Redox titration

Redox titration in analytical chemistry

1. Analytical chemistry

2. Redox titration

3. Content Definition Oxidation and reduction Oxidizing and reducing agent Oxidation state Examples in electrochemical cell Experiment Application References

4. Definition Redox Titration is a laboratory method of determining the concentration of a given analyte by causing a redox reaction between the titrant and the analyte. Titration is a common laboratory method of quantitative chemical analysis to determine the concentration of an identified analyte. A reagent, termed the titrant or titrator, is prepared as a standard solution of known concentration and volume .

5. Titrant: S olution of a known concentration, which is added to another solution whose concentration has to be determined. Titrand or analyte: T he solution whose concentration has to be determined.

6. Explanation Redox Titration explained by following terms https:// www.google.com/url?sa=i&url=https%3A%2F%2Fwww.shutterstock.com%2Fsearch%2Foxidation%2Breduction

7. LEO the lion goes GEO Losing electron is oxidation (LEO). Gaining electron is reduction (GEO).

8. https:// www.google.com/url?sa=i&url=https%3A%2F%2Fstudylib.net%2Fdoc%2F17624001%2Foxidation-reduction

9. Oxidation Oxidation is the  loss of electron An   increase  in the oxidation state of an atom, an ion, or of certain atoms in a molecule. Loss of hydrogen Gain of oxygen

10. Reduction  Gain of electrons A decrease in the oxidation state of an atom, an ion, or of certain atoms in a molecule A reduction in oxidation state.

11. Example

12. Oxidizing agent Oxidizing agent is a substance that oxidizes something else . Oxidizing agents give oxygen to another substance. Example: Cupreous

13. Reducing agent A reducing agent reduces something else. A reducing agent is an element or compound that loses an electron. Reducing agents remove oxygen from another substance . Example: In the equation, the carbon monoxide is the reducing agent .

14. Oxidation state Oxidation state indicates the degree of oxidation for an atom in a chemical compound. Oxidation states  are typically represented by integers, which can be positive, negative, or zero . The oxidation state (OS) of an element corresponds to the number of electrons, e-, that an atom loses, gains, or appears to use when joining with other atoms in compounds.

15. Oxidation State Definition: Valency and oxidation state has direct relation. Combining capacity of an element with other elements is called valency. Or, the bonds of an atom with another bonds. Example: HCl (H-Cl ) The apparent charge on atoms of an element of a molecule is called oxidation state. Examples: H20 (H-O-H)

16. Rules for assigning oxidation states In determining the oxidation state of an atom, there are seven guidelines to follow : The oxidation state of an individual atom is 0.e.g; Na, OS is 0. The total oxidation state of all atoms in: a neutral species is 0 and in an ion is equal to the ion charge .e.g; Na+ ,OS is +1. Group 1 metals have an oxidation state of +1 and Group 2 an oxidation state of +2 The oxidation state of fluorine is -1 in compounds Hydrogen generally has an oxidation state of +1 in compounds Oxygen generally has an oxidation state of -2 in compounds In binary metal compounds, Group 17 elements have an oxidation state of -1, Group 16 elements of -2, and Group 15 elements of -3. The sum of the oxidation states is equal to zero for neutral compounds and equal to the charge for polyatomic ion species .

17. Rules for assigning oxidation Numbers

18. Galvanic cell A galvanic cell or voltaic cell , is an electrochemical cell that derives electrical energy from spontaneous redox reactions taking place within the cell . Example : Daniel cell

19. Reactions in galvanic cell Oxidation Zn(s) Zn 2 + + 2e- Reduction Cu + 2e- Cu(s) Overall cell reaction is Zn(s) + Cu2+(aq) Zn2+(aq) + Cu(s)

20. Electrolytic cell An electrolytic cell is a kind of electrochemical cell. It is often used to decompose chemical compounds, in a process called electrolysis Electrolysis is the Greek word, lysis means to break up . Examples of electrolysis are the decomposition of water into hydrogen and oxygen.

