Determination of Solubility Product

Determination of Solubility Product

Jay Patel & Dishant Patel

Chemistry Department, College of Humanities and Sciences, De La Salle Health Sciences Institute, Dasmarinas Cavite

Date Performed: 03/01/16

Date Submitted:  05/19/16

ABSTRACT

______________________________________________________________________________

The main objective of this experiment was to determine the solubility product constant of Ba(IO3)2 and measure the absorbance of the equilibrium mixture. This experiment also aims to investigate the factors that influence the changes in the Ksp of an partially soluble ionic compound. The precipitate of Ba(IO3)2 was produced from 0.0200 M Ba(NO3)2 and 0.0350 M KIO3. This was then dissolved unitl saturation in different media including deionized water, Ba(NO3)2, and media of varying concentrations of KI which was all titrated with 1 M HCl. The data was then computed to yield concentrations for [IO3- ] and [Ba2+], where the latter is also the solubility of the compound. Further calculations gave values for the solutions ionic strengths and each sets solubility product constant. When the data of the KI media were plotted, it showed that the solutions decreased in solubility through increasing ionic strength. Solubility also decreased when Ba(IO3)2 was dissolved in Ba(NO3)2.The experiment was a failure in the common-ion effect part, but was successful in the diverse-ion effect. This experiment can be improved by accuracy in the saturated solution preparation as well as in titration techniques.

______________________________________________________________________________

INTRODUCTION

In this experiment, the Ksp of barium iodate was determined from the reaction of barium nitrate with potassium iodate. Equilibrium was established from the precipitate formed. The solubility product constant of a compound is the product of the molar concentrations of the constituents ions, each raised to the power of its stoichiometric coefficient in the equilibrium equation. The value of Ksp indicates the solubility of an ionic compounds. The smaller the value the less soluble the compound is in water.

In general, the solubility product constant, Ksp, is the equilibrium constant for the solubility equilibrium of a slightly soluble (or nearly insoluble) ionic compound. It equals the product of the equilibrium concentrations of the ions in the compound, each concentration raised to a power equal to the number of such ions in the formula of the compound.

Ba(NO3)2 (aq) + KIO3 (aq) → Ba(IO3)2 (s) + KNO3 (aq)

Ba(IO3)2 (s)  ⇌  Ba2+  +  2IO3-  (aq)

Ksp = [Ba2+] [IO3-]

The solubility behavior of Ba(IO3)2 in various mixtures of Ba(NO3)2 and KIO3 was observed. The concentration of iodate ion was determined by spectrophotometric method. The iodate ion was reduced to I2 in acidic medium. The reaction will produce a colred solution which was analyzed by obtaining the absorbance of the resulting solution and relating it to concentration. The reaction is summarized below.

IO3- (aq) + 5I- (aq) + 6H+ (aq) → 3I2 (aq) + 3H2O (l)  

OBJECTIVES

Determine the solubility product constant of Ba(IO3)2 and measure the absorbance of the equilibrium mixture.

METHODOLOGY

A)  Reaction Mixture Preparations

[1] First measure about thirty-five milliliters of twenty millimolar Ba(NO3)2 and transfer to fifty                                                                                                          milliliter dry beaker and measure twenty milliliters of thirty-five millimolar KIO3 and transfer it to fifty milliliter dry beaker. Prepare five test tube and label it.

[2] Piper one milliliter of thirty-five molar KIO3 and transfer it to test tube one. Then pipet two milliliter, three milliliter, four milliliter and five milliliter respectively. Using five milliliter pipet, add five milliliter of twenty molar Ba(NO3)2 to each test tube. Then do for other as required.

[3] By using stirring rod, stir each solution thirty seconds, up and down. Make an observation to each test tube. Put a rubber stopper to test tube that forms a precipitate and slowly invert the test tube twenty times to ensure through mixing and help to bring equilibrium.

[4] For those test tube which did not form any precipate, repeat the stirring process, using stirring rod until the solution get the cloudiness form. Let the test tube stand for ten minutes to let the precipitate to settle out completely.

B) Preparation of Equilibrium Mixture for Analysis

[1] Now Clamp test tube one on iron stand so that you can work on it without being able to move. Make sure not to disturb the precipitate at the bottom of test tube. Using five milliliters pipet, carefully obtain five milliliters of the clear filtrate and transfer to another clean test tube.