4: Identification of an Unknown Using Simple Distillation

INTRODUCTION

Physical properties (such as density, solubility, and boiling point) can be used to identify an unknown. For example, we can infer that an unknown liquid with a density of 1.0 g/mL at 25 °C and a boiling point of 100.0 °C at 1 atm is water. However, we would have to run more conclusive tests to either prove or disprove this.

In general chemistry, you learned how to determine the density of an unknown. In this experiment, you will use density and solubility data, along with the boiling point, to identify an unknown organic liquid from a list of known solutions. One technique used to determine the boiling point of an organic liquid is simple distillation. This process involves heating a liquid to its boiling point and then condensing and collecting the resulting distillate. Since only the liquid, and not any impurities present, will collect at the boiling point, simple distillation can also be used to purify an organic liquid.