TRAVISTRA

 NMR SPECTROSCOPY  NMR depends on the absorption of energy when the nucleus of an atom is excited from its lowest energy nuclear spin state to the next higher one.  The nuclear energy levels are produced by keeping nuclei in a magnetic field. The NMR spectrum is produced by EM radiation in the radio wave frequency region (60-500MHz).  NMR spectroscopy deals with nuclei having I=1/2. The spin quantum number (I) is related to the atomic number and mass number of the nucleus. Elements with either odd mass numbers or add atomic numbers have the property of nuclear spin. Radio waves are the lowest energy form of EM radiation. This energy is too small to vibrate, rotate or excite an atom or molecule. It is sufficient to influence the nuclear spin of the atoms of a molecule.  Principle of NMR The nucleus of an atom is positively charged, when it spins it develops a magnetic field and acts like a tiny bar magnet with a magnetic moment (µ) µ= I(I+1)1/2 h/2 π  The sp...

 CONVERGING THINKING AND DIVERGING THINKING  Convergent thinking focuses on finding one well-defined solution to a problem. Divergent thinking is the opposite of convergent thinking and involves more creativity CONVERGING THINKING This type of thinking is best suited for tasks that involve logic as opposed to creativity, such as answering multiple-choice tests or solving a problem where you know there are no other possible solutions.  DIVERGING THINKING Divergent thinking is the opposite of convergent thinking and involves more creativity. With this type of thinking, you can generate ideas and develop multiple solutions to a problem. While divergent thinking often involves brainstorming for many possible answers to a question, the goal is the same as convergent thinking—to arrive at the best solution.  BENEFITS IN CONVERGING THINKING A quicker way to arrive at a solution Leaves no room for ambiguity Encourages organization and linear processes BENEFITS IN DIVERGING T...

 CATHODIC PROTECTION  It is a method of preventing a metallic object from corrosion. It is an electrochemical process in which the metal which is to be protected is forced to act as a cathode. Corrosion occurs only in the anodic area. Therefore the entire surface of the metal can be turned into a cathode, then corrosion can be prevented. In this case, corrosion is not actually eliminated but moved to a known location by adding an anode, which undergoes slow and controlled corrosion. There are two main methods of applying  cathodic protection: Sacrificial anode protection and Impressed current cathodic protection SACRIFICIAL ANODE PROTECTION In this method, the metallic structure which is to be protected is connected to a more anodic metal through a wire, so the entire corrosion is concentrated on the anodic metal, and the metallic structure is protected sacrificially. Anode metals commonly used for this are Mg, Zn, Al, and its alloys.   They are based on the position...

 CORROSION Corrosion is the destruction of metals and alloys by the chemical or electrochemical reaction with the environment.  During corrosion, metals are converted to metallic compounds at the surface and these compounds wear away as corrosion products. The corrosion of iron is known as rusting. Examples of corrosion are: Rusting of iron in the moist atmosphere form Fe2O3.2H2O Formation of basic CuCO3 (green film) on the surface of copper. The reaction of chlorine gas with Mg or Sn. Rate of corrosion It is expressed in Milligrams per year (mpy). mpy= 534W/DAT  Where W=weight loss in mg, D= the density of the material in g/cm2, A= the area of the material in sq. inch, T= exposure time in an hour. Mechanism of Corrosion They are of two types Direct chemical corrosion or dry corrosion (oxidation, corrosion due to other gases, liquid metal corrosion) and Electrochemical corrosion or wet corrosion.0 Electrochemical or WET corrosion This type of corrosion takes place when...

