Rubber and vulcanisation

36 questions on Rubber and vulcanisation from the Polymers chapter: 8 NEET level, 14 JEE Main, 14 JEE Advanced. Each one opens with its answer and solution.

• The monomer of natural rubber is NEET level
• Vulcanisation of natural rubber is carried out by heating it with NEET level
• Neoprene is a polymer of NEET level
• Buna-S is a copolymer of NEET level
• Natural rubber and gutta-percha are both polymers of isoprene. They differ in that JEE Main level
• Buna-N is prepared from JEE Main level
• All of the following are consequences of vulcanising natural rubber with a few percent of sulfur EXCEPT JEE Main level
• In vulcanisation of polyisoprene, sulfur cross-links are believed to attach mainly at JEE Main level
• Assertion (A): Raw natural rubber is soft and sticky and becomes brittle in cold weather. Reason (R): Its linear cis-polyisoprene chains are held only by weak v... JEE Main level
• The repeat unit of neoprene is -[CH2-C(Cl)=CH-CH2]- (C4H5Cl; C 12, H 1, Cl 35.5). A neoprene sample has molar mass 44250 g mol^-1. Its degree of polymerisation ... JEE Main level
• Buna-S is made by 1,4-addition of buta-1,3-diene together with styrene, C6H5-CH=CH2. How many non-aromatic C=C bonds are there in a segment of the copolymer mad... JEE Main level
• Which of the following statements about the vulcanisation of natural rubber are correct? JEE Advanced level
• Which of the following statements about natural rubber and gutta-percha are correct? JEE Advanced level
• Neoprene is made by 1,4-addition polymerisation of 2-chlorobuta-1,3-diene, giving the repeat unit -[CH2-C(Cl)=CH-CH2]- (C4H5Cl, C 12, H 1, Cl 35.5). Which state... JEE Advanced level
• A rubber sample has three groups of chains: 250 chains of molar mass 26000 g mol^-1, 450 chains of 58000 g mol^-1 and 300 chains of 97000 g mol^-1. Using overli... JEE Advanced level
• A sample of 680 g of polyisoprene (repeat unit C5H8, 68 g/mol) is vulcanised so that there is one -S-S- bridge (two sulfur atoms, S = 32) for every 100 isoprene... JEE Advanced level
• A Buna-S chain has three butadiene units (C4H6, 54 g/mol each in the chain) for every one styrene unit (C8H8, 104 g/mol in the chain). Neglecting end groups, th... JEE Advanced level
• Natural rubber (repeat unit C5H8, 68 g/mol, one C=C per unit) adds bromine across its double bonds, C=C + Br2 -> CBr-CBr. In a vulcanised sample, 4 percent of t... JEE Advanced level
• Which of the following statements is/are correct? (One or more options may be correct.) JEE Advanced level
• Buna-S can be classified as JEE Main level
• Which statement comparing natural rubber and gutta-percha is correct? JEE Main level
• Which of the following effects result from vulcanising natural rubber with about 3-5 percent sulfur? (One or more options may be correct.) JEE Advanced level
• Match the rubber in Column I with the monomer(s) in Column II. Column I: (P) Buna-S, (Q) Buna-N, (R) neoprene, (S) natural rubber. Column II: (1) 2-chlorobuta-1... JEE Advanced level
• Buna-S is a copolymer of NEET level
• Ozonolysis of natural rubber followed by reductive work-up (Zn/H2O) cleaves every C=C of the 1,4-polyisoprene chain. The main product is JEE Advanced level
• Natural rubber is vulcanised by heating it with NEET level
• The mass percentage of chlorine in neoprene (repeat unit -[CH2-C(Cl)=CH-CH2]-, C 12, H 1, Cl 35.5) is closest to JEE Main level
• The monomer unit of natural rubber is NEET level
• Which of the following statements about natural rubber and gutta-percha is/are correct? (One or more options may be correct.) JEE Advanced level
• Complete catalytic hydrogenation of natural rubber saturates every C=C. The molar mass of the saturated repeat unit (C 12, H 1) is JEE Main level
• A 100 g sample of natural rubber (repeat unit C5H8, 68 g/mol) is vulcanised with 3.2 g of sulfur (S = 32). Assume all the sulfur is present as single S atoms, e... JEE Main level
• Buna-S contains styrene and buta-1,3-diene units in the mole ratio 1 : 3 (end groups ignored; C 12, H 1). The mass percentage of carbon in the copolymer is JEE Advanced level
• During vulcanisation, sulfur cross-links form chiefly at JEE Main level
• A 8.0 g sample of rubber compound is 85 percent natural rubber (cis-polyisoprene, C5H8 units of 68 g/mol) by mass; the rest does not react with bromine. Assumin... JEE Advanced level
• Which one of the following rubbers contains nitrogen? JEE Main level
• Neoprene is a polymer of NEET level