced my an ion? For ex. Which of the species can be oxidized by H+ and which species can be reduced by H2? Ce4+, Ce3+, Fe2+,Fe3+,Fe, Mg2+,Ni2+,Sn
  34. C

    What is the Average Molarity of Sodium Hypochlorite in a Titration Experiment?

    Homework Statement I am required to determine an average molarity for sodium hypochlorite solution, the experiment involved titrating 10 mL of 1:10 diluted bleach (sodium hypochlorite) with sodium thiosulfate, the volumes of titrant used to reach endpoint are, 17.95 mL, 18.31 mL and 18.21 mL...
  35. C

    Solving the Electrochemistry Lab Problem: Determining Na2S2O3 Concentration

    Hello all this is my problem: Homework Statement I have to determine the concentration of a sodium thiosulfate solution used to titrate a potassium iodate solution. The only variable that is known is the concentration of the potassium iodate solution, 0.01 mol/L. There is 20 mL of 0.01 M...
  36. K

    Electrochemistry of galvanic couple in an acidic solution

    Homework Statement From the perspective of corrosion...Gold and Copper II are joined together and immersed in a 1Molar HCl solution. What possible half-cell reactions and full cell reactions can occur? Which one is most likely to proceed?Homework Equations Half-cell potentials for Au^{3+} +...
  37. L

    What Are the Future Applications of Electrolysis in Mining?

    We have been given the task to write a feature article for a magazine such as new scientist on an area of interest within the following fields: -Reduction and oxidation -Electrochemistry -Electrowinning I cannot find anything that interests me and has enough relevant information to start...
  38. G

    Which Electrode is the Cathode in Wade and Tang's Galvanic Cell?

    Homework Statement Two learners, Wade and Tang are working together on a project. They were asked by their teacher to assemble a galvanic cell that would produce a large enough voltage to light up a 1.5V bulb. They are allowed to use two electrodes, one of which must be a zinc electrode...
  39. T

    Electrochemistry (batteries), Wheatstone bridge question.

    Hi, I am using a Wheatstone bridge to measure very low resistances (around 0,2ohms) and my measurements are changing from day to day. If I take the resistance measurement of the same resistor several times, I notice that each measurement will be lower than the next. But the next day, the...
  40. N

    Electrochemistry - Standard Cell Potentials

    Hi, Just having a little trouble understanding the concept of standard cell potential...what is it exactly? I understand that it is compared to a reference potential of 0 for the reaction 2H+ + 2e- -> H2(g). But what does it mean when a given reaction has positive potential (other than the fact...
  41. V

    How Do You Calculate the Redox Potential for This Reaction?

    Homework Statement I have to calculate the redox potential of this equation: Cr2(SO4)3 + 4K2SO4 + 3J2 +7H2O <=> K2Cr2O7 + 6KJ +7H2SO4 I used the nernst equation to calculate the potentials of 2Cr(3+)+7H2O -> Cr2O7(2-) +14H(+) +6e(-) and I2 +2e(-) ->2J(-) which were -1.42V and 0.51V, all...
  42. S

    Electrochemistry: Stability test of reference electrode

    Dear subscribers Re: Stability test of reference electrode One of the important properties of reference electrode is its stability during measurements or potential scan. How one can check its stability in a certain electrochemical system? One of the way is to use internal reference...
  43. J

    Understanding of electrochemistry

    just wondering. i remember once i had a battery, some change, and my keys in my pocket and eventually i reallized the battery got really really hot. just for the heck of it i tried to get that to happen again and it didnt work. can someone explain why this happenned before? i tried putting a...
  44. C

    How to Calculate the Nernst Potential for a Lead Storage Battery?

    Homework Statement For the lead storage battery the overall reaction is: Pb(solid) + PbO2(solid) + 2H+ + 2HSO4- --> 2PbSO4(solid) + 2H2O(liq.) for which standard potential, E°, is 2.04 volts. Calculate E for this battery when the concentration of H2SO4 is 8.1 M, that is both H+ and HSO4- = 8.1...
  45. R

    How Does Electrode Concentration Affect Polarity in a Gold Battery?

    if you make a battery using only au as both cathode and anode and different concentrations(.0001 and 1) of au+, which would be anode and which would be cathode, what would happen? please illustrate. Any help would be highly appreciated Thank you
  46. G

    What Is the Voltage of This Voltaic Cell at 298 K with Given Concentrations?

    Homework Statement Electrochemistry - Nernst Equation Pb2+ + 2 e- → Pb (s) ξo = -0.13 V Ag+ + 1 e- → Ag (s) ξo = 0.80 V What is the voltage, at 298 K, of this voltaic cell starting with the following non-standard concentrations: [Pb2+] (aq) = 0.08 M [Ag+] (aq) = 0.5 M Homework...
  47. A

    Why Does MnO2 Deposit at Positive Potentials in a Three-Electrode System?

    my question is in three electrode system: working electrode, Pt counter electrode, and Ag/AgCl reference electrode. for example, Mn2+ + 2 H2O -MnO2 + 4 H+ + 2 e− ( −1.22 V), the deposition of Mno2 will be accomplished on postive potential. Cr3+ +3e- Cr ( −0.74 V), the depsotion of metallic Cr...
  48. A

    Why Is MnO2 Deposited at Positive Potentials in Electrochemical Reactions?

    Mn2+ + 2 H2O - MnO2 + 4 H+ + 2 e− ( −1.22 V), this reaction is acucurate. the standard potential is negative, then why all the work for the formation of MnO2 need to be done in anodic potential?
  49. M

    Solving Electrochemistry Lab with Al+3, Cu+2, Fe+3, Zn+2, KNO3

    I'm very confused with an electrochemistry lab. For the lab, we used Al+3, Cu+2, Fe+3, Zn+2, and KNO3. The setup was wells with all of the solutions in them. We soaked a piece of paper(filter paper) in KNO3 for the reactions, then used the paper as a salt bridge between the solutions of the...
  50. J

    How Does Electrode Potential Change in a Mixed Ce4+ and Fe2+ Solution?

    1. Homework Statement Given the following half-reactions: Ce4+ + e− → Ce3+ E° = 1.72 V Fe3+ + e− → Fe2+ E° = 0.771 V A solution is prepared by mixing 7.0 mL of 0.30 M Fe2+ with 8.0 mL of 0.12 M Ce4+. Calculate [Ce4+] in the solution. I've got the potential of a platinum electrode...
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