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. Feodalherren

    Chemistry redox reaction - gases mixing

    Homework Statement How many milliliters of Cl2 gas, measured at 28.0 °C and 750 torr, are needed to react with 18.5 mL of 0.173 M NaI if the I- is oxidized to IO3- and the Cl2 is reduced to Cl-? Homework Equations The Attempt at a Solution So the molar mass is .0030906 mol NaI...
  2. Q

    Redox Reactions: Why Doesn't 1 M NaOH Spontaneously Reduce Hydronium?

    Homework Statement Which of the following does not spontaneously reduce 1 M hydronium ion? Homework Equations Spontaneous reduction: + E-zero value. The Attempt at a Solution The answer is 1 M NaOH. However, sodium is a very strong reducer. Why doesn't this reaction go...
  3. C

    Redox reactions oxidation number method

    1) Problem Statement 2) Relevant Equations3) Attempt at Solution For question d, I realize in this case that the substance that is oxidized and reduced is the same molecule : iodine. How do I proceed then as the next step would ask for you to find the change in oxidation numbers and multiplying...
  4. B

    Why Don't Redox Reactions in Water Occur as Expected?

    The partial pressures of O2 and H2 in the atmosphere above water are typically very low indeed, so why is it we don't see the equilibria 2 H2O = O2 (g) + 4H+ + 4e- and 2 H+ + 2e- = H2 (g) occurring whenever we have a beaker of water (if this was observed then the H+ concentration would be...
  5. S

    Balancing Redox Reactions in Acid and Basic Solutions

    I understand the concept of balancing chemical equations but in the case of redox reactions I don't understand the physical meaning of balancing in acid medium and balancing in Basic medium. Sure, I know how to balance the equation but I want to know what it means physically. Why do we need to...
  6. D

    Algebraic method to balance redox equations

    Hi all, I'm learning how to solve redox equations. I found the algebraic method to solve equations such as this one: Fe^{2+} + Cr_{2}O_{7}^{2-} +H^{+}\rightarrow Fe^{3+} + Cr^{3+} + H_{2}0 and i was able to solve it. What I don't see is how to use that algebraic method to solve an...
  7. WaterMelllon3

    Redox reaction formulas or corrosion formulas?

    I was just wondering if anyone has some redox reaction formulas or corrosion formulas? Cheers Darryl
  8. B

    How Is the Redox Equivalence Point Defined and Calculated in Complex Reactions?

    I had a look at an online page for redox titrations (http://www.titrations.info/potentiometric-titration-equivalence-point-calculation). I can extend my understanding of that page far enough to say that for two half-reactions vA A + ve1 e- ⇔ vB B (vSpecies is the stoichiometric coefficient) and...
  9. B

    Redox Equilibrium Homework Solutions

    Homework Statement I.) Give an estimate for the stability constant of the complex [FeCl]2+, given that the standard redox potential for the Fe3+/Fe2+ system in 1 moldm-3 HCl is 0.710 V. The "standard electrode potential of the reaction Fe3+ + e- -> Fe2+" (quote from the question) had...
  10. D

    Is a Reaction with Slight Electronegativity Difference Still a Redox Reaction?

    does a reaction involving transfer of an electron between atoms with slight difference in electronegativity still count as a redox reaction?
  11. K

    Oxidation Reduction (redox) Balancing

    When balancing oxidation reduction reactions involving acids or bases, what (in the case of acids) allows you to add H+ ions to one side of the reaction and H2O to the other, or in the case of bases, OH- and H2O to balance out hydrogen/oxgen? Normally you are not allowed to just add random...
  12. G

    Need help balancing Redox Reaction

    Homework Statement Can somebody help me balance this redox reaction using either the redox number method or the half equation method? Thank You Na2S + Ag + HNO3 + Na2CrO4 ----> Ag2S + Cr(NO3)3 + NaNO3 Can you please explain your steps. Thank YouHomework Equations The Attempt at a Solution I...
  13. H

    Electrode Potentials and Redox reactions

    What is the relation between Electrode Potentials and Redox reactions ? Can we determine the relative strength of reduction of a metal by looking just at the electrode potentials ? Here is a particular thing that confuses me : We know that the standard electrode potential of Lithium is...
  14. Mandelbroth

    Redox Reaction (An Easier Way?)

