1 / 24

Redox reactions

Redox reactions. Gain oxygen. Gain oxygen. Loss electrons. Oxidation. 2Mg(s) + O 2 (g)  2MgO(s) CH 4 (g) + O 2 (g)  CO 2 (g) + H 2 O( ) Mg(s)  Mg 2+ (aq) + 2e -. Loss oxygen. Gain electrons. Reduction. 2PbO(s) + C(s)  2Pb(s) + CO 2 (g) Pb 2+ (aq) + 2e -  Pb(s).

hadar
Download Presentation

Redox reactions

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Redox reactions

  2. Gain oxygen Gain oxygen Loss electrons Oxidation • 2Mg(s) + O2(g)  2MgO(s) • CH4(g) + O2(g)  CO2(g) + H2O() • Mg(s)  Mg2+(aq) + 2e-

  3. Loss oxygen Gain electrons Reduction • 2PbO(s) + C(s)  2Pb(s) + CO2(g) • Pb2+(aq) + 2e-  Pb(s)

  4. Oxidation and Reduction

  5. oxidation Oxidizing agent • Oxidizing agent • A substance that causes oxidation is called an oxidizing agent. • An oxidizing agent is a substance that gains electrons. • 2PbO(s) + C(s)  2Pb(s) + CO2(g) oxidizing agent • Pb2+(aq) + 2e-  Pb(s) oxidizing agent

  6. reduction Reducing agent • Reducing agent • A substance that causes reduction is called a reducing agent. • A reducing agent is a substance that loses electrons. • 2PbO(s) + C(s)  2Pb(s) + CO2(g) reducing agent • Pb(s)  Pb2+(aq) + 2e- reducing agent

  7. Oxidizing agent and Reducing agent

  8. Oxidation numbers • The oxidation number of an element is zero. • oxidations numbers of N in N2, O in O2, S, Na, K, Cu are all zero. • The oxidation number of an atom in ionic form is equal to the charge on the ion. • oxidation number of iron in Fe3+ is +3 • oxidation number of oxygen in O2– is –2

  9. Oxidation numbers • The oxidation numbers of all atoms in a neutral compound added together must be zero. • MgO: Mg = +2, O = -2 • KCl: K = +1, Cl = -1 • ZnS: Zn = +2, S = -2

  10. Oxidation numbers • Some elements have fixed oxidation numbers in compounds • all alkali metals (Group I) in compounds must be +1 • Na in NaCl, K in K2SO4 • hydrogen in most of its compounds +1 • H in H2O, H in HCl, H in NH3 • Exception: H in metal hydride e.g. H in NaH is -1

  11. Oxidation numbers • Some elements have fixed oxidation numbers in compounds • all alkaline earth metals (group II) in compounds must be +2 • Ca in CaCO3, Mg in MgCl2 • fluorine in its compounds must be –1 • F in NaF, F in HF

  12. Oxidation numbers • Some elements have fixed oxidation numbers in compounds • oxygen in most of its compounds –2 • O in H2O, O in MgO • Exception: O in peroxide e.g. O in H2O2 is –1

  13. Oxidation numbers • The sum of oxidation numbers of all atoms in an ion is equal to the charge of the ion. • OH-: O = -2, H = +1 • NO3-: O = -2, N = +5 • SO42-: O = -2, S = +6 • NO2-: O = -2, N = +3 • SO32-: O = -2, S = +4

  14. Oxidation numbers

  15. Oxidation numbers

  16. reduction +2 0 0 +2 Mg(s) + CuSO4(aq)  MgSO4(aq) + Cu(s) Oxidizing agent Reducing agent oxidation Redox reactions • Displacement reaction

  17. reduction 0 +2 +1 0 Zn(s) + 2HCl(aq)  ZnCl2(aq) + H2(g) Oxidizing agent Reducing agent oxidation Redox reactions • Metal with acid

  18. The electrochemical series of metals

  19. The electrochemical series of metals • Cu2+(aq) is lower than H+(aq) ion in the e.c.s., it is a stronger oxidizing agent and thus it discharges (reduces) more readily.

  20. The electrochemical series of non-metals • OH-(aq) is higher than halides ions in the e.c.s., it is a stronger reducing agent and thus it discharges (oxidizes) more readily.

  21. Common oxidizing agents

  22. Common oxidizing agents • Acidified potassium permanganate, KMnO4 • Acidified sodium dichromate, Na2Cr2O7 • Concentrated sulphuric acid, H2SO4 • Dilute or Conc. nitric acid, HNO3 • Halogens: Cl2, Br2, etc. • Iron(III) ion, Fe3+(aq) • Metal ions low in e.c.s. e.g. Ag+(aq), Cu2+(aq) • Oxygen gas, O2(g)

  23. Common reducing agents

  24. Common reducing agents • Metal high in e.c.s. e.g. K(s), Na(s) • Hydrogen gas, H2(g) • Carbon, C(s) and carbon monoxide, CO(g) • Sulphur dioxide, SO2(g) and sulphite, SO32-(aq) • Iodide ion, I-(aq) • Iron(II) ion, Fe2+(aq)

More Related