What is Redox: Definition and 214 Discussions

Redox (reduction–oxidation, pronunciation: RED-oks or REE-doks) is a type of chemical reaction in which the oxidation states of atoms are changed. Redox reactions are characterized by the actual or formal transfer of electrons between chemical species, most often with one species (the reducing agent) undergoing oxidation (losing electrons) while another species (the oxidizing agent) undergoes reduction (gains electrons). The chemical species from which the electron is removed is said to have been oxidized, while the chemical species to which the electron is added is said to have been reduced. In other words:

Oxidation is the loss of electrons or an increase in the oxidation state of an atom, an ion, or of certain atoms in a molecule.
Reduction is the gain of electrons or a decrease in the oxidation state of an atom, an ion, or of certain atoms in a molecule (a reduction in oxidation state).Many reactions in organic chemistry are redox reactions due to changes in oxidation states but without distinct electron transfer. For example, during the combustion of wood with molecular oxygen, the oxidation state of carbon atoms in the wood increases and that of oxygen atoms decreases as carbon dioxide and water are formed. The oxygen atoms undergo reduction, formally gaining electrons, while the carbon atoms undergo oxidation, losing electrons. Thus oxygen is the oxidizing agent and carbon is the reducing agent in this reaction.Although oxidation reactions are commonly associated with the formation of oxides from oxygen molecules, oxygen is not necessarily included in such reactions, as other chemical species can serve the same function.Redox reactions can occur relatively slowly, as in the formation of rust, or much more rapidly, as in the case of burning fuel. There are simple redox processes, such as the oxidation of carbon to yield carbon dioxide (CO2) or the reduction of carbon by hydrogen to yield methane (CH4), and more complex processes such as the oxidation of glucose (C6H12O6) in the human body. Analysis of bond energies and ionization energies in water allow calculation of the redox potentials.

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  1. barryj

    Chemistry What is the purpose of redox reactions?

    I am trying to understand redox reactions. I have read, and learned about oxidation numbers and even viewed examples of balancing redox equations. However, nowhere have I seen an explanation of why I care about redox equations. In contrast, I understand that a chemical equation must be balanced...
  2. somasimple

    Redox products with inert electrodes?

    Hello, What are the oxidation-reduction reactions that are produced at the electrodes when they are considered inert (platinum or silver coated)? Let's take a simple example of a saline solution of KCl and apply a DC voltage between the two electrodes. Thank you in advance.
  3. I

    Chemistry Redox Reaction when a compound is both oxidized and reduced

    For the reaction between hydrogen peroxide and sodium hypochlorite, is the OCl- both reduced and oxidized? H2O2 + NaOCl -> NaCl + H2O + O2 Oxidation states: +1 -1 +1 -2 +1 +1 -1 +1 -2 0 From the oxidation...
  4. P

    Chemistry Solving for electron activity given pH and ratio of redox elements

    I've written out the half reaction 8e- + 9H+ + SO42- = HS- + 4H2O and I know the logK = 4.25 (that's the constant mentioned in the prompt) I've written out the equilibrium statement of 10^4.25 = ([x^1/8]*[H2O^1/2])/([10x^1/8]*[e-]*[(10^-8.2)^9/8] However, from there, it seems like I have two...
  5. D

    Chemistry Balancing Redox Reaction: FeS2+Na2O2→Na2FeO4+Na2SO4+Na2O"

    FeS2+Na2O2->Na2FeO4+Na2SO4+Na2O Fe2+ --->Fe+6+4e- 2S-1 --->2S+6+14e- 2O- + 2e- ---> 2O The first two have a total of 18 electrons so In order to balance the electrons i should multiply by 9 the third semireaction (2O- + 2e- ---> 2O-2)x9 now this 9 is going to multiply the left hand in...
  6. 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...
  7. nineteen

    How to get the balanced redox equation in this sample problem?

    Summary: Our chemistry teacher gave a sample problem regarding balancing a redox equation. I managed to proceed to a considerable distance, but I can't seem to understand how to get the final balanced equation. Please help me out. The problem is; reaction of K2Cr2O7 with SO2 in the presence of...
  8. K

    Investigating the Stoichiometry of Reactions 1 & 2

    Cl2(g) + 2I–(aq) -->I2(aq) + 2Cl–(aq) (reaction 1) [2S2O3^(2-)(aq) + I2(aq) --> S4O6(2-)(aq) + 2I–(aq) (reaction 2) Why isn't n(I2)(reaction 2)=2n(S2O3^(2-))(reaction 2). I don't see why this is wrong. <edit: remove size and italics>
  9. somasimple

    RedOx Reactions & Phase Changes

    Hi, In electro-chemical cells (galvanic, concentration, etc) or more generally when some RedOx reactions occur in solutes, is there always a phase change? I mean is there always a change in the state of matter from liquid to solid or gas?
  10. J