    Homework Statement From 9th edition of Raymond Chang's Chemistry (Problem 4.108): "When 2.50 g of zinc strip were placed in a AgNO3 solution, silver metal formed on the surface of the strip. After some time had passed, the strip was removed from the solution, dried, and weighed. If the mass of...
  15. M

    Balancing Redox equations half reaction method

    Homework Statement This is my equation. I needed to balance it in an acidic solution. H2O2(aq)---->H2O(l) Homework Equations I know that you should balance oxygen using H2O & hydrogen using H+. I am confused on how you balance the ionic charges. The Attempt at a Solution...
  16. O

    Redox trends of the first row transition metals

    Hey, I'm having trouble understanding the trends of the oxidation states for the first row of the transition metals -my prof said that Cu is the only metal that forms a stable +1 oxidation state. But, I've done a question in hmwrk that had Cu+1 as unstable with respect to disproportionation how...
  17. D

    Question about Balancing Redox Reactions

    I'm not really sure exactly if I'm doing these correctly but what stopped was the choice of adding 6 electrons to the left side.. This is what I did: This is their answer: I'm doing something wrong and I don't know why my answer is so different then theirs.
  18. B

    Balancing a Redox Reaction in Acidic Solution

    I can balance this equation using the half reaction method, but I want to learn to use the oxidation number method with this particular question to "broaden my abilities". Homework Statement ICl → Cl- + IO3 + I2 The Attempt at a Solution I: +1 → +6: lost 5e- I: +1 → 0: gained 1e- (I'm...
  19. AGNuke

    Simple Redox Balancing, need confirmation

    Question Cr2O72- + H2O2 → Cr3+ + O2 Attempt Cr2O72- + 3H2O2 + 8H+ → 2Cr3+ + 3O2 + 7H2O Is my attempt correct. I think I had lost my grip in redox balancing.
  20. T

    How Do You Balance the Redox Reaction Involving C2H5OH and I3-?

    Homework Statement C2H5OH(aq) + I3-(aq) → I-(aq) + CO2(g) + CHO2-(aq) + CHI3(aq) Homework Equations The Attempt at a Solution I am stuck on how to get C to combine with I in CHI3. Thanks.
  21. R

    Redox Titration Question - Answer Check & Questions

    Good day! I would just like to confirm a couple things in regards to my solution for this problem. Problem: A sample of hydrated ethanedioic acid crystals (formula H2C2O4 . 2H2O) of mass 0.2145g was dissolved in water and the solution was used to standardise some potassium permanganate...
  22. R

    Balancing Redox Equations Using Oxidation Numbers

    Question Balance the following redox using oxidation number. Please show all steps. NaIO3 + NaI + HCl -> NaCl + I2 + H2O Attempted Solution So first I assigned oxidation number: NaIO3 + NaI + HCl -> NaCl + I2 + H2O 1+ 5+ 2- | 1+ 1- | 1+ 1- | 1+ 1- | 0 | 1+ 2-...
  23. L

    Redox reaction; standard cell potential

    Homework Statement Find the cell potential of the equations Mg^+2 + 2e- --------> mg E=-2.36v Cl2 + e- ---------> 2cl- E=+1.36v Ans: -1.00v The Attempt at a Solution The answer says that it cl2 should be flipped. And cl2 is the anode But I don't understand why. I...
  24. agnibho

    Oxidation Number to balance a redox reaction

    Homework Statement Balance Cl2+NaOH -> NaCl + NaClO3 + H2O
  25. T

    Half Reactions of Fe and CuSO4: Understanding Redox Chemistry

    Homework Statement What are the half reactions of Fe + CuSO4→ Cu + FeSO4 Homework Equations The Attempt at a Solution i think it is Fe→Fe2++ 2e- and Cu2++2e-→ Cu I don't know where the SO4 comes in. is it a spectator ion
  26. L

    Is Asea's Redox Product Scientifically Proven?

