Determination of the Ksp of Potassium Hydrogen Tartrate Lab Report, Lab Reports of Chemistry

Download Determination of the Ksp of Potassium Hydrogen Tartrate Lab Report and more Lab Reports Chemistry in PDF only on Docsity! Determination of the Ksp of Potassium Hydrogen Tartrate Assignment & Report Guidelines READING Experiment – Lab Handout Download Chemistry, 5th ed. by Silberberg: Section 19.3 PRE-LAB Prepare a standard prelab including the reaction studied (no abbreviations - put in appropriate context). Answers to Pre-Lab Questions (required): May be answered on the downloaded page and additional pages as needed. Show work. LAB REPORT Begin the lab report section on a new page of the lab notebook. The discussion and conclusion sections should be word-processed. Other parts of the report - calculations, etc. may be typed or written in the lab notebook. DATA: Present the original data, any excel or reorganized data tables (if appropriate). CALCULATIONS: Present the calculations of the following values for a single trial in the appropriate format, including labels, formulas, chemical reactions, etc. • [HT-] in the saturated solution as determined by titration. • [K+] in the saturated solution. • Ksp • Solubility of KHT in mol/L RESULTS: Summarize your three trials in a single table. • Include the information above for each trial. • Include your individual average Ksp, individual standard deviation for Ksp, and individual average solubility for KHT. • State the course average Ksp and standard deviation. DISCUSSION / ERROR ANALYSIS: • Briefly explain the theory and process of the experiment. • Comment on the precision of your titrations. Provide quantitative support of your statements. • Comment on the course precision in determining Ksp. Provide quantitative support of your statements. • Answer the following question: If some of the solid KHT passed through the filter due to a small tear and as a result was in the sample you titrated, how would that affect you calculated Ksp and solubility. Explain briefly. CONCLUSIONS: Provide standard conclusions. Answers to Post-Lab Questions (required): May be answered on the downloaded page and additional pages as needed. Show work. modular - faboratory program editor: H. A. Neidig EQUL 342 * program - in + chemistry Determination of the Solubility Product Constant of an Organic Salt prepared by Judith C. Foster, Bowdoin College Purpose of the Experiment | | Determine the solubility and solubility product constant of Potassium hy- drogen tartrate by titrimetry, Background Information A complete characterization of a chemical system in- volving substances dissolved in water includes study- ing the relevant equilibria. For the generalized chemi- cal reaction aA + DB == cC + dD, the equilibrium constant expression is: , ¢ = rer (Eo. 1) [AB In the case of an acid salt, such as sodium hydro- gen oxalate monohydrate (NaHCO, + HO} dissolving in water, an equilibrium is established among solid sa- dium hydrogen oxalate (NaHCO, ), sodium ion (Nat), and hydrogen oxalate ion (HC,0,7}, as shown in Equation 2. NaHC,0,(s} = Na*(aq) +HC,0, (aq) (Eq. 2) A quantitative characterization of this equilibrium would invoive determination of the amount of dis- solved NaHC,,0,(aq) in the presence of excess solid NaHC,0,(s). From Equation 2, we see that one mole of Na* and one mole of HC,0,- would be present in solution if one mole of NaHCO, dissolved. The molar ratio of dissociated NaHCO, to Nat in solution to HC,0,7 in solution would be 1:1:1, Thus, by determin- ing the concentration of HC.0,” in solution, we can find the amount of dissolved NaHC,0,. The concen- tration of HC2O,” in solution could be determined by the direct titration of the filtered solution with a stan- dard NaOH solution, as hydrogen oxalate ion is a weak acid. Since the molar ratio of HC,Q,7 to NaHC,0, is 1:1, the solubility of the acid salt will be numericaily equal to [HC,0,.7J. Asis the case with all equilibrium constant expres- sions, the amount of solid present does not affect the equilibrium concentrations, se jong as some solid is Present. The process involved in the dissolution of so- dium hydrogen oxalate is shown in Equation 2. The concentrations of all solids are assigned a value of 1.0, and therefore the concentrations of solids do not ap- Pear in the equilibrium constant expressions. The equilibrium constant for solids dissolving in a solvent is termed the solubility product constant, K,,. For the reaction in Equation 2, Kg, is written as shown in Equation 3. Keg = [Nat*YHC,04°1 (Eq. 3) The true Kop expression involves a correction for the behavior of ions in solution, Most ionic solutions are not dilute, and their behavior is not always ideal. The vaiue calculated using Equation 3 is a close approxi- mation of the actual K,,. name section date Pre-Laboratory Assignment 1. In.an appropriate source, read a discussion of the organic acid (gmm = 170.12). The equilibrium in- laboratory techniques used int acid-base titrations. volved is: CgHgO,CCOH(s) < ” "| 2, An experiment similar to the one in this module CeHs0,COO™(aq) + H*(aq) vas performed to determine the solubility and the Titrations using 1.14 x 1071M NaOH were performed, solubility product constant of gallic acid, a monoprotic and the following data were obtained. determination 1 2 3 temperature of solution, °C 20.2 20.4 20.1 volume of acid solution titrated, mL 25.00 22.00 20.10 volume of NaOH solution used, mL. 14.81 13.02 41.73 Calculate the following: number of moles of NaOH used ce number of motes of HYtitrated [H*] in acid solution [CgH,0,CO007] in acid solution a Ky ~ average K, solubility of acid in g per 100 mL chemistry handbook vaiue for 1.15 g per 100 mL solubility at 20 °C. 72 EQUL 342: Determination of the Solubility Product Consiant of a Salt Post-Laboratory Questions (Use the spaces provided for the answers and additional paper if necessary.) 1. Define the solubility ot a substance, 2. Convert your experimental solubility of KHT (in mol L-*) to g KHT per 100 mL. Compare this saiubility to the literature value, obtainable from a chemistry handbook, 3. Given the following solubility vs. temperature data for two compounds, answer the questions below. Compound A temperature, °C 25.0 . 26.7 48,0 - 63.0 solubility, mol L~! 5.60 5.81 7.27 Compound B temperature, °C 25.0 386 (434 49.0 | 52.0 | 56.2 | 60.0 | 67.2 T T solubility, mol ut 3.54 6.28! 747) 837 913 100 £11.22 § 12.6 {1} On graph paper, plot solubility vs. tempera: . ture for both compounds on one set of axes. — Ge. sua te clewsA 4 tela each | (2) Which compound's solubility is more affected “ by changes in temperature? Explain. name section date EQUL 342: Determination of the Solubility Product Constant of a Salt 73 4. Anexperiment similar to the one described in this The dissolved chloride in the filtered solution was module was performed to determine the solubility and quantitatively precipitated as AgCI by the addition of Solubility product constant of lead{ll) chloride (gmm = excess AgNO, solution. The solid AgC! was filtered 278.10}. The equilibrium involved is PbCip(s) > Pb?*(aq) + 2 C-(aq) from solution, dried, and weighed. The following data were obtained for three samples of the filtered, satu- temperature of solution, °C vaiume of PbCly solution analyzed, mL mass of dry AgCl, g Calculate the foltowing: number of moles af: AgGi(s) Ci ~tag) Pb? (aq) {Cl-] in PeCt, sotution, M {Pb?*] in PbCl, solution, M Kop average Ke, solubility of PoCl,, in gper 100 mL chemistry handbook value for solubility at 20°, g per 100 mL name rated solution. determination 1? 2 3 20.2 20.4 20.1 25.00 22.00 20.10 0.2543 0.2276 0,2051 section ” date