Identifying 3 Unkown Compounds (Physical Properties Of Ionic And Molecular Solids)

Purpose:

• To study some of the physical properties of two types of solids вЂ" ionic and molecular solids.

• To classify three unknown substances as ionic compounds, polar covalent compounds or non-polar covalent compounds.

• To identify the three unknowns.

Observations:

A B C

Solubility in:

• H2O

• 2-Propanol

Soluble

Insoluble

Soluble

Insoluble

Insoluble

Soluble

Conductivity None High None

Melting Point 100 вЂ" 525 в„Ñ" > 525 в„Ñ" < 100 в„Ñ"

Odour Subtle None Very Strong

Concluding Questions:

1. Identify the type of solid in each unkown compound. Support these conclusions with observations.

Compound A is a polar covalent compound because it has many “ in between” properties, such as the following:

• The compound is soluble in water, which is usually an ionic property.

• The compound melted at a temperature between 100 and 525 degrees Celsius, which is not a definite property of ionic or non-polar covalent bonds. Hence, it is covalent.

• Having a subtle odour suggests that that the compound is not intermolecularly strong or weak. The intermolecular formation is moderate, which is a very polar covalent property.

Compound B is an ionic compound for the following reasons:

• It dissolved in water and almost all ionic compounds are very soluble in water.

• It had a very high melting point, which is one of the definite properties of ionic compounds.

• Electrical conductivity was high when dissolved in water, which is a property of all ionic compounds.

Compound C is a non-polar covalent compound for the following reasons

• The compound is insoluble in water but soluble in alcohol.

• The compound does not conduct electricity, which is a definite non-polar property.

• The compound’s smell is very strong, which means that the intermolecular bond is very weak to let the smell pass through. Non-polar covalent compounds have weak intermolecular bonds.

• The compound’s melting point is very low, which is another sign of weak intermolecular structure, a property of non-polar covalent compounds.

2. What does a strong odour indiciate about the ease with which the particles in a solid leave its surface?

A strong odour indicates that the stink of the compound can pass through the intermolecular structure very easily. In other words, a compound having a very strong odour is a sign that the compound’s intermolecular bond is very weak and has molecules far from each other, which cause the smell to pass through. Most compounds that have weak intermolecular bonds are non-polar covalent.

3. From your observations