Experiment 3 - Percent Composition

Objective - Determine the percentage of oxygen in potassium chlorate (KClO₃).

Introduction

The decomposition of potassium chlorate (at temperatures above 400^oC) is described by the equation:

A weighed sample of potassium chlorate will be heated until all the oxygen is released. The relative amounts of oxygen and potassium chloride (KCl) will be measured by determining the amount of residue (KCl) which remains after heating. The decrease in weight after heating will represent the amount of oxygen originally present in the sample.

To test that the residue is potassium chloride it will be dissolved in water, acidified and then tested with silver nitrate (AgNO₃) solution. If the residue is potassium chloride then the acidified solution will react with the silver nitrate solution producing silver chloride (AgCl), which will appear as a white precipitate.