Integrated Concepts in Equilibrium

INTEGRATED CONCEPTS IN EQUILIBRIUM

J.F. SO

DEPARTMENT OF MINING, METALLURGICAL, AND MATERIALS ENGINEERING, COLLEGE OF ENGINEERING

UNIVERSITY OF THE PHILIPPINES, DILIMAN, QUEZON CITY, PHILIPPINES

DATE PERFORMED:

INSTRUCTOR’S NAME: SIR JADE NAZARENO

ABSTRACT

The objective of the experiment is to determine the solubility product constant, Ksp, of Ca(OH)2

through titration of a saturated solution of Ca(OH)2. The experiment also aims to distinguish and

investigate the factors that influence the changes in the Ksp of a partially soluble ionic compound. Solid

Ca(OH)2 was added to 60mL of three different media. The resulting supernatant was then filtered and

25-mL of the aliquot was titrated by 0.1M HCl. Obtained data was then used to calculate for the

concentrations of OH- and Ca2+, wherein the value of the latter also served as the molar solubility of the

compound. Some more calculations were made to determine the experimental Ksp and ionic strength

“μ” of some of the solutions used. When the data was compared, the decreased Ksp of the Ca(OH)2 –

CaCl2 mixture confirmed the effect of the diverse-ion. Further improvements on the experiment could

be made through the use of a new indicator as well as proper preparation of solutions and better

titration techniques.

INTRODUCTION

When sparingly soluble ionic solids are

placed in water, an equilibrium reaction,

where AxBy is a hypothetical solid, takes place

in the form of:

AxBy(s) ⇌ xAy+ (aq) + yBx- (aq) (1)

The equilibrium constant, Keq, for this

reaction is referred to as the solubility

product constant, Ksp, of the ionic solid. [1]

Because of this relationship, Ksp is calculated

similarly to that of Keq:

Keq = Ksp = [Ay+]x [Bx-]y (2)

In the experiment, the solubility product

constant, Ksp, of Ca(OH)2 was obtained

through titration. The equilibrium reaction of

Ca(OH)2 is expressed as:

Ca(OH)2(s) ⇌ Ca2+ + 2OH- (3)

From the chemical equation above, the Ksp of

Ca(OH)2 can be expressed as:

Ksp...