    Copper (II) salts and SO2: a question

    The reaction below moves left to right (I expect it has an equilibrium somewhere): SO2(g) + 2 CuCl2(aq) + 2 H2O → H2SO4(l) + 2 HCl(l) + 2 CuCl(aq) I'm wondering if copper (II) acetate will work in place of copper (II) chloride: producing acetic and sulfuric acids instead of hydrochloric and...
  11. S

    Optimizing Redox Reaction of FeO with H2

    Greetings, ME major here trying to brush the cobwebs off my chemistry. I can't seem to remember or recognize anything on my old chemistry textbooks regarding the optimization of a reaction. I question whether it was even taught. I'm trying to determine the most favorable conditions to ensure...
  12. C

    Why is activity of solvated components equal to 1?

    Homework Statement Consider the following reaction $$\mathrm{Ni^{2+}_{(aq)} + H_2S_{(g)} \to Ni_{(s)} + S_{(s)} + 2H^{+}_{(aq)}}$$ What are the activities of the terms in the reaction? Homework Equations The activity is defined as ##a = c/c^\circ## in ##\mathrm{ mol \, dm^3}## 3. The...
  13. alphaj

    Redox Reaction in Dissolved Ammonium Chloride

    Quick note: Sorry for dominating the homework help board, guys! But, I wanted to say thank you to everyone who replies to my excessive questions. This forum's input has become integral to me as I am in a position now where I can't go to my teacher for help because of the logistics of commuting...
  14. 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
  15. Wrichik Basu

    A problem in Redox Titrations (Kjeldhal's Method)

    Homework Statement :[/B] 1.08g of ##NH_4 Cl## is boiled with 62ml ##\frac {N}{2}## ##NaOH## to expel ##NH_3## completely. 44ml of ##\frac {N}{4}## ##HCl## is required to neutralise the excess alkali. Calculate the percentage of ##NH_3 ## in ##NH_4 Cl##. Answer given: 31.5% Homework Equations...
  16. erbilsilik

    CV redox peaks and Gamry Potentiometer

    I'm using Gamry Potentiometer for taking CV measurements for finding the appropriate voltage values for oxidation/reduction peaks and Echem Analyst for analyzing. CV measurements has performed on liquid electrolyte in order to find if working electrode accept Li ions. My question is about...
  17. T

    Electron transfer and oxidation state

    When beryllium donates a pair of electrons to oxygen, that's oxidation, and the metal is Be(II). When carbon and oxygen share 6 electrons, 2 from carbon and 4 from oxygen, this is also oxidation. Of carbon. Even though it got more electrons, and even, I heard, has a negative charge. When...
  18. N

    MHB Chemistry: Balancing Redox reactions

    What do i have wrong here for my chemical equation? Seems to be right but my homework won't accept it. Balance the redox reaction occurring in acidic solution. Sn(s)+MnO−4(aq) → Sn2+(aq)+Mn2+(aq) Express your answer as a chemical equation including phases. 5Sn+2MnO−4+16H+→5Sn2++2Mn2++8H2O...
  19. B

    Why there are infinite ways to balance this Redox equation?

    Homework Statement Balance :- $${Cl_2O_7} + {H_2O_2} {\longrightarrow} {ClO_2^-} +{O_2} + {H^+}$$ Medium :- basicHomework EquationsThe Attempt at a Solution $${\stackrel{+7}{Cl_2}\stackrel{-2}{O_7}} + {\stackrel{-1}{H_2}\stackrel{-1}{O_2}} {\longrightarrow}...
  20. S

    Redox reactions and potentials/potential differences

    Hello to everyone who reads this. :) Homework Statement I DO understand the two following points.: 1. If the redox potential of a redox reaction is positive, then the redox reaction is spontaneous. 2. If the redox potential of a redox reaction is negative, then the redox reaction is NOT...
  21. A

    Questions about Redox Reactions

    Hello, Firstly, I apolagize if this should go in "HW help". It isn't homework, and the question doesn't fit the format of "HW help", but it is so elementary, so I don't know. I'll write my questions in bold. Although I think I understand what redox reactions are--a reaction in which an...
  22. ashsully

    Fixing a Rusted Snowboard Edge with REDOX Reactions

    Homework Statement Hi all, I'm fairly new to physics forums so cut me some slack for being a noob. I've just noticed that my brand new snowboard's edge has rusted (oxidised). I live in Australia and it's been stored in my room receiving sunlight everyday. I'm guessing this probably caused the...
  23. D

    Can Methane and Citric Acid be Balanced in a Redox Reaction?

