1. What is mean by catalytic cracking?
Larger molecules of hydrocarbon from heavier fractions can be broken into smaller more valuable molecules. This process is called catalytic cracking. Cracking take place in a huge reactor. In this reactor, particles of catalyst are mixed with the hydrocarbon fraction at a temperature of 500oC. The cracked vapours containing smaller molecules are separated by distillation .
All cracking reactions give two types of product ( 1 ) an alkane with a shorter chain than the original and ( 2 ) a short - chain alkane molecule.
2. How is gasoline obtained from methanol?
Methane is first converted into methanol. The methanol produced is then turned into hydrocarbons using the ZSM - 5 catalyst.
ZSM - 5 is an artificial Zeolite composed of aluminium, silicon and oxygen.
3. State and explain addition Polymerisation ?
Alkanes such as ethane contain a C==C double bond. These molecules can take part in addition reactions where the double bond is broken and other atoms attach to the carbons. The double bond in ethane enables many molecules of ethane to join to each other to form a large molecules, polyethane. This is an addition polymer. High temperature, pressure and catalyst are need for addition polymerisation.
4. How PVC and PTFE prepared?
PVC is poly vinyl chloride. It is formed by the addition polymerisation of chloro ethane or vinyl chloride. It is strong, hard and is used in insulation, pipes and guttering
PTFE is poly tetra fluoro ethane. it is known by the trade name teflon. It was very stable at high temperatures and formed a very slippery surface. It is used for non - stick frying pans, non - stick taps and joints. It is formed by the polymerisation of tetra fluoro ethane .
5. What is polyesters? How is it formed?
Polyesters are condensation co polymers made from two monomers. One monomer has an alcohol group ( -OH) at each end. The other monomer has a carboxylic acid group ( -COOH) at each end. When the monomers react, an ester link is formed with water being lost each time.
6. Differentiate thermoplastic and thermosetting polymers?
Polymers like polythene, poly propane, PVC and polyesters can be softened on heating and melted. They set again when cooked. such plastics are useful because they can be re - moulded. These polymers are known as thermoplastic polymers.
Polymers that can be heated and moulded only once are known as thermosetting polymers.
Example. Melamine. The chain in these polymers are cross - linked to each other. These cross - links in the plastic are permanent chemical bonds. They make the structure rigid when moulded, and no softening takes place on heating.
7. Name three biological polymers? Mention some of its uses in human body?
The biological polymers are
1. Nucleic acids
2.Proteins
3.Carbohydrates
Biological condensation polymers are very important in the human body.
1. Bones are made of minerals embedded in a protein.
2. Fibres in muscles are made of two other proteins.
3.Molecules of DNA that carry genetic information are long - chain nucleic acids.
8. What are proteins?
Proteins are complex compounds that contain carbon, nitrogen, oxygen and sulphur. They fulfill a number of vital functions. Proteins are built from amino acid monomers which contains two functional groups - NH2 and -COOH. Glycine and alanine are two of the simplest amino acids. When they react together, an amide linkage in formed to produce a dipeptide. Chains involving more than 100 amino acids are called proteins.
9. What are enzymes?
Enzymes are protein molecules that catalyse reactions in biological systems. They are very specific catalyst for a certain reaction. Enzymes are unchanged at the end of a reaction and able to repeat the reaction many times over. They are three dimensional structures. High temperatures or extreme pH destroy the structure and the enzymes activity. Thus enzymes are denatured by heat and are sensitive to pH.
10.Give the importance of carbohydrates?
Carbohydrates are important source of energy in our bodies and in all living organisms. A carbohydrate is a compound containing carbon, hydrogen and oxygen only. The ratio of hydrogen to oxygen is 2 : 1.
Examples. Sucrose C12 H22 O11
Glucose C6 H12 O6
All Polysaccharides are long-chain condensation polymers of sugar molecules (monosaccharides) condensation polymerisation of sugar monomers produces carbohydrates such as starch.
