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Chemistry Zone
	Chemistry This is an attempt to simplify the chemical principles in order to make them understandable. The equation and formulas are systematized and the figures have been made self explanatory and illustrative. This is a “Ready Reckoner” to solve problems and an earnest attempt to make the subject more comprehendible to the students. List of Topics · ATOMIC STRUCTURE · FUNDAMENTAL LAWS AND CHEMICAL ARITHMETIC · GASEOUS STATE · SOLUTION CHEMISTRY · CHEMICAL EQUILIBRIUM · CHEMICAL KINETICS · CHEMICAL ENERGETICS · ELECTRO CHEMISTRY · CHEMICAL BONDING · OXIDATION AND REDUCTION · ANALYTICAL CHEMISTRY · ORGANIC CHEMISTRY ATOMIC STRUCTURE 1) Atom consists of fundamental particles such as electron, proton and neutron. 2) Electron is negatively charged with mass 9.109535 x 10-28g and charge 4.602 x 10-19 coulombs. 3) Proton is positively charged particle with mass 1.6735 x 10-24 gram. 4) Neutron is a neutral particle with mass 1.6750 x 10-24 gram. 5) Atomic mass unit (amu) is defined as 1/12 the mass of 6C12 isotope. 1 amu = 931.5 MeV = 1.66 x 10-27 kg. 6) The 3 dimensional region where there is maximum possibility of finding an electron is called Orbital. The different orbital in an atom are s,p,d,f 7) Quantum numbers give the address of an electron. There are 4 different types of quantum numbers : i) Principal quantum number denotes the energy level designated by the letter ‘n’ ii) Orbital quantum number also called as angular momentum or azimuthal quantum number denotes the sub shell to which the electron belongs shown by the letter ‘l’. The values of ‘l’ range from 0 to (n – 1). If ‘l’ = 0 = s orbital, ‘l’ = 1 = p orbital, ‘l’ = 2 = d orbital ‘l’ = 3 = f orbital iii) Magnetic quantum number denotes the orientation of orbitals in space. It is shown by the letter ‘m’. The values of ‘m’ = + l to – l iv) Spin quantum number denotes the spin of the electron. The permitted values of s = + ½ and – ½ 8) The maximum number of electrons present in a main energy level = 2n2 9) The electrons are filled according to Aufbau Principle in the increasing order of there energy. The relative energies of orbitals are as follows : 1s < 2s < 2p < 3s < 3p < 4s < 3d < 4p < 5s < 4d < 5p < 6s < 4f < 5d < 6p < 7s < 5f < 6d < 7p < 8s ……and so on. 10) The Planck’s has the value 6.626 x 10-27 ergs sec of 6.626 x 10-34 Js. 11) The value of Rydberg constant is 109677 per cm. IMPORTANT RELATIONS FOR NUMERICAL PROBLEMS 1) Relation between velocity (c ), wavelength ,frequency and wave number : a) Velocity = Frequency x Wavelength b) Wave Number = 1/ wave length c) wave number = frequency / velocity. 2) The relation between Energy, frequency and wavelength : Energy= Planck’s constant x frequency or Energy = Planck’s constant x velocity / wave length 3) Energy of an electron in unielectron atomic system = En = - 2 pi 2 me4z2 / n2h2 4) Wave number = R[1/n12 – 1/n22] where R is Rydberg constant and n1 and n2 are different lines in the hydrogen spectrum. For lyman series n1 = 1 and n2 = 2,3,4,5 ….. Balmer series n1 = 2 and n2 = 3,4,5……………. Paschen series n1 = 3 and n2 = 4,5,6………….. Brackett series n1 = 4 and n2 = 5,6,7…………… Pfund series n1 = 5 and n2 = 6,7,8…………….. 5) deBroglie equation : wave length = Planck’s constant / mass x velocity. FUNDAMENTAL LAWS AND CHEMICAL ARITHMETIC 1) Laws of conservation of mass : The total weight of products = Total weight of the reactants in a chemical process 2) Law of definite proportion : The same chemical compound irrespective of its method of preparation always contains the same elements combined in a definite proportion by weight 3) Law of multiple proportion : When 2 element combine to form two or more compounds then the different weights of one element combining with a fixed weight of other bear a simple integral ratio 4) Law of Reciprocal Proportions : Two elements A and B would combine in the ratio of the weights or in simple multiples of the weights in which they separately combine with the fixed weight of the third element C. These weights are called equivalent weight. Atomic weight = Equivalent weight x Valency 5) Molecular weight of a gas = 2 x Vapour density 6) Avogadro’s Number : it is number of atoms or molecules present in one gram atom or one gram mole of a substance. It is equal to 6.023 x 1023 atoms or molecules Multiply Multiply Number of < ------------ Number of ----------------- > Mass 6.023 x 1023 Mole of a Molecular Mass of Particles ---------- > Substance < --------------- Substance Divide Divide 7) Number of molecules = weight of the substance x Avogadro’s Constant / gram molecular weight of the substance 8) Number