Identification of Compounds

Using Physical Properties

Introduction

In this experiment we will use physical properties to identify unknown substances• Solubility of a solid in water, acid, base, organic

solvent• Density of a solid (volume by displacement)• Melting Point

The ExperimentYou and your partner will receive

• 3g of one of the solid compounds on the list to identify by measuring solubility, density and melting point

• An unknown liquid that is on table 2 and you must identify it from its boiling point, density and solubility

Solubility of the Unknown SolidSolubility in:– water– acetone– cyclohexane– isopropanol

• Few crystals in a spot plate well with solvent• Water and isopropanol are polar solvents (dissolve

inorganic salts)• Acetone, and cyclohexane are non-polar and will generally

dissolve organic solids

Melting Point of the Unknown Solid

Melting Point• few crystals capilliary tube • attach rubber band to a thermometer• Immerse the thermometer/capilliary into a water

bath as shown in the figure• begin heating• record the temperature at which the solid starts to

melt

Density of the Unknown Solid

Density• Choose a liquid that your unknown is insoluble in• Place V1=5.0 mL of this liquid in your 10 mL cylinder• Weigh out and add M = 2 g (measure to 4 decimal

places) to the cylinder and record the new volume V2

Solubility of an Unknown Liquid

• You will measure the solubility of an unknown liquid in – acetone– water– cyclohexane– isopropanol

• In four test tubes add 1 mL of your unknown and an equal amount of one of the solvents

• Record your observations

Boiling Point of the Unknown Liquid

• Construct the apparatus below, and record the temperature when small bubbles start to form in the test tube

Density of the Unknown Liquid

• Measure the mass of a small beaker M1

• pipette 10.00 mL of your unknown liquid into the beaker and reweigh it M2