    Redox and the product "Asea" Has anyone else ever heard of this stuff? I notice from the video that they claim to be "very scientifically backed," according to the homeopathic Dr.. Does anyone have any Scientific Data or insight regarding this product, or or the "Redox" on which it depends?
  27. K

    Redox Reactions and standard emf calculations

    What is the equation I should be using for the following question: At 298K a cell reaction has a standard emf of +0.17V. The equilibrium constant for the cell reaction is 5.5 X 10^5. What is the value of n for the cell reaction. Grateful for anyone's help!
  28. M

    Balancing Redox Reaction by Half Reaction Method

    Homework Statement CuCl2(aq)+Al(s)→AlCl3(aq)+Cu(s) Homework Equations The Attempt at a Solution I'm just not sure what to do with a situation involving compounds. I can do simple balancing without a problem. Here is my attempt. Please, please let me know where I went wrong...
  29. P

    How to choose a reduced or oxidated form in a redox

    Hi guys I'm studying about general chemistry in a physics class. I've some exercices that I'm unable to solve, stuff like this:Copper can be solubilizated in water, oxidating in Cu++ form, reacting with HCrO4- in an acid environment realized by H2SO4. Write down the balanced reaction.my problem...
  30. J

    Redox Titrations Bleach help

    Redox Titrations Bleach! help! Homework Statement An unknown metal hypochlorite salt, M(ClO)2, is subjected to analysis by iodometric titration: the salt is dissolved in dilute sulfuric acid, treated with excess aqueous KI, and then titrated with Na2S2O3 in the same manner as your experiment...
  31. M

    Understanding Redox Reactions: A Beginner's Guide

    I know this is going to be a very simple question to ask so I hope to not bore anyone. I am having trouble with redox reactions. Not so much in completing them but in understanding them. The problem that I have is telling when something is reduced or oxidized. I know if it gains electrons...
  32. J

    Understanding the Role of Ions in Corrosion of Metals in Aqueous Environments

    I have some questions concerning the tendency of a system containing two different metals and water to corrode. This is coming from several similar discussions on another forum, concerning water cooling of computer components. There seems to be a lot of repeated dogma, which may include...
  33. E

    Can you get redox potential from dissolved oxygen in water?

    Hi there, I am trying to get the Eh (or pe) of water samples which I took last summer. I didn't measure it directly at the time. I do have dissolved oxygen values from each site. Is there a way to convert dO2 into Eh? All the dO2 values were in the 80-100% range. Alternatively, is...
  34. E

    I don't understand what causes redox reactions to occur.

    For example, on this website http://www.chemguide.co.uk/physical/redoxeqia/combinations.html in the second diagram from the top, it shows that *if a high resistance voltmeter is placed between two pieces of metal, zinc and copper, the zinc metal will accumulate a build up of electrons.* Then...
  35. T

    Balancing Redox Reactions: CH4 + O2 --> CO2 + H2O

    a. CH4(g) + 2O2(g) ----------> CO2(g) + 2H2O(g) I need to determine which is reduced and which is oxidized, I already know that C in methane is Oxidized. O2 is reduced but how can you determine that?? I know it has to do with electron transfer but I just don't see it
  36. P

    Redox reactions chlorine water

    Homework Statement I am having trouble trying to find out if things react with each other or not. I don't really know how to read the reactivity series well :confused: Homework Equations Question 1: a student was given a beaker of an unknown ionic solution to identify. she conducted the...
  37. V

    Balancing redox equations using 1/2 reaction method

    Homework Statement Balance PbO2(s) + Cl(-) → PbCl2(s) + O2(g) Homework Equations n/a The Attempt at a Solution Pb(4+) + 2e(-) → Pb(2+) and I'm stuck because there's no 2nd reaction.
  38. H

    Understanding Redox Reactions: Balancing Multiple Reductions and Oxidations

    I am supposed to balance the following reaction: CdS + HNO3 (dil) → Cd(NO3)2 + NO + S + H2O After writing out all the oxidation numbers for each atom, I found that Cd and N are both reduced (Cd5+ → Cd 1+ and N5+ → N2+). I am wondering how to approach this problem. Is it possible to have 2...
  39. F

    Redox Battery electrolyte help

    I am wanting to build a small scale Redox flow battery as a fun project. I know there is a list of flow batteries right now and I am trying to decide on one where the elements used are economical as well as one where the watt density is reasonably high. At least twice lead acid anyway...
  40. S

    Why Does Chlorine Gas Form at the Anode in the Chlor-Alkali Process?