    Hi there: I'm trying to balance a reaction in which methane is oxidized by citric acid in solution. Both methane and citric acid will be transformed into carbon dioxide. To begin, I checked that the reaction is indeed a redox reaction. C6H8O7→CO2 So, I calculated the oxidation number for...
  24. Clara Chung

    Please help with a redox multiple choice

    1. The equation below represents the reaction of chlorine with hot concentrated potassium hydroxide solution: 3Cl2(g) + 6KOH(aq) → 5KCl(aq) + KClO3(aq) + 3H2O(l) Which of the following statements concerning this reaction is/are correct? (1) Potassium hydroxide acts as a reducing agent (2)...
  25. Revengeance

    Why can't all metal oxides be reduced by a redox

    how come they all cannot be reduced by a reducing agent such as hydrogen or carbon, why is it that only some can, the only thing i came up with is that, only those metals that are listed under the activity series can.
  26. Stephanus

    Exploring the Role of Antioxidants and Reducing Agents in Redox Reactions

    Dear PF Forum, Lately, I'm trying to understand the benefits of antioxidant. What is the difference between antioxidant and reducing agents? 1. Reducing agent react with (reduce) oxidizing agent to CREATE NEW molecule(s)? 2. Antioxidant reduces the oxidizing agent so it has an additional(s)...
  27. E

    Balancing disproportionation redox reaction

    Homework Statement Complete and balance the following reaction: Cl2 + OH- → Cl- + ClO- Homework EquationsThe Attempt at a Solution So, I did it like any other redox: Cl2 + 2e- → 2Cl- 2Cl2 + 4OH- → 2ClO- + 2H2O + 2e- Net reaction: 3Cl2 + 4OH- → 2Cl- + 2ClO- + 2H2O However, the answer is Cl2...
  28. R

    Balance Redox Reaction: 2PbO2 + 4H+ = 2Pb 2+ + O2 + 2H2O

    Homework Statement Balance the following oxidation-reduction reactions: PbO2 = Pb 2+ + O2 Homework Equations [/B] These are the steps I'm supposed to follow. 1. Determine the valence number (charge) for all the elements involved in the reaction. 2. Determine the number of e- given off...
  29. terryds

    Number of electrons to balance redox reaction

    Homework Statement What number of electrons to balance the equation ##I_2(s)+OH^-(aq)\rightarrow IO_3^-(aq)+H_2O(l)## The Attempt at a Solution I see that the oxidation state of I increases from 0 to +5 But, I don't see any reduction at the reaction.. So, I don't understand how to balance the...
  30. P

    Explain why Zn is released and write the general equation.

    Homework Statement We throw clean Zn in a HCl solution and see that nothing happens. We add 2-3 drops CuSO4 and some kind of gas starts to release. Why dos this happen? Write the equation Homework Equations Zn+HCl->ZnCl2+H2 The Attempt at a Solution I know that equation and also...
  31. P

    Could you help me with this electrolysis equation?

    Homework Statement Write the water electrolise of NaOH. Homework Equations NaOH+H2O->H2+O2+NaOH The Attempt at a Solution 2NaOH+2H2o->2H2+O2+2NaOH I thought to write 2H2O->2H2+O2 If I am given the mass of NaOH (which in one problem I am), then how am I supposed to find the mas of H2O for...
  32. P

    Find the mass of Ag around the Nickel pole

    Homework Statement A nickel pole is put in an AgNO3 solution with volume 50ml and concentration 0.1 mol/litre until the concrentration is 0.02 mole/litre. Find the mass of Ag that is put around the Nickel pole. Homework Equations 2AgNo3+Ni->Ni(NO3)2+2Ag number of moles= concrentration*volume...
  33. P

    Find in which case the Zn pole mass is greater

    Homework Statement A pole of Zn is put in a FeCl2 solution and in a HgCl2 solution. FInd in which case the mass of the pole of zinc has become grater and when less Homework Equations Zn+FeCl2->ZnCl2+Fe Zn+HgCl2->ZnCl2Hg The Attempt at a Solution As Zn is much active than Hg than it goes in...
  34. terryds

    Determine if reactions are redox

    Homework Statement Determine which is/are redox reaction/s ? ##1. 2HNO_2 + 2HBr \rightarrow 2NO + BR_2 + 2H_2O## ##2. PbO_2 + SO_2 \rightarrow PbO + SO_3## ##3. 2Ag + Cl_2 \rightarrow 2AgCl## ##4. SO_2 + NaOH \rightarrow NaHSO_3## Homework Equations Redox reactions are the ones which involves...
  35. S

    A redox titration with kmno4- and h2o2 help

    Homework Statement Calculate the average volume of permangate ion used. I'm given the average volume of kmno4 used. Homework Equations N=m/mm The Attempt at a Solution I tried to just average my kmno4 used, but I don't believe that's what my teacher is looking for. Help?[/B]
  36. R

