TRAVISTRA

 IR VIBRATIONAL SPECTROSCOPY  It involves the transition between vibrational energy levels of a molecule. It arises due to the change in dipole moment with the vibration of a bond.  The vibrational spectra are given by the EM radiations in the IR region of range 500-4000cm-1  This type of spectrum is given by diatomic molecules with permanent dipole moments like HCl, H2O, and molecules with fluctuating dipole moments like CO2. These are IR-active molecules. Compounds which are IR inactive are H2 , O2, N2, Cl2  It is also called vibrational rotational spectrum since the rotational energies are smaller than vibrational energies so both vibration and rotation occur simultaneously.  It is used to establish the identity of a compound or determine the structure of a new compound. It can also predict the functional groups which absorb at definite frequencies. PRINCIPLE The movement of atoms and the chemical bonds (vibration) is like a spring and ball. The characteristic vibration is called t

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 ELECTRONIC TRANSITION  1. σ-------> σ* transitions       An electron is excited from the bonding σ orbital to the corresponding σ* orbital. The transition energy required is very high. This type of transition occurs below 150nm. Therefore the absorption occurs in the vacuum UV region. This type of transition occurs in saturated hydrocarbons. Thus saturated hydrocarbons do not show any absorption in the UV, visible region. Therefore they are colorless and known as UV transparent compounds. 2. π------->   π* transitions     The unsaturated hydrocarbons containing double or triple bond shows this type of transition. The π ---->π* bands appear at 180-190nm in the case of aliphatic compounds and at 200-210nm in the case of simple aromatic compounds.  Eg: Ethene-190nm, 1,3-butadiene – 217nm, 1,3,5-hexatriene – 247nm, Benzene- 255nm 3. n------->    π* transitions These transitions are observed in aldehydes and ketones which contain the C=O group which has both π electrons and non

 U-V VISIBLE SPECTROSCOPY  UV-Vis spectrum results from the interaction of EM radiation in the UV-Vis region with atoms and molecules. The UV radiation region extends from 200nm to 400nm and the visible region extends from 500nm to 800nm. Organic compounds, inorganic compounds, and coordination compounds fall in the UV-Vis spectrum. THEORY The absorption of radiation in the UV-Vis region of the spectrum is dependent on the electronic structure of the absorbing species.  When a photon of a given wavelength interacts with a molecule it may cause a transition among the electronic energy levels if its energy matches with the difference in the energies of these levels. A given electronic energy level has a number of vibrational energy levels in it and each of the vibrational energy levels has a number of rotational energy levels in it. So along with the electronic transition, vibrational and rotational transitions also occur simultaneously. So electronic spectrum appears broad. Transitions

BEER LAMBERTS LAW   When a beam of monochromatic EM radiation is passed through an Absorbing solution of concentration (c), the rate of decrease in intensity(-dI) of radiation with a thickness of the solution (dx) is proportional to the intensity of the radiation (I) and concentration (c) of the solution. -dI/dx ∝ Ic  -dI/dx = kIc  -dI/I =kcdx Beer Lambert's law gives the linear relationship between the absorbance of EM radiation and the concentration of an absorber. A = εcL A is the absorbance c is the concentration L is the path length Ε is the molar extinction coefficient

 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 THINKING Identify ne

 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 of the metal in th

 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  Metal is in con