Chemistry Buddies

  BUTLER- VOLMER EQUATION: Dependence of electrochemical reaction rate on overpotential. The electrode/solution current may be cathodic or anodic according to the flow of electrons which can measure the sign of overpotential i.e deviation from the equilibrium condition the two partial current densities are equal in magnitude and opposite in direction.i.e      η(overpotential) = ∆φ-∆φe , ∆φ = potential difference observed by adjusting the outside potential source for the change in current flow.     ∆φe = potential difference at equilibrium There will be polarization i.e potential variation from equilibrium     icath = ianod , at equilibrium. If icath = ianod = i 0  r1 = rate of M n+ formation (i cath)  r2=rate of M formation ( i anod)   i 0 = exchange current density                  icath > ianod          r2>r1, if E0 for (M n+ /M) at equilibriu...

  Thermodynamics explaination of electrified interface-Lippmann equation 1.Consider electrode/ electrolyte interface as closed system where no matter leaves or enter in it, then    dU =TdS-W TdS=Q= Heat produced/supplied reversibly W= Work carried out reversibly.  2.Again consider it as an open system, matter can exchange between and surrounding .Let us introduce a mol of i species , the chemical potential on the system is μi  dni is the change of the number of moles, then work done = - μidni dμ= TdS-W-∑μidni ∑μidni= work done required to expel dni of species i The work done in the metal/solution interface (MI/S) are due to (a) volume expansion PdV (b) increase of surface area dA , the corresponding increase of interfacial tension ν. dA 3. Changing the external source of electricity for altering the charge on the metal by dq' M is  MI∆S φ.dq'M MI∆S φ=V, MI∆S φ= interfacial tension, V=applied potential dU=TdS-PdV- νdA - MI∆S φ.dq'M - ∑μidni…….(1) Each ter...

 See previous notes in below link https://www.chemistrybuddies.in/2021/06/organic-photochemistry.html?m=1 Photochemical Processes: • 6.Certain chemicals change their color when exposed to suitable radiation and reverse when the radiation source is removed. These are known as photochromic materials. A well known example is spiropyrans.Such materials are used in photochromic sunglasses. • 7. In photography, it is the photo reduction of silver ions into silver metal ,which is the main phenomenon.Colour photography is based on the same chemistry, where silver halide is in superimposed gelatin layers, each sensitive to only one of the primary colors. • 8.Newborn babies, particularly those born prematurely, often suffer from jaundice or hyperbilirubinemia.This is because they have difficulty in excreting bilirubin formed through metabolism of heme.Bilirubin is toxic and high conc. can induce brain damage or even death. Only treatment of neonatal hyperbilirubinemia is the exposure to ligh...

Organic Photochemistry Part I Learning Objectives:   In this unit we shall learn about the  i) Basic Principles of Photochemistry. ii). Several photophysical processes . iii). Photochemical reactions of a few classes of organic compounds. INTRODUCTION Classical Chemistry : It involves the reactions of molecules in their ground electronic states. Photochemistry : It involves the reactions of molecules in excited electronic states.  Organic photochemistry is the study of reactions that occur through excited states of organic molecules produced by the absorption of electromagnetic radiation in the UV-Vis region. Classical Chemistry & Photochemistry There are a few advantages of photochemistry over classical chemistry. 1.In photochemistry selective activation of individual reactant in a mixture of number of reactant is possible. 2.There is an activation energy requirement for every chemical reaction. However if the activation energy is very high, the desired reaction ca...

CITRAL , 3,7-Dimethyl-2,6-octadien-1-a l, (C 10 H 16 O): •      Citral is the most important member of the acyclic monoterpenoids. •          It is found in oil of orange ( 6 to 7 %) and in citronella oil. •          It is pale yellow liquid having boiling point 238⁰C.    The structure of Citral is elucidated from the following:      i.             Molecular formula of Citral is C 10 H 16 O.   ii.             Citral reacts with bromine to form a tetrabromide derivative. This indicates the presence of two C-C double bonds in the citral   molecule. iii.             Citral reacts with hydroxylamine to form an oxime. It also adds sodium bisulfite.   These reactions indicate the p...

              Molecular Orbital Theory    The goal of molecular orbital theory is to describe molecules in a similar way to how we describe atoms, that is, in terms of orbitals, orbital diagrams, and electron configurations.                 Forming a Covalent Bond n Molecules can form bonds by sharing electron n Two shared electrons form a single bond n Atoms can share one, two or three pairs of electrons n forming single, double and triple bonds n Other types of bonds are formed by charged atoms (ionic) and metal atoms (metallic). Atomic and Molecular Orbitals: n Orbital Mixing. n When atoms share electrons to form a bond, their atomic orbitals mix to form molecular bonds. In order for these orbitals to mix they must: n Have similar energy levels. n Overlap well. n Be close together. Important P...