States of Matter — DU B.Sc (hons) Chemistry Previous Year Question Papers

5. (a) What are the seven crystal systems? Describe each system in terms of its axial lengths (a,b,c) and interaxial angles  , ,   . (b) What is the effect of molecular mass on the Maxwell Boltzmann distribution curve at a constant temperature? (c) Explain various types of point defects in crystals with diagrams and suitable examples. 6. (a) Briefly describe (i) Bragg's Law of X-ray diffraction, (ii) Law of rational indices. (b) Define interplanar spacing for a crystal lattice and write the equation relating to interplanar spacing dhkl and miller indices for a cubic lattice. Calculate the interplanar spacing of planes with miller indices (121) in a cubic crystal of edge length 1.5 Å (c) What is fundamental principle on which powder X-ray diffraction technique works? Explain powder diffraction pattern of NaCl with diagram. (5, 5, 5) Attempt four questions 1. Attempt the following questions briefly: (Any five) In a graph of compressibility factor Z. versus Pressure, the curve for NH3 shows a much deeper dip than the curve for N2 at the same temperature. Explain what a 'deeper dip' signifies regarding the nature of the gas and its intermolecular forces. (b) What is the ratio of V rms of H2 and O2 at the same temperature (c) Write an expression for Van der Waals equation for real gas. Under what conditions does a Van der Waals gas behave like an ideal gas? (d) What is 'Excluded Volume'? How is it related to the actual volume of molecules? (e) Why do raindrops assume a spherical shape? (f) What is Law of Constancy of interfacial angles? 2. (a) Calculate the Miller indices for the following planes: (b) Derive an expression for the pressure exerted by an ideal gas as given by the kinetic gas equation and also find kinetic energy of the system. (c) Define "Boyle Temperature" Tb Write its mathematical expression in terms of Vander Waals constants. How does gas behaviour differ above and below this temperature? 3. (a) Discuss the significance of the "Horizontal Portion" in the Andrew isotherms below 31.1°C Why does it disappear at the critical point? (b) Write the expressions for the critical constants Tc, Pc &. Vc Show that the critical compressibility factor Zc is equal to 0.375. (c) A stalagmometer produced 40 drops of water and 60 drops of a liquid. The density of the liquid is 0.85g/cm3 and that of water is 1.0 g/ cm3 If the surface tension of water is 72.0 dynes/cm at 20°C, calculate the surface of the liquid. (5,5,5) 4. (a) Starting from Poiseuille's equation, derive the expression for the determination of the relative viscosity of a liquid using an Ostwald Viscometer. Explain all the terms involved. (b) The flow time for water at 20°C is 80 s and 240 s for an unknown solution, their densities are 1.0 g/cm³ and 0.9 g/cm³ respectively. If the absolute viscosity of water is 1.002cP (centipoise), calculate the absolute viscosity of an unknown solution at 20°C. (c) Define the three speeds originating from