    Redox reaction...with a twist! In the chlor-alkali process OH–(aq) and Cl2(g) are produced by the electrolysis of a saturated solution of sodium chloride. Explain why chlorine gas rather than oxygen gas forms at the anode. The solution to the question has the word "Overpotential" and I...
  41. F

    Redox and other unique battery solutions

    We are working on some design ideas to hopefully eventually get our shop and home off the grid with independent power. We are in one of the best locations for wind generation but energy storage becomes an issue and a grid tie system is simply impractical and will not obtain our goals. the...
  42. S

    How Do You Calculate Wine Redox Titration Results?

    Hi guys, A few days ago we conducted a wine redox back titration in my chemistry class, and my teacher has asked us to calculate to answer all of the questions on a sheet she gave us. Attached is this sheet, outlining the method we followed, the materials used and all the questions she wants...
  43. djh101

    REDOX Half Reaction and Net Ionic

    Just need some clarification as to whether or not I'm doing this right. 1 drop HCl and several drops KMnO4 added to 2mL NaHSO3. HSO3- → HSO4- + 2e- MnO42- + 4e- → MnO22- 2HSO3-(aq) + MnO42-(aq) → 2HSO4-(aq) + MnO22-(aq) A few questions: -Since NaHSO3 is not an acid, the hydrogen atom...
  44. A

    Balancing redox reaction by half-reaction method

    Homework Statement Balance the following equation by the half-reaction method. The reaction takes place in basic solution. Fe(OH)2(s) + O2(g) --> Fe(OH)3(s)The Attempt at a Solution All the other problems like this had 2 reactants and 2 products. What's confusing me about this problem is that...
  45. K

    Balancing Redox Reactions (another question) help?

    Homework Statement Use half reactions to balance the following redox reactions and underline the oxidizing agent m) Zn + HNO3 --------> Zn(NO3)2 + NH4NO3 + H2OHomework Equations Not applicableThe Attempt at a Solution I would usually start by breaking down the equation into half reactions, but...
  46. K

    Balancing Redox Reactions using half reactions?

    Homework Statement Use half reactions to balance the following redox reactions and underline the oxidizing agent. a) Cl2 + ClO3{-} -> ClO{-} (acidic) {} is the charge e{-} is electrons Homework Equations Not applicable The Attempt at a Solution Well I tried to separate and...
  47. W

    What Causes Electron Transfer in Redox Reactions?

    Hi, I have a question about redox reactions. What actually causes the transfer of electrons to occur between elements? For example, in the reaction between aqueous Ag+ and solid Cu, why is it more energetically (?) favorable for copper's electrons to transfer to silver, thus creating blue...
  48. A

    What Does a Muddy Precipitate Indicate in a Redox Reaction?

    Homework Statement "State what you would infer from each of the following observations and suggest experiments you would carry out to test the validity of your inferences: When an unpleasant smelling gas was bubbled into an orange solution of a substance 'A', a solid was formed and the mixture...
  49. F

    Chemistry Balancing Redox Reactions

    Homework Statement H_{2} + O_{2} \rightarrow H_{2}O Homework Equations The Attempt at a Solution Well, my classmates insist that H= +1 and O= -2 (in the products side) so, my Hydrogen will be my Reducing agent because it underwent Oxidation and my Oxygen will be my Oxidizing...
  50. S

    Chemical Equation of Redox Reactions

    Homework Statement Please help me in chemical equations of redox reactions. Here are the problems. 1. Mixing potassium dichromate, K2Cr2O7, and sulfuric acid, H2SO4, in a test tube. Then, add hydrogen peroxide, H2O2, drop by drop, shaking the solution after every drop. Add until a change...
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