Solved Exercise, Chem-12, Ch-14


Q.01: Fill in the blanks:

(i) Macromolecules are built up from small units called _______. (monomer)

(ii) Nylon is a polyamide and terylene is a ________. (polyester)

(iii) Nylon is prepared by the reaction of _______ and hexamethylenediamine. (adipic acid)

(iv) Based on their thermal properties, plastics are divided into _________ main classes. (two)

(v) Polyvinyl chloride is a ________ plastic. (thermo)

(vi) Glucose is stored as ________ in the liver. (glycogen)

(vii) Glucose and fructose are water _________ carbohydrates. (soluble)

(viii) Protein after digestion changes to _______. (amino acids)

(ix) Purine and pyrimidine are _________ of nucleic acids. (nitrogenous bases)

(x) Addit ion of a plasticizer _________ the flexibility of the polymer. (increases)

Q.02: Indicate True or False:

(i) Nylon 6,6 and terylene are condensation polymers. (TRUE)

(ii) The disposal of plastics does not cause any pollution problem. (FALSE)

CORRECT: The disposal of plastics causes any pollution problem.

(iii) Fructose is a polysaccharide carbohydrate. (FALSE)

CORRECT: Fructose is a monosaccharide carbohydrate.

(iv) Human beings get no food nutrient from cellulose. (TRUE)

(v) The most abundant and the most important steroid in the human body is vitamin D. (FALSE)

CORRECT: The most abundant and the most important steroid in the human body is cholesterol.

(vi) Enzymes are the compounds containing C, H and O only. (FALSE)

CORRECT: Enzymes are the compounds containing C, H, O and N.

(vii) The degree of unsaturation of fats is measured by their iodine number. (TRUE)

(viii) Activity of an enzyme varies with temperature and pH. (TRUE)

(ix) Nucleic acids are biological catalysts. (FALSE)

CORRECT: Enzymes are biological catalysts.

(x) The nucleic acids are responsible for protein synthesis in the human body. (TRUE)

Q.03: Multiple choice questions.

(i) In which of these processes are small organic molecules made into macromolecules?    

(a)  The cracking of petroleum fractions

(b)  The fractional distillation of crude oil

(c)  The polymerization of ethene

(d)  The hydrolysis of proteins

EXPLANATION: Small ethene molecules polymerize at 100 atm pressure and 400oC temperature to form macromolecule, polythene or polyethylene.

(ii) Which of these polymers is an addition polymer?                             

(a)  Nylon-6,6                                    

(b)  Polystyrene

(c)  Terylene                                     

(d) Epoxy resin

EXPLANATION: Styrene or vinyl benzene undergoes addition polymerization in the presence of catalyst to form polystyrene, a valuable plastic material. Reaction: CH2=CH-C6H5 ¾® —CH2=CH(C6H5)—CH2=CH(C6H5)—

(iii) Which of these is a synthetic polymer?

(a)  Animal fat                                    

(b)  Starch

(c)  Cellulose                                     

(d) Polyester

EXPLANATION: Polyester is a synthetic polymer made by the polymerization of units derived from the reaction of a diol and aromatic dicarboxylic acids.

(iv) Plastics are a pollution problem because many plastics:

(a)  Are made from petroleum

(b)  Are very inflammable

(c)  Burn to produce toxic fumes

(d)  Decompose to produce toxic products

EXPLANATION: When plastic materials are burned, they can release a variety of toxic substances into the air, contributing to air pollution. Some major pollutants produced are dioxins, furans, polycyclic aromatic hydrocarbons, volatile organic compounds & HCl etc.

(v) The fiber which is made from acrylonitrile as monomer:

(a)  PVC                                             

(b)  Rayon fiber

(c)  Acrylic fiber                                

(d) Polyester resin  

EXPLANATION: Acrylic fibers are synthetic fibers made from polymers derived from acrylonitrile, a petrochemical monomer. The main monomer used in the production of acrylic fibers is acrylonitrile. The process involves polymerization of acrylonitrile to form polyacrylonitrile (PAN), which is then spun into fibers.

(vi) A polymeric substance that is formed in the liquid state and then hardened to a rigid solid is called a:                    

(a)  Fiber                                           

(b)  Plastic

(c)  Varnish                                        

(d) Polyamide resin

EXPLANATION: Plastic is a synthetic material made from polymers, which are large molecules composed of repeating structural units. The preparation of plastic involves the polymerization of monomers. The polymeric substance begins as a liquid and undergoes a hardening process to transform into a rigid solid material. The transition from liquid to solid typically involves cooling or curing mechanisms.

(vii) Vegetable oils are:    

(a)  Unsaturated fatty acids

(b)  Glycerides of unsaturated fatty acids

(c)  Glycerides of saturated fatty acids

(d)  Essential oils obtained from plants

EXPLANATION: Vegetable oils are the triglycerides of unsaturated fatty acids because the extent of saturation is related to the melting point of the acyl glycerols. The greater the number of double bonds in fatty acid, the lower will the melting point of the oil and vice versa.

(viii) Which one of the following elements is not present in all proteins?     

(a)  Carbon                                        

(b)  Hydrogen

(c)  Nitrogen                                     

(d) Sulphur

EXPLANATION: Sulfur is generally present in most types of proteins, but some soluble globular proteins may have lower sulfur content compared to fibrous proteins. However, it’s essential to note that the absence of sulfur is not a defining characteristic of any protein type.

(ix) Which one of the following nitrogenous bases is not present in RNA? 

(a)  Cytosine           

(b)  Adenine           

(c)  Thymine           

(d)  Uracil

EXPLANATION: In RNA, Uracil nitrogen base is present instead of thymine.

(x) Which one of the following enzymes brings about the hydrolysis of fats?             

(a)  Urease             

(b)  Maltase            

(c)  Zymase            

(d)  Lipase

EXPLANATION: Lipase brings about the hydrolysis of fats because is directly involved in the digestion of fats into glycerol and fatty acids in small intestine of man.

(xi) The reaction between fat and NaOH is called:

(a)  Esterification                               

(b)  Hydrogenolysis

(c)  Fermentation                               

(d) Saponification

EXPLANATION: Saponification is the reaction between fat and NaOH to form soap.

(xii) Which one of the following statements about glucose and sucrose is incorrect?

(a)  Both are soluble in water

(b)  Both are naturally occurring

(c)  Both are carbohydrates

(d)  Both are disaccharides

EXPLANATION: Glucose is a monosaccharide, while sucrose is a disaccharide.

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