152 Exp 4 Report - Points to assign EXPERIMENT 4:...

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Points to a Total Points = 60 PURPOSE AND METHOD 4 4 DATA AND CALCULATIONS A. Standardization of NaOH Run 1 Run 2 Mass of KHP 0.13 0.12 moles KHP 0.000641 0.000592 Initial buret reading, mL 0.19 0.56 Final buret reading, mL 6.01 6.10 mL NaOH titrated 5.82 5.54 L NaOH titrated 0.01 0.00554 [NaOH], moles/L 0.110 0.107 Average, [NaOH] 0.109 M 3 pts 3 1 pt 1 Table 1: NaOH Standardization How are the solubility products (K sp ) of KHP at various temperatures determined? ( 4 pts ) The solubility products (Ksp) of KHP is determined by titrating various solutions at different temperatures with standardized NaOH. Since we know the concentration of the NaOH and we know that NaOH and KHP will react 1:1, we know that the number of moles of NaOH and KHP are equal the equivalence point. Therefore, we know the number of moles of K+ and HP- and can calculate the concentration of each. From those two concentrations we can determine Ksp as [HP-]^2. How is K sp in a saturated solution of KHP in 0.50 M KCl determined? ( 4 pts ) Ksp in a saturated solution of KHP in KCl is determined by finding the concentration of K+ and HP- separately and multiplying them together (Ksp = [K+][HP-]). [K+] was found by using 5 standard solutions with known concentrations and measuring their intensities using the flame emitter. Using the 5 standard solutions and their intensities we were able to find an equation for calculating [K+] based on the measured intensity value. We then measured the intensity of a diluted solution of KHP in KCl and calculated [K+] using the y = mx + b equation we found. [HP-] was found using titration. We titrated 3 mL of the solution in a known concentration of NaOH. At the equivalence point, the mmoles of NaOH equals that of HP-. The mmoles NaOH was calculated using the amount added and its known concentration value. The concentration of HP- was then found by dividing the mmoles of HP- by the mL of KHP we originally added. EXPERIMENT 4: THERMODYNAMICS II THE TEMPERATURE DEPENDENCE OF THE SOLUBILITY PRODUCT, HEAT OF SOLUTION, AND ENTROPY OF SOLUTION OF POTASSIUM HYDROGEN PHTHALATE By signing below, you certify that you have not falsified data and that you have not plagiarized any part of this lab report. Signature:
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This note was uploaded on 04/07/2008 for the course CHEM 152 taught by Professor Chiu during the Winter '08 term at University of Washington.

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152 Exp 4 Report - Points to assign EXPERIMENT 4:...

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