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Electro chemistry



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Electro chemistry

  1. 1. In the name of Allah , the most Gracious , the most merciful . 1
  2. 2. I’m Muhammad Najiur Rahman(Ruman) Welcome To My Presentation 2
  3. 3. Electro-chemistry 3
  4. 4. Overview 4 1.Conductance of Electrolyte 2.Concept of E.M.F 3.Electrode Potential 4.Relation between Electrical &Chemical Energies 5.Interfacial Phenomena & Complexation
  5. 5. Conductance of Electrolyte 5 We have seen that electrolyte solutions conduct electric currents through them by movement of the ions to the elecrtodes. The power of electolytes to conduct electric currents is termed conductivity or conductance. Like metalic conductors, electrolytes obey Ohm’s Law. According to this law, the current l flowing through a metalic conductors is given by the relation, l=E/R where E is the potential difference at two ends (in volts); and R is the resistance measured ohms Ω, we can write as, R α 1/A or, R = ρ × 1/A where ρ ‘rho’ is a constant of proportionality and is called specific conductance. It is defined as: the conductance of cc of solution of an electrolyte. The units of specific conductance is 1/ Ω × 1/cm
  6. 6. Concept of E.M.F 6 The flow of electron through the circuit is determined by the ‘push’ of electrons at the anode & ‘attraction’ of electrons at the cathode. These two forces constitute the ‘electrical pressure’ that sends electrons through the circuit. It is known as electromotive forces or cell potential. The emf of cell potential is measured in units of volts (V) and is also referred to as cell voltage. The emf of a cell can be calculated from the half-cell potentials of the two cells(anode & cathode) by using the following formula , Eo cell = Eo cathode - Eo anode = Eo R - Eo L Eo cell = Eo Rduction - Eo oxidation
  7. 7. Electrode Potential 7 When a metal (electrode) is immersed in a solution containing the ions of that metal, a potential difference is set up between the metal and its ions in the solution. This potential difference is referred to as "ELECTRODE POTENTIAL". If a copper plate is dipped in a solution of copper sulphate (CuSO4) a potential difference is set up between copper and Cu+ -ions which is known as electrode potential. Electrode potential may be positive or negative depending upon the nature of electrode.
  8. 8. Relation Between Electrical & Chemical Energies 8 There are three basic components: positive electrode (cathode, or "positive terminal"), negative electrode (anode or "negative terminal"), and electrolyte. When the positive and negative terminals are connected so that electrons (electricity) can flow between them (usually by a wire), chemical reactions occur at the electrodes. These reactions release excess electrons at the anode which flow to the cathode. The chemical reactions occur between the electrolyte and the cathode and between the electrolyte and the anode. Different types of batteries use different materials for the these three components.
  9. 9. Figure : Batteries transform chemical energy into electrical energy. We can get electrical energies from chemical reactions. So, it is the relation between two of these.
  10. 10. Interfacial Phenomena & Complexation When phases exist together , the boundary between two of them is termed an interface. The properties of the molecules forming the interface are often sufficiently from those in the bulk of each phase that they are referred to as forming an interfacial phase. Very often it is desirable or necessary in the development of pharmaceutical dosage forms to produce multi-phasic dispersions by mixing together two or more ingredients that are not mutually miscible and capable of forming homogeneous solutions. Examples of such dispersions include :  Suspensions – solid in liquid  Emulsions – liquid in liquid  Foams – vapor in liquids 10
  11. 11. What does Complexation mean? Complexation is the combination of individual atom groups, ions or molecules to create one large ion or molecule. One atom or ion is the focal point of the complex. This central atom contains empty electron orbitals that enable bonding with other atoms as well as unshared electrons. The last stage in complexation involves the sum of individual components' charges. Therefore, there can be zero, negative and positive charges in a complex within a solution. To ensure that proper complexation takes place, certain factors should be observed:  Ionic strength  Temperature  pH  Competing ions When these factors are properly controlled, obtaining more accurate complexation values is the major result
  12. 12. Colloid & Macro-molecular System 12
  13. 13. A very large molecule, such as a polymer or protein, consisting of many smaller structural units linked together. Also called super-molecule. A molecule of high relative molecular mass, the structure of which essentially comprises the multiple repetition of units derived, actually or conceptually, from molecules of low relative molecular mass. And the macro/super/large molecule maintain a system , this system is known as macromolecular system
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Editor's Notes

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