21. Titration of Potassium Permanganate against Oxalic Acid Prepare a standard Oxalic acid solution of about 250 ml. The molecular mass of oxalic acid is calculated by adding the atomic mass of each constituent atom The molecular mass of H2C2O4.2H2O = 126 Since the weight of oxalic acid that is required to make 1000 ml of 1M solution is 126 g . Hence , the weight of oxalic acid needed to prepare 250 ml of 0.1 M solution = 126/1000 x 250 x 0.1 = 3.15 g

22. Determining Strength of KMNO4 using Standard Oxalic Acid Solution In this titration, the analyte is oxalic acid and the titrant is potassium permanganate. The oxalic acid acts as a reducing agent, and the KMnO4 acts as an oxidizing agent. Since the reaction takes place in an acidic medium, the oxidizing power of the permanganate ion is increased. This acidic medium is created by the addition of dilute sulfuric acid.

23. KMnO4 acts as an indicator of where the permanganate ions are a deep purple color. In this redox titration, MnO4– is reduced to colorless manganous ions (Mn2+) in the acidic medium. The last drop of permanganate gives a light pink colour on reaching the endpoint. The following chemical equation can represent the reaction that occurs.

24. End point of redox titration Selecting and evaluating the end point. A redox titration’s equivalence point occurs when we react stoichiometrically equivalent amounts of titrand and titrant. As is the case for acid–base titrations and complexation titrations, we estimate the equivalence point of a redox titration using an experimental end point. A variety of methods are available for locating a redox titration’s end point, including indicators and sensors that respond to a change in the solution conditions.

25. Indicators A redox indicator is an indicator which undergoes a definite color change at a specific electrode potential. Example : diphenylamine Three types of indicators are used in redox Titration. Self indicator Internal indicator External indicator

26. Self indicator: It is actually a chemical substance which can mark the end point of a titration or any other reaction along with self-participation in the reaction. Example: I2 and KMNO4. Internal indicator: Indicators in which one of the reactants behaves as an indicator is known as an internal indicator.  Example: Diphenylamine External Indicator:  External indicators are those which are added from outside that is they do not exist in the reaction. Example: Phenolphthalein, Methyl orange

27. Application Redox titration determines the concentration of an unknown solution( analyte) that contains an oxidizing or reducing agent . It provide pharmacopeial methods for the assay unformulated drugs and excipients and some formulated drugs. Examples: those lack strong chromophore. Used for standardization of raw materials and intermediates used in drug synthesis. Certain specialist titration such as Karl Fischer.

28. Applications Agriculture: NO3,Nh3,I, K ,CN , Cl in solids , plant materials , feed stuffs , fertilizers. Detergent manufacturing: Ca , Ba , F for studying effects in water quality.

29. Applications : One of the titration methods used in hydrometallurgy is an oxidation-reduction (redox) titration. Redox titrimetry is used to analyse a wide range of inorganic analytes. Redox titrimetry is based on a redox reaction between the analyte and titrant.

30. Questions related to the topic Oxidation/ reduction Reducing agent / oxidizing agent Examples of oxidation state Redox titration in electrochemical cell

31. References https://byjus.com/chemistry/redox-titration/ https :// chem.libretexts.org/Bookshelves/Analytical_Chemistry/Supplemental https://chem.libretexts.org/Bookshelves/Analytical_Chemistry/Supplemental_Modules_(Analytical_Chemistry)/ Electrochemistry/Redox_Chemistry/Oxidation-Reduction_Reactions https:// en.wikipedia.org/wiki/Electrolytic_cell https:// en.wikipedia.org/wiki/Galvanic_cell https:// en.wikipedia.org/wiki/Redox_titration https://courses.lumenlearning.com/introchem/chapter/oxidation-states/#:~:text=Oxidation%20state%20indicates%20the%20degree,positive%2C%20negative%2C%20or%20zero . https://byjus.com/chemistry/titration-of-oxalic-acid-with-kmno4 / https://byjus.com/chemistry/redox-titration / https:// youtu.be/FSJUZvCrZiU https:// youtu.be/nVoSvpf4hXY https:// youtu.be/nVoSvpf4hXY