506. What causes the foul smell of the rancid butter?
Butyric acid 

507. Which compound of silver is used in the silvering of mirrors? 
Silver nitrate 

508. What are examples of natural polymers?
Cellulose, starch, rubber, wool & silk 

509. What are the examples of synthetic polymers? 
Polythene, nylon, dacron & Orion

510. The polymers soften on heating and become hard on cooling & can be remoulded, recast and reshaped are known as—– 
Thermoplastics

511. The polymers that can only be moulded into the desired shape on heating once & cannot be reused are known as—— 
Thermosetting plastics 

512. Which is the semi-synthetic polymer obtained by chemical treatment of the wood pulp (cellulose)?
Rayon 

513. What is known as Artificial silk’?
Rayon 

514. What is the type of polymerisation in which simple monomers are united together without loss of small molecules?
Addition polymerisation 

515. Name the important addition of polymers?
Polythene, Teflon, Thermocol, polypropylene, Orion & carbon fibres

516. Which type of polymer is obtained by polymerisation of ethylene?
Polythene (Polyethylene) 

517. Which polymer is used in the insulation wires and manufacturing of squeeze bottles, toys, flexible pipes and buckets?
Polythene 

518. Which type of polymer is obtained by the polymerization of tetrafluoroethylene? 
Teflon

519. Which type of polymer is used as a substitute for wool in making commercial fibres?
Orlon (Acrilon) 

520. Which type of polymer is used in indoor/outdoor carpeting and upholstery? 
Polypropylene

521. Which type of polymers is stronger than steel, stiffer than titanium and lighter than aluminium?
Carbon fibres 

522. Which type of polymer is used in the defence sector as nose tips and head shields of missiles? 
Carbon fibres

523.  What are the examples of condensation polymers?
Bakelite, Glyptal, Nylon 

524.  In which type of polymerisation is simple monomers are joined together with loss of small molecules like water & ammonia?
Condensation polymerisation 

525. What is obtained by the condensation polymerisation of phenol and formaldehyde? 
Bakelite  

526. The natural rubber is a linear polymer of?
Isoprene (2-methyl-l, 3-butadiene) 

527.  The natural rubber is obtained from the —-of the rubber tree? 
Latex

528. Who discovered the synthetic rubber? 
Mathews & Harris

529. What are the examples of the synthetic rubber?
Thiokol, Neoprene, Buna-N & Buna-S 

530.  Which synthetic rubber has a superior re¬sistance to vegetable and mineral oils? 
Neoprene

531. Which synthetic rubber is used for manufacturing conveyor belts, hoses & gaskets?
Neoprene 

532. Which synthetic rubber is resistant to the action of petrol, lubricating oils & organic solvents? 
Buna-N 

533. Which synthetic rubber is used in making oil seals, tank lining etc?
Buna-N 

534. Which synthetic rubber is also known as SBR? 
Buna-S 

535. Which synthetic rubber is used in the manufacturing of automobile tyres & rubber soles? 
Buna-S 

536. Which acid is used for coagulating the latex? 
Formic acid 

537. What should be the percentage of dilution of formic acid before it is added to latex? 
0.5 % 

538. The heating of rubber with sulphur is known as ——? 
Vulcanisation

539. Why rubber is vulcanised? 
To make rubber hard, strong & more elastic 

540. What is the name of the mixture of calcium cyanamide & carbon? 
Nitrolim