CHM171L Report 2 - CHM171L / A11 Physical Chemistry...

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CHM171L / A11 Physical Chemistry Laboratory 2 1 st Quarter S.Y. 2010-2011 Thermodynamics of Mixtures: Determination of Partial Molar Enthalpy Calderon, Edna 1 , Palomaria, Ralph Matthew 2 ,Pineda,Jermaine Marianne 2 , Regulacio, Anna Rafaela 2 1 Professor, CHM171L/A11, School of Chemical Engineering, Chemistry and Biotechnology, Mapua Institute of Technology; 2 Student, CHM171L /A11 , School of Chemical Engineering, Chemistry and Biotechnology, Mapua Institute of Technology ABSTRACT This experiment is on the subject of thermodynamics of mixtures, particularly on the determination of partial molar enthalpy. A partial molar property is a thermodynamic quantity which indicates how an extensive property of a solution or mixture varies with changes in the molar composition of the mixture at constant temperature and pressure , or for constant values of the natural variables of the extensive property considered. To determine the effect of concentration of the different components of the mixture on the molar enthalpy of the solution and to evaluate the partial molar enthalpy of the different components of the mixtures are the objectives of this experimentation. Here, Ammonium chloride served as the solute and distilled water was the solvent. It was observed that as the composition of the components of the mixture changes, the molar enthalpy of the solution varies in effect. INTRODUCTION A partial molar quantity is the change in the considered extensive quantity when an infinitesimal amount of substance is added to the system at constant temperature, pressure and amounts of all other constituents of the system divided by the added amount. THEORY: When one mixes 1 mole of H 2 O (which has a molar volume of 18 cm 3 ) with a large quantity of ethanol, the volume increase observed is not 18 cm 3 . This simply indicates that extensive properties of solutions (such as volume, free energy, enthalpy, etc.) cannot be truly added when pure components are mixed. The surrounding of a molecule is very important in determining how much volume it will occupy, how much energy it will have, etc. So, a H 2 O molecule surrounded by other molecules behaves quite differently from a H 2 O molecule surrounded by ethanol molecules. The quantity of a substance in each environment is known as the partial molar quantity of that substance in that given environment. The laws of thermodynamics and the
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This note was uploaded on 07/31/2011 for the course CHE-CHM-BT CHM171L taught by Professor Calderon during the Spring '11 term at Mapúa Institute of Technology.

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CHM171L Report 2 - CHM171L / A11 Physical Chemistry...

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