1. The ester interchange method is more favoured than direct phosgenation of bisphenol A for the production of polycarbonates. State true or false.
a) true
b) false
Explanation: Direct phosgenation reaction is better done in the presence of solvents and even diluted with certain other solvents. Thus, the ester interchange method is more favoured as it allows avoidance of handling of toxic and inflammable solvents and thus allowing avoidance of costs of solvents and solvent recovery.
2. Which of the following monomer pairs polymerize to give epoxy resin?
a) epichlorohydrin and bisphenol A
b) bisphenol A and diphenyl carbonate
c) bisphenol A and phosgene
d) none of the mentioned
Explanation: The polycondensation reaction between epichlorohydrin and bisphenol A gives epoxy resin as the product. The other two monomer pairs react and polymerize to give polycarbonates.
3. What is the use of epoxy resin from commercial point of view?
a) as strength adhesives
b) as cementing agents
c) cast objects and laminates
d) all of the mentioned
Explanation: The epoxy resins are especially used as high strength adhesives, cementing agents in building industry and also in glass fibre reinforced cast objects and laminates.
4. What is the common name of the polymer poly (ethylene terephthalate)?
a) dacron
b) technora
c) viton
d) nomex
Explanation: Poly (ethylene terephthalate) is commonly known as Dacron or Terylene.
5. What is the common or brand name of the polymer polyacrylonitrile?
a) mylar
b) orlon
c) technora
d) ultem
Explanation:The common brand name of poly acrylonitrile (PAN) is Orlon.
6. Which tree gives out the latex to obtain natural rubber?
a) eucalyptus
b) hevea brasiliensis
c) anogeissus
d) astragalus
Explanation: Hevea tree produces a milk-white latex that contains the natural rubber hydrocarbon present in the form of fine emulsion in an aqueous serum which is then later processed to give natural rubber.
7. Which substance is added to the dilute latex to prevent darkening of latex?
a) sodium bisulfite
b) potassium sulfite
c) sodium sulfate
d) potassium sulfate
Explanation: A little amount of sodium bisulfite is added to the dilute latex before tapping to prevent darkening or discoloration of the latex which may otherwise develop as a consequence of an enzymatic reaction in the latex involving its phenolic constituents producing the dark coloured pigment melanin.
8. Which component has the maximum composition in the Hevea rubber latex?
a) rubber hydrocarbon
b) water
c) proteins
d) sugars
Explanation: Hevea latex consist of 55-65 % of water, 30-40% of rubber hydrocarbon while proteins and sugars are present in little amount.
9. Which of the following represents natural rubber chemically?
a) cis 1,4-polyisoprene
b) trans 1,4-polyisoprene
c) cis 1,3-polyisoprene
d) trans 1,3-polyisoprene
Explanation:Natural rubber is chemically known by cis 1,4-polyisoprene. This structure of natural rubber was confirmed by identifying the products derived from its ozonolysis.
10. What are the sequential processes through which rubber latex undergo to give natural rubber?
a) tapping-preservation-coagulation
b) preservation-tapping-coagulation
c) tapping-coagulation-preservation
d) coagulation-tapping-preservation
Explanation:The rubber latex from hevea tree firstly undergoes tapping, then it is preserved using a preservative like sodium pentachlorophenate followed by coagulation using acetic acid o formic acid.