Temperature of the water bath was measured again 5

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temperature of the water bath was measured again. 5. The solution in the 250-mL beaker was allowed to cool to approximately 37 °C to 33 °C . 1
6. The sampling procedure for temperature close to “35 °C ”, “25 °C ”, “15 °C and “5 °C ” was repeated from step 1 to step 4. Part D: Titration of the Borax Sample Solution 1. A 50-mL burette with HCl solution was rinsed and filled until there are no air bubbles along the inside surface of the burette. 2. The 5-mL sample was poured into a clean conical flask. The test tube was rinsed with several portions of the warm rinsed water. The rinsed solutions were transferred to the flask and the mixture was swirled. 3. Three drops of bromocresol green indicator were added to the flask. 4. The solution was titrated with the standardized HCl until the solution turns from blue to yellow. 5. The above procedure was repeated for all the other borax sample. 2
Results and Calculations: Test tube Average volume of HCl used (mL) Number of moles of HCl (mol) [B 4 O 5 (OH) 4 2- ] K sp ln K sp T(K) 1/T (1/K) 45 C 2.35 1.18 x10 -3 0.118M 6.57x10 -3 -5.03 318 3.14x10 -3 35 C 2.00 1.0 x10 -3 0.100M 4.0x10 -3 -5.52 308 3.25x10 -3 25 C 1.50 7.5 x10 -4 0.075M 1.69x10 -3 -6.38 298 3.36x10 -3 15 C 1.50 7.5 x10 -3 0.075M 1.69x10 -3 -6.38 288 3.47x10 -3 5 C 1.35 6.75 x10 -4 0.068M 1.26x10 -3 -6.68 278 3.60x10 -3

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