of molecules = volume of gas in litres x Avogadro’s Constant / 22.4 litres 9) Balancing of chemical equation should be done by counting the number of atoms that has reacted and equal number of atoms in the products should be present. GASEOUS STATE 1) An ideal gas obeys the gas laws like Boyle’s Law, Charles Law and Avogadro’s Law 2) At absolute zero (-273 degree centigrade) the volume of any gas and the total kinetic gas is zero 3) The universal gas constant R = 8.314 J / K / mole or 0.0821 L atm / K / mol. 4) The pressure due to water vapour at a given temperature is known as aqueous tension or saturated water vapour pressure 5) Pressure of dry gas = Total pressure – aqueous tension IMPORTANT RELATIONS · Boyle’s Law equation – PV = Constant · Charles Law equation – V / T = Constant · Avogadro’s Law - V is proportional to n · Ideal gas equation – PV = nRT · General gas equation – P1V1 / T1 = P2V2 / T2 · Kinetic gas equation – PV = 1/3 mnc2 · Gaylussac’s Law – P1 / T1 = P2 / T2 · Graham’s Law of diffusion – r1 / r2 = Square root of M2 / M1 = Square root of d2 / d1 · Van der Waal’s equation – [P + an2 / v2] [V-nb] = nRT · Molar mass and density – d = PM / RT · Average kinetic energy of gas – KE = 3 / 2 kT · Root mean square velocity – RMS = square root of 3RT / M SOLUTION CHEMISTRY Expressing concentration of solution: · Weight percentage = Grams solute / Grams solute + Grams solvent x 100 · Volume percentage = Volume of solute / volume of solution x 100 · No of moles = Weight in grams / molecular weight = volume in litres / 22.4 at STP (Standard Temperature 273 K, Pressure 1 atm) for gases · Number of millimoles = 1000 x weight in grams / mol.wt = Molarity x Volume (ml) · Molarity (M) = weight of solute / gram molecular weight x 1000 / volume in ml · Molality (m) = Strength in grams per 1000 grams of solvent / gram molecular weight of the solute OR m = specific gravity x % strength / 100 x 1000 / volume in ml · Normality = N = % strength x specific gravity x 10 / equivalent weight OR · N = weight of solute / gram equivalent weight of solute x 1000 / volume of solution in ml OTHER IMPORTANT RELATIONSHIPS · PV = w / m RT where P is pressure V = volume, w = weight in grams, m = molecular weight , R = gas constant, T = temperature · Raoult’s Law : Po – P / Po = n / n + N where n is the number of moles of the solute, N number of moles of solvent, Po is the vapour pressure of the solvent, P is the vapour pressure of the solution. · n = w / m · For isotonic solutions w1 / m1V1 = w2 / m2V2 · Ebulioscopic constant = Kb = RTO2 / 1000 lv where TO is the boiling point of pure solvent and lv is the latent heat of vaporization of one mole of solvent in grams. · Elevation in boiling point = Tb = Kb x w1 / w2 x m1 x 1000 where w1 and m1 are weight and molecular weight of solute and w2 = weight of the solvent · Depression in freezing point = Tf = Kf x w1 / w2 x m1 x 1000 · Cryoscopic constant Kf = RTf square / 1000 x lf · Partial Pressure of a component = vapour pressure of the component x mole fraction · Depression in freezing and osmotic pressure = Tf = 1000 x Kf x p / d x R x T where p = osmotic pressure, d = density · Vanthoff factor i = observed colligative property / normal colligative property · Degree of dissociation Alpha = i - 1 / n – 1 where n is the number of ions produced by complete dissociation of 1 mole of the substance CHEMICAL EQUILIBRIUM · Equilibrium is defined as the point at which the rate of forward reaction is equal to the rate of backward reaction. · Chemical equilibrium is dynamic in nature. · Active mass is molar concentration of the substance.Active mass is unity in a solid.(equal to one) · Active mass = mass of reactant (g)/ molecular mass/ volume in Litres. · Law of mass action states that rate of a chemical reaction is directly proportional to the product of active masses of the reacting substance. · For a reaction A + B -àC + D , the equilibrium constant Kc =[C] [D]/[A][B], each reactant raised to the power of its coefficient in the balanced chemical equation · For Gaseous reactions the concentration of the reactants and products are expressed in terms of partial pressure and the equilibrium constant is expressed as KP = [PC] [PD] / [PA] [PB], each term raised to a power equal to its coefficient in balanced chemical equation. · Lechatelier’s Principle states that if a system in equilibrium is subjected to a change of temperature ,pressure or concentration,then the equilibrium shifts in such a way that the effect of the changes is nullified. · During melting of ice the volume is decreased from 1.09 c.ccper gram to 1.01 c.c per gram. 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