    Balancing a Redox Equation with Half-Reactions

    It's not clear to me how I can balance the following equation, most of all because of K which I don't know how to deal with: \mathrm{SO_2 + K_2Cr_2O_7 \to Cr_2(SO_4)_3 + SO_3} [this is the text of the exercise] It's acidic solution for sulfuric acid, so the equation can be better written so...
  37. Dong Aleta

    [Compound + Compound = Compound] Reactions: A question

    Hi! I noticed that almost all of the [Compound + Compound = Compound] reactions that I have encountered do not involve any transfer of electrons, or are not oxidation-reduction (redox) reactions. Can it be generalized that all [Compound + Compound = Compound] reactions are not redox reactions...
  38. T

    Basic concept doubts in redox reactions

    Homework Statement [C2O4]-2 ------> CO2 Find if the reaction is oxidation or reduction and determine the no. of electrons lost or gained by carbon. Homework EquationsThe Attempt at a Solution I started with finding the oxidation states of both elements. It's 3+ and 2- for carbon and...
  39. Elvis 123456789

    Is 3FeCl2 to 2FeCl3 and Fe(s) a Disproportionation Redox Reaction?

    Homework Statement Determine the oxidizing agent, reducing agent, element oxidized, element reduced, # of electrons lost per atom, and # of electrons gained per atom. State if the reaction is not redox. 3FeCl2(aq) ------> 2FeCl3(aq) + Fe(s) Homework EquationsThe Attempt at a Solution...
  40. ugenetic

    Relations between workfunction, ionization, redox and fermi

    My understanding so far, critique appreciated: [1] workfunction closely relates to reduction potential Since workfunction is about boundaries and chemical reaction are mostly happening at the boundaries between bulk material, Workfunction should have a direct correlation with reduction...
  41. G

    Why reduced atoms are more energetic?

    For example, in glycolysis, NAD+ is reduced to NADH and then it's more energetic. Why adding electrons to an atom gives it more energy?
  42. C

    Surface area contact with catalyst effect on hydrogen redox

    I have also posted this question here: Relationship between surface area of electrode and reaction rate of hydrogen in fuel cells, but I really need an answer before tomorrow morning so I hope you don't mind me posting it here as well! I am looking at the effects of increasing the surface area...
  43. L

    How do electrolytes conduct electricity without redox?

    Say you have salt water. If you apply an voltage between two electrodes Na+ ions will drift towards the negative electrode and Cl- ions towards the positive electrode. If a redox reaction happens at the electrodes, the ions transfer electrons to the electrodes and current continues to flow until...
  44. W

    Redox reaction-naming the substance reduced

    1) Problem statement: Name the substance reduced in the reaction: PbS + 4 H2O2 --> PbSO4 + 4H2O Explain why the reaction is a redox reaction. 2) Relevent equations: Not much equations... -Reduction is the decrease in the oxidation state of an element in a substance during a reaction. - 3)...
  45. M

    About COMSOL use to model Vanadium Redox Flow Battery (VRFB)

    Dear Friends, Merry Christmas to All. I am pleased to join this forum of Physics Experts. Please I need some help to work on COMSOL, I am about to start learning COMSOL. I'm going to work on this topic ' Vanadium Redox Flow Battery ' (VRFB) and this topic has many physics so it can be...
  46. D

    Calculating Oxidation State of Nitrogen in 2NO + O2 -> 2NO2

    2NO + O2 -> 2NO2 "Oxidation of NO" So a reactant - 2NO doesn't seem to lose an electron, it only gains an additional oxygen atom. So, I guess, oxidation is also gain of an oxygen? ...
  47. N

    Examples and Calculations for Redox Titration

    Actually, what is redox titration? what are the steps of carrying out this typpe of titration? Is it just like the simple titration?? Can anyone kindly list out a few examples, i mean calculations about redox titration? I am thankful if anyone can help.
  48. K

    Redox titration and mass percent composition calculations.

    Homework Statement Hello everyone, I have completed a lab and I’m working on my report. I’m not sure if my work is correct but I would most definitely appreciate it if anyone could check it for me? I’m particularly having trouble finishing question #3. It’s worth a lot of my grade so I want...
  49. K

    Redox titration end point calculation -- Help please

    Homework Statement A student weighs by difference 0.1956 g of sodium oxalate into a 100 ml Volumetric flask and dilutes to the mark 10 ml of HCl and 90 ml of distilled water. Approximately how many ml's of 0.02 M KMnO4 would be required to reach the equivalence point of the titration...
  50. S

    What is the importance of the solution in an electrochemical cell?

    I'm wondering about the importance of the electrolytic solution in an electrochemical cell. For example, we have Zn/ZnSO4 and Cu/CuSO4. According to the electrochemical series, Zn will reduce Cu, and we will have a reaction. Zn(s) -> Zn2+(aq), Cu2+(aq) -> Cu(s). So there MUST be Cu2+ in the...