formal Report
Simultaneous Determination of Several Thermodynamic Quantities:
K, ∆G°, ∆H°, and ∆S°
Submitted by: Feldan P. Villarta
Submitted to: Mrs. Gloria Jesusa D. Baltazar
Chemistry 73 (Laboratory)
August 11, 2014
Simultaneous Determination of Several Thermodynamic Quantities:
K, ∆G°, ∆H°, and ∆S°
Feldan P. Villarta
I. INTRODUCTION The solubility product constant, Ksp , is the equilibrium constant for a solid substance dissolving in an aqueous solution. It represents the level at which a solute dissolves in solution. A more a substance dissolves, the higher the Ksp value it has. In this experiment, a system of a sparingly soluble salt in water is studied. From the solubility information at various temperatures, the changes in standard enthalpy, standard entropy, and standard free energy were established.
II. THEORETICAL BACKGROUND The reaction that is studied in this experiment is the dissolution of borax in water. “Borax” is a naturally occurring compound; it is in fact the most important source of the element boron, and it has been used for many years as a water softening agent. Borax is a rather complicated ionic salt which has the chemical formula Na2B4O7•10H2O (Petrucci, 2007). When it dissolves, it dissociates as follows:
Na2B4O7 • 10H2O(s) 2Na(aq) + B4O5(OH)42(aq) + 8H2O(l) rnx (1)
The solubility product expression for this system is written below.
Ksp = [Na]2 [B4O5(OH)42] (2)
To determine a value for the solubility product, a method must be found to assay either the amount of sodium ion, or borate ion, in the sample mixture. The original equilibrium expression, and balanced solubility equilibrium reaction, leads to a convenient way to express either ion in terms of the other, so that it is possible to define Ksp in terms of either the concentration of sodium ion, or concentration of borate ion (Chang, 2010). A series of
K, ∆G°, ∆H°, and ∆S°
Submitted by: Feldan P. Villarta
Submitted to: Mrs. Gloria Jesusa D. Baltazar
Chemistry 73 (Laboratory)
August 11, 2014
Simultaneous Determination of Several Thermodynamic Quantities:
K, ∆G°, ∆H°, and ∆S°
Feldan P. Villarta
I. INTRODUCTION The solubility product constant, Ksp , is the equilibrium constant for a solid substance dissolving in an aqueous solution. It represents the level at which a solute dissolves in solution. A more a substance dissolves, the higher the Ksp value it has. In this experiment, a system of a sparingly soluble salt in water is studied. From the solubility information at various temperatures, the changes in standard enthalpy, standard entropy, and standard free energy were established.
II. THEORETICAL BACKGROUND The reaction that is studied in this experiment is the dissolution of borax in water. “Borax” is a naturally occurring compound; it is in fact the most important source of the element boron, and it has been used for many years as a water softening agent. Borax is a rather complicated ionic salt which has the chemical formula Na2B4O7•10H2O (Petrucci, 2007). When it dissolves, it dissociates as follows:
Na2B4O7 • 10H2O(s) 2Na(aq) + B4O5(OH)42(aq) + 8H2O(l) rnx (1)
The solubility product expression for this system is written below.
Ksp = [Na]2 [B4O5(OH)42] (2)
To determine a value for the solubility product, a method must be found to assay either the amount of sodium ion, or borate ion, in the sample mixture. The original equilibrium expression, and balanced solubility equilibrium reaction, leads to a convenient way to express either ion in terms of the other, so that it is possible to define Ksp in terms of either the concentration of sodium ion, or concentration of borate ion (Chang, 2010). A series of
References: Brown, T. et.al. (2012). Chemistry: The Central Science. 12th ed. United States of America: Pearson Education, Inc. Chaka, G. & Madhugiri S. (n.d.) Determination of Thermodynamic Quantities for a Chemical Reaction Chang, R. (2010). Chemistry. 10th ed. 1221 Avenue of the Americans, New York: McGraw- Hill Companies, Inc. Petrucci, Ralph H., et al. General Chemistry: Principles and Modern Applications. Upper Saddle River, NJ: Prentice Hall 2007. Weisstein, E. W. (2014). Roundoff Error. Retrieved July 22, 2014 from the world wide web: http://mathworld.wolfram.com/RoundoffError.html Experiment 17. Thermodynamics of Borax Solubility Chemistry 212 Lab: Simultaneous Determination of Several Thermodynamic Quantities: K, ∆G°, ∆H°, and ∆S°