All questions of The p-Block Elements (Group 13 & 14) for NEET Exam

Extraction of Aluminium from Alumina (Al2O3)

Aluminium is an important metal that is widely used in various industries due to its low density, high strength, and excellent corrosion resistance. It is extracted from its ore, alumina (Al2O3), through a process called electrolysis. The correct combination of molten mixture for the extraction of aluminium by electrolysis is given in option 'C', which consists of Al2O3, Na3AlF6, and CaF2.

Electrolysis of Alumina (Al2O3)

The extraction of aluminium from alumina involves the process of electrolysis. In this process, a molten mixture of alumina, Na3AlF6, and CaF2 is used as an electrolyte. The following steps explain the extraction process in detail:

1. Formation of Cryolite (Na3AlF6):
- Cryolite is a mineral that is added to the mixture to lower the melting point of alumina and improve its conductivity.
- Na3AlF6 is formed by the reaction between alumina and sodium fluoride (NaF).
- 2 Al2O3 + 6 NaF → 2 Na3AlF6 + 3 O2

2. Electrolysis of Alumina (Al2O3):
- The mixture of alumina, Na3AlF6, and CaF2 is heated to a high temperature to form a molten electrolyte.
- The mixture is then placed in an electrolytic cell, which consists of a carbon anode and a carbon cathode.
- The carbon anode is connected to the positive terminal of a power supply, while the carbon cathode is connected to the negative terminal.
- The molten mixture acts as the electrolyte, and alumina is dissolved in it.
- When an electric current is passed through the electrolyte, the following reactions occur:
- At the anode (oxidation): 2 O2- → O2 + 4 e-
- At the cathode (reduction): 4 Al3+ + 12 e- → 4 Al
- The oxygen ions (O2-) are attracted to the anode and combine to form oxygen gas (O2), which is released.
- The aluminium ions (Al3+) are attracted to the cathode and gain electrons to form aluminium metal (Al), which is deposited on the cathode.

Advantages of the Molten Mixture

The molten mixture of alumina, Na3AlF6, and CaF2 has several advantages for the extraction of aluminium:
- Lower Melting Point: The addition of cryolite (Na3AlF6) lowers the melting point of alumina, reducing the amount of energy required for the process.
- Improved Conductivity: The presence of the molten mixture enhances the conductivity of the electrolyte, allowing for efficient electrolysis.
- Electrolyte Stability: The molten mixture remains stable at high temperatures, ensuring the continuous flow of current and the extraction of aluminium.

Conclusion
The correct combination of the molten mixture for the extraction of aluminium from alumina (Al2O3) is option 'C', which consists of Al2O3, Na3AlF6, and CaF

The type of structure where one oxygen atom of [SiO4]4- is shared with another tetrahedron is called a sheet structure or a layered structure.

Correct answer is sodium bro

Hydrolysis of (CH3)2SiCl2 followed by condensation polymerisation is the correct process for the formation of a straight chain polymer.

Explanation:
Hydrolysis is a chemical reaction in which a compound reacts with water to form new compounds. In this case, (CH3)2SiCl2 undergoes hydrolysis to form (CH3)2Si(OH)2, also known as dimethylsilanediol.

Condensation polymerisation is a process in which monomers join together to form a polymer with the elimination of a small molecule such as water. In this case, the dimethylsilanediol monomers undergo condensation polymerisation to form a straight chain polymer.

Here is a detailed explanation of each step:

1. Hydrolysis of (CH3)2SiCl2:
(CH3)2SiCl2 + 2H2O → (CH3)2Si(OH)2 + 2HCl
In this step, (CH3)2SiCl2 reacts with water to form (CH3)2Si(OH)2 and hydrochloric acid (HCl) as a byproduct.

2. Condensation polymerisation:
(CH3)2Si(OH)2 + (CH3)2Si(OH)2 → -[(CH3)2Si-O-Si(CH3)2]- + 2H2O
In this step, the dimethylsilanediol monomers, (CH3)2Si(OH)2, react with each other to form a straight chain polymer, -[(CH3)2Si-O-Si(CH3)2]-, also known as polydimethylsiloxane (PDMS) or silicone. This reaction involves the elimination of water molecules.

The resulting polymer, polydimethylsiloxane (PDMS), is a straight chain polymer with repeating units of (-Si-O-)n, where n represents the number of repeating units. PDMS is commonly used in various applications, including lubricants, adhesives, sealants, and coatings, due to its unique properties such as high thermal stability, low surface tension, and excellent electrical insulation.

In conclusion, the correct process for the formation of a straight chain polymer is the hydrolysis of (CH3)2SiCl2 followed by condensation polymerisation. This process results in the formation of polydimethylsiloxane (PDMS) or silicone.