 LITHIUM-ION BATTERY Lithium-ion batteries are secondary rechargeable batteries.  It has an emf that varies from 3.5-4V depending on electrode potential. Construction The 3 primary components of a lithium-ion battery are: The anode is lithiated graphite (graphite in which lithium ions are inserted in between the layer of carbon atoms. The cathode is a mixed metal oxide like LiCoO2,  LiMnO2 or LiFeO2  The electrolyte is a lithium salt (LiPF6, LiBF4, or LiClO4 ) in an organic solvent. This is rechargeable. This is done by applying a higher voltage than the voltage of the battery, across the electrodes. The lithium-ion moves from anode to cathode during discharging and from cathode to anode while charging. Cell reaction Anode : LixC6  --->   6C + x Li+  + x e- Cathode : Li1-x CoO2 + x Li+  + xe ----->   LiCoO2 Overall cell reaction : LixC6 + Li1-x CoO2  ------->   LiCoO2  +6C Characteristics Depending on ...

 FUEL CELL They are electrochemical cells. It is an energy conversion device or electricity generator. ADVANTAGES Fuel cells are efficient and convert about 75%-83% of available chemical energy to electrical energy. The electrode materials are supplied in the gaseous form. Examples H2 , CO, hydrocarbons, coal gas, producer gas etc. It is light, compact, simple and easy to maintain    Whatever may be the electrode material, CO2 and H2O should be the end products. The concentration of the electrolyte remains invariant. Less green house and noise pollution. They can be stacked and connected in series to generate higher voltage without making any noise. Reduces the thermal pollution from power generation. HYDROGEN-OXYGEN FUEL CELL It is based on the reaction, combustion of H2 in O2 to form water. 2H2 +O2   ------->          2H2O       The cell consist of two electrodes made of porous graphite, impregnated with plat...

 GLASS ELECTRODE It is a secondary reference electrode that produces a constant and reproducible electrode potential. It is an ion-selective electrode used with other reference electrodes to generate a potential difference. Construction It is made up of a special glass of relatively low melting point and high electrical conductivity, in the form of a sealed glass tube filled with 0.1M HCl, a platinum wire is inserted into it, to make electrical contact. The glass electrode is represented as Pt| 0.1M HCl | Glass | H+    The H+ ion concentration inside the electrode is constant. When the electrode is immersed into a solution of unknown H+, it becomes sensitive to the outside concentration in the solution. Such a sensitivity arises because of the difference between the H+ ion concentration inside and outside.       The electrode potential of the glass rod is : EG = EG0 + 0.0591 log [ H+ ]     EG = EG0 - 0.0591 pH  The glass electrode i...

CALOMEL ELECTRODE  It is a secondary reference electrode. It consists of a glass tube at the bottom of which is kept, Hg2Cl2, and a solution of KCl. A Pt wire is dipped into the Hg layer used for making electrical contact.  The side tube is used for making electrical contact with the salt bridge. The electrode is represented as Hg| Hg2Cl2| KCl. Electrode reaction is represented as :    2Hg + 2 Cl    ---->       Hg2Cl2 + 2 e- The potential of the electrode depends upon the concentration of KCl solution.  Electrode potential if saturated calomel electrode (SCE) is 0.2422V. Determination of electrode potential (E⁰) using calomel electrode  The electrode whose potential is to be found out is connected with a saturated calomel electrode through a salt bridge internally and the emf of the cell is determined using a potentiometer. 

STANDARD HYDROGEN ELECTRODE  The standard hydrogen is an example of a glass electrode, used as a primary reference electrode whose electrode potential is fixed as zero.  CONSTRUCTION OF SHE Hydrogen gas at 1atm pressure is bubbled through a one molar H+ ions as HCl solution at a temperature of 298⁰K. Under these conditions both hydrogen as well as hydrogen ions will be in their standard state and hence the name standard hydrogen electrode.  The platinum wire makes electrical contact and it is surrounded by an outer glass tube that has an inlet for hydrogen gas at the top and a number of holes at the base for the escape of hydrogen gas. It can act as a cathode as well as an anode depending on the potential of the electrode to which it is coupled.  If the potential of the coupled electrode is less than zero (Zn, Mg, Li) reduction takes place in SHE and it acts as the cathode. If the potential of the coupled electrode is greater than zero (Cu, Ag) oxidation takes place ...