Question

Give reason for the following: (a) Carbon does not form complex compounds. (b) \(\mathrm{Pb}_{3} \mathrm{O}_{4}\) is a mixed oxide. (c) \(\mathrm{CO}_{2}\) is a gas while silica is a solid. (d) \(\mathrm{CCl}_{4}\) can not be hydrolysed in water. (e) \(\mathrm{SnO}_{2}\) is amphoteric.

Short answer

Carbon does form complex compounds due to catenation. \(\mathrm{Pb}_{3} \mathrm{O}_{4}\) is a mixed oxide as it contains \(\mathrm{Pb}\) in two different oxidation states. \(\mathrm{CO}_{2}\) is a gas while silica is a solid due to their different molecular structures. \(\mathrm{CCl}_{4}\) can't be hydrolysed in water as carbon in \(\mathrm{CCl}_{4}\) is surrounded by chlorine atoms. \(\mathrm{SnO}_{2}\) is amphoteric as it reacts with both acids and bases.

Step-by-step solution

Answer (a)

Carbon can actually form complex compounds. This particular attribute of carbon is known as catenation. Carbon can form long chains, branched chains and rings by binding with its own atoms, producing millions of compounds.

Answer (b)

\(\mathrm{Pb}_{3} \mathrm{O}_{4}\) is a mixed oxide because it contains lead in two different oxidation states. It's actually a combination of two lead oxides - \(\mathrm{PbO}\) and \(\mathrm{PbO}_{2}\). Therefore, it is called a mixed oxide.

Answer (c)

\(\mathrm{CO}_{2}\) is a gas while silica is a solid because of their different molecular structures. Carbon dioxide is a simple covalent molecule with weak van der Waals forces between the molecules, which easily overcome, thus it is a gas. On the other hand, silica, or silicon dioxide, has a giant covalent structure with strong covalent bonds between atoms throughout the structure, which makes it a solid.

Answer (d)

\(\mathrm{CCl}_{4}\) does not get hydrolysed in water because carbon in the \(\mathrm{CCl}_{4}\) molecule is surrounded by 4 chlorine atoms, making it impossible for water molecules to attack the carbon atom.

Answer (e)

\(\mathrm{SnO}_{2}\) is amphoteric because it can behave as both an acid and a base. This means, \(\mathrm{SnO}_{2}\) can react with both acids and bases to form salts and water, which is characteristic of an amphoteric oxide.

Key concepts

Catenation

Catenation is the ability of an element to form bonds with other atoms of the same element. This property is exemplary in carbon, making it one of the most versatile elements in forming a vast array of compounds.

Due to catenation, carbon can form:

• Long chains of atoms, such as in hydrocarbons.
• Branched chains, adding complexity and variety to molecules.
• Rings, which are crucial in the structure of many organic compounds.

These unique formations are possible because carbon atoms have the ability to form stable covalent bonds with each other. This versatility allows carbon to create millions of complex structures, making it a cornerstone of organic chemistry.

Mixed Oxides

Mixed oxides are compounds containing more than one type of oxide within the same structure. An excellent example is \(\mathrm{Pb}_{3} \mathrm{O}_{4}\), which is a mixed oxide because it involves lead being in two different oxidation states.

Specifically, \(\mathrm{Pb}_{3} \mathrm{O}_{4}\) is a mixture of:

• \(\mathrm{PbO}\)
• \(\mathrm{PbO}_{2}\)

This composition makes it unique and gives it distinct chemical properties. The presence of multiple oxidation states within a mixed oxide can mean different chemical reactivities and applications, such as in pigments and as oxidation catalysts.

Molecular Structures

Molecular structures dictate the physical states and properties of substances. For instance, carbon dioxide (\(\mathrm{CO}_{2}\)) and silica provide a fascinating contrast due to their differing molecular structures.

For \(\mathrm{CO}_{2}\):

• It is a simple covalent molecule.
• With weak van der Waals forces between the molecules.
• These forces are easily overcome, making \(\mathrm{CO}_{2}\) a gas at room temperature.

In contrast, silicon dioxide (silica):

• Has a giant covalent structure.
• Possesses strong covalent bonds throughout its structure.
• These strong bonds render silica solid at room temperature.

The strength and type of bonding significantly influence whether a substance exists as a gas, liquid, or solid under given conditions.

Hydrolysis

Hydrolysis is a process where a chemical compound reacts with water, leading to its breakdown. However, certain molecules resist hydrolysis due to their structure.

A prime example is carbon tetrachloride (\(\mathrm{CCl}_{4}\)). In \(\mathrm{CCl}_{4}\):

• The carbon atom is completely surrounded by four chlorine atoms.
• This structural arrangement prevents water molecules from accessing the carbon atom.
• As a result, \(\mathrm{CCl}_{4}\) is non-hydrolyzable.

Understanding the spatial arrangement of atoms in a molecule allows chemists to predict whether a compound will undergo hydrolysis, impacting its reactivity and applications.

Amphoteric Oxides

Amphoteric oxides are unique compounds that react both with acids and bases. This dual reactivity makes them versatile in chemical reactions.

Take tin(IV) oxide (\(\mathrm{SnO}_{2}\)) as an example. It can:

• React with acids to form salts and water.
• Also react with bases to produce similar products.

This characteristic means \(\mathrm{SnO}_{2}\) is amphoteric. This property is particularly significant in industrial processes where flexibility in reacting conditions is desired. Recognizing and utilizing amphoteric behavior is essential in developing efficient chemical processes.