Practice Macromolecules MCQs for BDS Dental Entry Test Chemistry — topic-wise sets with solved answers.
Q1. A chemist synthesizes a polymer using only vinyl chloride as the starting material. What classification describes this resulting macromolecule based on monomer type?
Answer: Homopolymer
Explanation: Homopolymers consist of a single type of monomer; copolymers, the most tempting distractor, require at least two different monomer types.
Q2. During the industrial production of Nylon 6,6, adipic acid reacts with a specific diamine. Identify the exact number of carbon atoms in this diamine.
Answer: Six
Explanation: Nylon 6,6 is named for the six carbons in both adipic acid and hexamethylenediamine; Nylon 6 is a common distractor.
Q3. A manufacturer requires a polymer for electrical insulation that is resistant to chemicals and non-inflammable. Which vinyl polymer is most suitable?
Answer: Polyvinyl chloride
Explanation: PVC is uniquely non-inflammable due to its chlorine content; polyethylene is a tempting distractor but lacks this specific chemical resistance.
Q4. In polymer chemistry, the length of a polymer chain is often expressed by a specific ratio. What is the term for the number of repeating units?
Answer: Degree of polymerization
Explanation: Degree of polymerization represents the total number of monomer units; molar mass factor is tempting but refers to the total weight.
Q5. A technician heats a mixture of phenol and formaldehyde in the presence of an acid catalyst to form a hard, infusible resin. What type of polymerization is occurring?
Answer: Condensation polymerization
Explanation: Bakelite forms via condensation with water loss; addition polymerization is tempting but involves no byproduct and occurs mostly in vinyl monomers.
Q6. Terylene is a widely used synthetic fiber in the textile industry. Which two functional groups react to form this specific polyester?
Answer: Alcohol and Carboxylic acid
Explanation: Polyesters form between diols and dicarboxylic acids; amines and acids form polyamides like Nylon, which is a very common distractor.
Q7. A plastic material softens upon heating and regains its hardness on cooling without undergoing any chemical change. How is this polymer classified?
Answer: Thermoplastic polymer
Explanation: Thermoplastics soften repeatedly with heat; thermosetting polymers are tempting but they harden permanently due to cross-linking when heated the first time.
Q8. Natural rubber is a polymer of isoprene. According to IUPAC nomenclature, what is the correct chemical name for this specific monomer?
Answer: 2-Methyl-1,3-butadiene
Explanation: Isoprene is 2-methyl-1,3-butadiene; 2-chloro-1,3-butadiene is the monomer for neoprene, which is a common synthetic rubber distractor.
Q9. During the free-radical polymerization of ethene, an organic peroxide is added to the reaction mixture. What is the specific role of this peroxide?
Answer: Polymerization initiator
Explanation: Peroxides generate free radicals to start the reaction; inhibitors are tempting but they actually stop or slow the polymerization process.
Q10. A student examines the linkage between two amino acids in a polypeptide. Which atoms directly form the peptide backbone connection?
Answer: Carbon and Nitrogen
Explanation: The peptide bond is a C-N linkage; C-O is tempting but refers to the carbonyl bond within the amide group.
Q11. A sample of egg white coagulates when heated to 100 degrees Celsius. Which structural level of the protein remains intact during this denaturation?
Answer: Primary structure
Explanation: Denaturation disrupts folding but leaves the amino acid sequence untouched; secondary structure is tempting but it unfolds during the process.
Q12. Starch consists of two polysaccharides, one of which is water-soluble and forms a blue color with iodine. Identify this component.
Answer: Amylose
Explanation: Amylose is the unbranched, water-soluble fraction; amylopectin is tempting but is branched and generally insoluble in cold water.
Q13. A lab analyst adds a drop of iodine solution to an unknown carbohydrate sample, resulting in a deep red color. Which substance is likely present?
Answer: Glycogen
Explanation: Glycogen gives a red color with iodine; starch is a tempting distractor but yields a characteristic deep blue color.
Q14. The quality of an edible oil is tested by determining the milligrams of KOH required to neutralize the fatty acids in one gram of oil. What is this value?
Answer: Acid value
Explanation: Acid value measures free fatty acids; saponification value is tempting but measures both free and combined fatty acids in the sample.
Q15. To determine the degree of unsaturation in a sample of vegetable ghee, a chemist uses a halogen titration. Which parameter is being measured?
Answer: Iodine value
Explanation: Iodine value quantifies C=C double bonds; saponification value is tempting but relates to molecular weight and total ester content.
Q16. Epoxy resins are used as high-strength adhesives. Which substance is commonly reacted with epichlorohydrin to produce these industrial resins?
Answer: Bisphenol-A
Explanation: Bisphenol-A reacts with epichlorohydrin for epoxy synthesis; phenol is tempting but is used primarily for Bakelite production.
Q17. At a specific pH known as the isoelectric point, an amino acid exists as a zwitterion. Which functional groups carry the charges in this state?
Answer: COO- and NH3+
Explanation: The carboxyl group loses a proton and the amino group gains one; COO+ is chemically impossible and a common distractor.
Q18. The alpha-helix structure of a protein is maintained by intramolecular forces. Between which specific groups do these bonds form?
Answer: N-H and C=O groups of the backbone
Explanation: Alpha-helices are stabilized by backbone H-bonds; side chain interactions are tempting but stabilize the tertiary structure instead.
Q19. High-density polyethylene (HDPE) is produced under specific conditions to ensure a linear structure. Which catalyst is essential for this process?
Answer: Ziegler-Natta catalyst
Explanation: Ziegler-Natta catalysts produce linear HDPE; peroxides are tempting but produce branched low-density polyethylene (LDPE) via free radical mechanism.
Q20. Cellulose is a major structural component of plant cell walls. Which specific glycosidic linkage connects the glucose units in its chain?
Answer: Beta-1,4-linkage
Explanation: Cellulose features beta-1,4-linkages; alpha-1,4-linkage is tempting but is the characteristic bond found in starch (amylose).
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