# boraxlab - Simultaneous Detemination of several...

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Simultaneous Detemination of several Thermodynamic Quantities: K, Delta G, Delta H, and Delta S Connie Jamieson 11/3/2011 Instructor: Tiffany Ha Chemistry 212 section 205 Lab partner: Elizabeth Ho Calculations: Trial 1: Moles HCl: (0.250 x 0.0042) = 0.0011 mols of HCl Moles of Borax: 0.0011mols HCl ( 1mol borax/2mols HCl) = 5.3 x 10 -4 mols borax 5.3 x 10 -4 mols borax/0.0050L borax solution used = 0.011M borax Ksp= 4(0.011M) 3 = 0.0046 M 3

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∆G= -(8.314J/mol∙K) x (303K) x ln(0.0046M 3 ) = 13557 J/mol Refer to figure 1: lnKsp=-11444(1/T)+31.8 ∆H (enthalpy) = -11444/8.314= -13542.1 J ∆S (entropy) = 31.8/8.314= 3.83 J/K Table 1:Trial 1 Borax Titration Group HCl (M) Temp (K) Volume Borax used (L) Volume of HCl used (L) Moles HCl (mols) Mole Borax (mols) Concentration of Borax (M) Ksp M 3 1 0.250 308 0.005 0.0033 0.00083 0.00041 0.083 0.0022 2 0.250 298 0.005 0.0060 0.0015 0.00075 0.15 0.014 3 0.250 303 0.0048 0.0016 0.00040 0.00020 0.042 0.00029 4 0.250 298 0.005 0.0020 0.00050 0.00025 0.050 0.00050 5 0.250 313 0.005 0.0105 0.0026 0.0013 0.2625 0.072 6 0.250 295 0.005 0.0040 0.0010 0.00050 0.10 0.0040 7 0.250 303 0.005 0.0042 0.0011 0.0005 3 0.11 0.0046 8 0.250 318 0.005 0.003 0.00070 0.00035 0.070 0.0014 9 0.250 295 0.0051 0.0025 0.00063 0.00031 0.061 0.0009
Table 2: Trial 2 Borax Titration and averages of data Grou p Tem p (K) Volume of HCl used (L) Moles HCl (mols) Volume Borax used (L) Mole Borax (mols) Conc. of Borax (M) Ksp M 3 Average Ksp M 3 ∆G (J/mol) average 1 308 0.0031 0.00078 0.005 0.00039 0.078 0.0019 0.0021 15845.6 2 298 0.0040 0.0010 0.005 0.00050 0.10 0.0040 0.0088 11740.5 3 303 0.0016 0.00040 0.0049 0.00020 0.041 0.00027 0.00028 20602.3 4 298 0.0011 0.00028 0.005 0.00014 0.028 8.3E-05 0.00029 20167.8 5 313 0.0108 0.0027 0.005 0.0014 0.27 0.079 0.076 6721.9 6 295 0.0026 0.00065 0.005 0.00033 0.065 0.0011 0.0025 14647.0 7 303 0.0043 0.0011 0.005 0.00054 0.11 0.0050 0.0048 13450.1 8 318 0.0060 0.0015 0.005 0.00075 0.15 0.014 0.0074 12958.6 9 295 0.00175 0.00044 0.0051 0.00022 0.043 0.00032 0.00062 18122.8 Figure Conclusion: The purpose of this lab was the study of a sparingly salt. The solubility information was determined at various temperatures. The following thermodynamic quantities were determined the change in standard enthalpy, standard entropy, and standard free energy. The equation for this lab yields the following reaction when the borate ion was titrated with HCl:

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B 4 O 5 (OH) 4 -2 (aq) + 2HCl + 3H 2 O ↔ 4B(OH) 3(aq) + 2Cl - The equation for the equilibrium of borax is as follows: Na 2 B 4 O 7 ∙10H 2 O (s) ↔ 2Na + (aq) + B 4 O 5 (OH) 4 -2 (aq) + 8H 2 O (l) This equation is written as an equilibrium process. The eight water molecules from the hydrated salt will be lost in the reaction medium.
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