Ksp Of Magnesium Oxalate

The Ksp of Magnesium Oxalate

Abstract

The Ksp for the acid catalyzed titration of the saturated oxalate is 1.8 x 10-3.

Introduction

In this experiment, the solubility equilibrium for the salt magnesium oxalate must be found in order to determine a solubility product constant. Solubility equilibrium is a type of dynamic equilibrium which exists when a chemical compound in the solid state is in chemical equilibrium with a solution of that compound. At the point of equilibrium the solution becomes saturated. The chemical reaction used to find this constant is as follows: MgC2O4 (s) ↔Mg(aq)2++ C2O4 (aq)2- Kc= Mg2+[C2O42-][MgC2O4] Ksp=Mg2+[C2O42-]
The solid salt magnesium oxalate is prepared through the following precipitation reaction: Mg(SO4)(aq)+NaC2O4 (aq) → MgC2O4 (s)+NaSO4 (aq)
Next, the concentration of the Mg2+ and C2O42- ions is found through a redox titration. This redox titration uses a standardized potassium permanganate solution. The potassium permanganate solution is standardized by titrating it with samples of iron(II)ammonium sulfate hexahydrate . The end point is reached when the solution has turned light purple which is a result of excess amounts of MNO4-. This reaction can be summed up using the following formula:
5Fe2++8H++MnO4- →5Fe3++Mn2++4H2O
After standardization, the potassium permanganate solution is then titrated with 3 different magnesium oxalate solutions. To find the concentration of the C2O42- the balanced net ionic redox reaction formula is used:
5C2O42-+16H++2MnO4- →10CO2+2Mn2++8H2O
It is important to note the addition of sulfuric acid (9M H2SO4) in performing this experiment because of the following reasons: 1) Sulfuric acid keeps the iron (II) from air oxidizing into iron (III) 2) Sulfuric acid keeps the iron (II) from hydrolyzing into Fe(OH)2 3) Sulfuric