Thermodynamics of the Dissolution Borax

Thermodynamics of the Dissolution of Borax Lina Jawadi Objectives * Study a system of salt and wet solution. * Determining a variety of beta thermodynamics quantities from the solubility information at various temperatures. Background The salt and pee supply solution in this taste has relatively simple solubility sense of balance of borax in water. Na2B4O7 . 10 H2O 2Na + + B4O5(OH)42- + 8H2O This reaction is an proportionality process and 8 water molecules from the hydrated salt are lost to the reaction medium. The equilibrium constant font for this reaction isK = Na+2 B4O5(OH)42- H2O8 Na2B4O7 . 10 H2O In this experiment we will always make sure there is some substantiality borax remaining in the examine pastiche before removing some of it to analyse it. Therefore, we can assume that the concentration of solid borax is constant. In addition, the water molecules which were originally part of the boraxs crystalline matrix is lost to the sample mixture however, it doesnt si gnificantly affect the concentration of the water. The equilibrium constant expression can now be simplified to become K = Na+2 B4O5(OH)42-The commencement ceremony equilibrium expression and the balanced solubility equilibrium reaction give up us to express either borate ion or sodium ion in basis of the other. So, it is possible to determine the constant in terms of either ion. later substituting borax ion in place of the sodium ion, (Na+ = 2 B4O5(OH)42- , K = (2 B4O5(OH)42- )2 * B4O5(OH)42- ) we exit K = 4 B4O5(OH)42-3 . Finding the concentration of borate ion in any(prenominal) sample at any given temperature gives us the solubility product at that temperature. Equipment * 5mL pipet * Test tubes * Marker * Hot plate * 250 mL beaker * flask Electric balance Procedure 1. Using the pipet add 5mL of distilled water to 10 streamlet tubes. 2. Mark the level with the marker and pour the water out. Mark the test tube with the assigned temperature. 3. Weigh 30-32g of solid sodium borate decahydrate (borax) in a 250 mL beaker and then add 150 mL of water. 4. Place the mixture on a sizzling plate, but outweart allow its temperature to exceed 50oC. 5. After all the borax dissolves, add to a greater extent and let the temperature reach 45oC. 6. Once it starts slightly exceeding 45oC, remove it from the hot plate and place instead a beaker modify with 150 mL of distilled water. . Continue stirring the mixture until it reaches the desired temperature. 8. Quickly pour 5 mL of the mixture in two test tube without transferring any solid borax. (record the temperature before and after the transfer. ) 9. When the water bath reaches 45oC, place the test tube in it until precipitation of borax has dissolved. 10. In a flask with 50-75 mL of water and 10 drops of bromocresol green indicator, add 125 mL of the borax solution. 11. onwards titrating the borax with acid make sure that it has a naughty color.Using buret filled with 50 mL oh HCl, add the acid to the borax until it reaches the endpoint, which is when the solution turns from a blue color to a yellow. Record the initial and final volume. (For calculations find the moles of borax using the volume of HCl and its molarity. Then find the solubility product constant and eyepatch the ksp vs. (1/t) graph and from it obtain the values of ? H and ? S. Make sure the temperature is in kelvin when doing the calculations. Finally, find the value of ? G using both equations and dapple the ? G vs. time graph. )