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Experiment 17A. A Solubility Product Constant Procedure Getting Started 1. Obtain a 10 ml pipet, a 50 mL buret, and 2 pieces of 120 cm filter paper Preparing Saturated Solutions of M10J MIO), is an insoluble divalent iodate salt. The identity of the cation M-is unknown. 1 Prepare MIO,), by adding S0 ml of o.2 M KIO, to 20 mL of 1 Molar M(NO,J, in a 150 mt 2. Stir the mixture vigorously with a stirring rod. A white, crystalline precipitate of M(IO,) beaker. is expected Let the mixture stand for a few minutes while you prepare for gravity filtration. Filter the precipitate. Rinse the remnants from the beaker onto the filter paper, using distilled water from a plastic wash bottle. 3. 4. 5. Was 6. Place about 1/ h the precipitate on the filter paper with two small portions of distilled water all 2 of the wet precipitate onto a clean labeled 150 mL beaker, using a sm spatula. Save the remaining portion of the precipitate on the filter paper to use if needed. . Use a graduated cylinder to add 80 mL of distilled water to the 150 mL beaker containing the precipitate. 8. Stir the solution thoroughly using s stirring rod. 9. Allow the stirring rod to remain in its beaker, and let the mixture stand for at least 5 minutes with occasional stirring. Note that this will be a saturated solution, meaning you will see some solid in equilibrium with a saturated solution. Analyzing the Saturated Solutions of M(IO), Doing the Trial Titration The goal of this part of the experiment is to determine the molarity of the ions in the saturated solution. Extraneous water must not be introduced during the filtration and sampling or the molarity of the ions will be modified. 1. Filter the mixture obtained in the first part of the experiment through a piece of new dry filter paper and a dry filter funnel. Catch the filtrate in clean, dry labeled beaker. Do not wash the precipitate on the filter paper. Rinse a 10 mL pipet with distilled water and shake out as much water as you can. Rinse the pipet with two small portions portions 2. (about 2 ml each) of the filtrate. Discard these 3. Pipet 10.0 mL of the filtrate into a clean 125 mL Erlenmeyer f 4. Add 20 mL distilled water into the flask using a clean graduated cylinder. 5. Dissolve about 1 cm, of solid KI into the solution. Add 20 drops of 2 M HCl to the flask. and swirl to obtain a homogenous solution. 6. Fill the buret with 0.0250 M Na,S,O, solution. 7. Record the initial buret reading to the nearest 0.1 mL. 8. Place the flasks under the buret with the tip inside the mouth of the flask. Place a piece of white paper under the flask. Add 40 drops of a 0.2% starch solution. The solution should turn blue 9. 10. Begin a trial titration by adding increments of about 1 mL of the Na,s,o, solution. Swirl the solution after each addition of the titrant. 11. The trial titration is complete when the addition of about 1 mL causes the solution to Record the buret reading to the nearest 0.1 mL become colorless. Doing the Exact Titration 1. Repeat steps 3 to 9 from the previous section (Trial Titration) 2. Subtract 2 mL from the volume found in the trial titration. Rapidly add the resulting volume to the flask from the buret at once. 3. Continue the titration on a drop by drop basis, swirling the flask after each drop, until one drop causes the complete disappearance of the color. Record the buret reading to the nearest 0.1 mL. 4. Experiment 17A. A Solubility Product Constant Report Student Name Lab Partner Complete the following data Unknown sample # Trial Titration Initial buret reading (ml) Final buret reading (ml) Volume of Na,S,O, (ml) Initial buret reading (ml) 2 y.em Exact Titration 2 ml Final buret reading (m)53. 7m Volume of Na S,O, (ml) Concentration of Na,S,o, (M). O2S 21.6m Calcutate for the exact titration only (show calculations): Moles of Na S,O, 00.0276 Moles of IO, present in your sample Moles = mo les s03 o To ano o.oo1S Molar Concentration of IO, 1 o00m L e Solubility of M(IO,),2 2. . Ksp for M(IO) 2t Q1) Which of these experimental procedures will NOT introduce an error to your determination of Kps? Choose and explain your answer a) The original precipitate obtained in the first part is not washed with water b) The final precipitate of M(IO,)2 is washed with water c) You accidentally add more water than 20 ml on step 4 (titration part) d) The concentration of Na,S,O, was not correctly standardized

Answer 1

The correct option is B, washing the M (IO3) 2 does not affect the calculation of Ksp.

Because the other options are not correct:

A) The precipitate of the first part should not be washed with water.

C) Change the steps by accident, they try an error.

D) Not knowing the correct concentration of titrant, try an error.

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