Determining The Classification Of Six Known Chemicals

I. INTRODUCTION
This report discusses an experiment, the objective of which was to determine the classification of six known chemicals: sodium nitrate, barium chloride, silicon carbide, naphthalene, urea, and antimony and two unknown chemicals XIa and XIb. Since each type of chemical (ionic, molecular, macromolecular and metallic) has its own set of properties, by testing these properties and finding them out for each chemical, it was possible to classify them. The properties tested during this experiment were solubility in water, toluene, and ethanol and the electrical resistance for those soluble in water. The melting point was tested for the two unknown chemicals.

II. MATERIALS AND PROCEDURES

List of chemicals used: Sodium nitrate,

3) Distilled water was added to dissolve it.
4) The two electrodes were placed in the water while making sure that they were immersed in the solution but not touching each other or the surface of the beaker.
5) After about 10 seconds, the average of the readings were taken and recorded.

III. RESULTS

Substance Approx. Melting Point Solubility
Water Non Polar Polar Electrical Resistance in Ohms Classification
Sodium Nitrate Sol. Insol sol N Ionic
Barium Chloride Sol. Insol. sol N Ionic
Silicon Carbide Insol. Insol. Insol Macromolecular
Napthalene Insol. Sol. Sol Molecular
Urea Sol. Sol. Insol N Molecular
Antimony Insol. Insol. Insol N Metallic
XIa Not melted at 150°C Sol. Insol sol Ionic
XIb Not melted at 150°C Insol. Insol. Insol Metallic

IV.

It melts at 750°C without decomposing, and the melt conducts an electric current. It dissolves readily in water, to produce an electrically conductive solution. What would be the classification of a substance, based on this information?
Ans: Ionic. As mentioned in answer to question to 2b, ionic compounds have free mobile ions for conduction of electricity only in the molten state and in aqueous state. Hence, given substance is most likely to be ionic as it exhibits conductance only in these states. In addition to that, it has high melting point, which is characteristic of ionic compounds. [6]

4) A lustrous grey – white solid melts at 1650°C. It is electrically conductive as both a solid and a liquid, but not soluble in either water or any organic solvent. Classify the substance as best you can from these properties.
Ans: Metallic. The high melting point rules out the molecular category due to the fact that molecular compounds have low melting point. [7] Conductivity in solid state leaves no doubt to the fact the substance is not ionic. And since it is lustrous, it must be metallic. (The reason why has been mentioned in the previous