Thermodynamics of Potassium Nitrate

# Thermodynamics of Potassium Nitrate - JABATAN KEJURUTERAAN...

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JABATAN KEJURUTERAAN MEKANIK UNIVERSITI MALAYA SEM 2 SESI 2008/2009 TERMODINAMIK BAHAN KMEB1202 AMALI 1 The thermodynamics of Potassium Nitrate (KNO 3 ) PURPOSE To measure the solubility of potassium nitrate in different volume of water at elevated temperatures. To calculate the equilibrium constant K sp , Gibbs free energy change ΔG, enthalpy change ΔH and entropy change ΔS for potassium nitrate dissolving in water. BACKGROUND Solubility Equilibrium When potassium nitrate (KNO 3 ) dissolves in water, it dissociates into potassium ions ( 29 + K and nitrate ( 29 - 3 NO . Once sufficient quantities of + K and - 3 NO are in solution, however, the ions recombine into solid KNO 3 . Eventually, for every pair of ions that forms, another pair recombines. As a result, the concentrations of the ions remain constant; we say the reaction is at equilibrium. This solubility equilibrium of KNO 3 is shown in Eq. 1 below. where the opposing arrows indicate that the reaction is reversible. We call this system, where undissolved solid is in equilibrium with its dissolved ions, a saturated solution. We can describe the saturated solution with its fixed concentrations of ions with an equilibrium constant expression. Eq. 2 defines the equilibrium constant K sp for KNO 3 dissolving in water. The sp stands for solubility product and the square brackets around the ions symbolize molar concentration (M or mol/L). The equation shows that the equilibrium constant not only is concerned with solubility but also is expressed as a product of the ions molarities. The value for

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## This note was uploaded on 04/04/2012 for the course DEPARTMENT KEB taught by Professor Haseeb during the Summer '11 term at University of Malaya.

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Thermodynamics of Potassium Nitrate - JABATAN KEJURUTERAAN...

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