Question

Group 18 elements are called noble gases and not inert gases because compounds of Kr, Xe and Rn have been prepared. Their general electronic configuration is \(ns^2\)\(np^6\) except He(\(1s^2\) ). They have highest ionisation enthalpy and positive electron gain enthalpy due to stable electronic configuration. Helium is found in sun and stars. Noble gases have low boiling points due to weak van der Waals’ forces of attraction. Xenon forms \(XeF_2\), \(XeF_4\), \(XeF_6\), \(XeOF_4\), \(XeO_3\), \(XeO_2\)\(F_2\), their structures can be drawn on bases of VSEPR theory. Helium is mixed with oxygen by deep sea divers to avoid pain. Neon is used in coloured advertising lights. Argon is used in bulbs as inert gas. Kr and Xe are used in high efficiency lamps, head light of cars. Radon is radioactive formed by a-decay of Radium 226 88Ra Argon is most abundant (0.9%) noble gas in atmosphere. The following questions are multiple choice questions. Choose the most appropriate answer. 1) What are the elements in group 18 (the far right) of the periodic table called? a) Alkali metals b) Alkaline earth metals c) Halogens d) Noble gases 2) Out of (i) \(XeO_3\) (ii) \(XeOF_4\) and (iii) \(XeF_6\) , the molecules having the same number of lone pairs on Xe are - a) (i) and (ii) only b) (i) and (iii) only c) (ii) and (iii) only d) (i) , (ii) and (iii) 3) Which one has linear shape? a) \(XeF_2\) b) \(XeF_4\) c) \(XeF_6\) d) \(XeO_3\) 4) Which of the outer electronic configuration represent Argon? a) \(ns^2\)\(np^4\) b) \(ns^2\)\(np^3\) c) \(ns^2\)\(np^6\) d) \(ns^1\)\(np^6\) 5) Which of the following statement is false? a) Radon is obtained from the decay of radium b) Helium is an inert gas c) Xenon is the most reactive among the rare gases d) The most abundant rare gas found in the atmosphere is helium

Read the passage given below and answer the following questions: When a protein in its native form, is subjected to physical changes like change in temperature or chemical changes like change in pH, the hydrogen bonds are disturbed. Due to this, globules unfold and helix get uncoiled and protein loses its biological activity. This is called denaturation of protein. The denaturation causes change in secondary ann tertiary structures but primary structures remain intact. Examples of denaturation of protein are coagulation of egg white on boiling, curdling of milk, formation of cheese when an acid is added to milk. Choose the most appropriate answer: i) Mark the wrong statement about denaturation of proteins. a) The primary structure of the protein does not change. b) Globular proteins are converted into fibrous proteins. c) Fibrous proteins are converted into globular proteins. d) The biological activity of the protein is destroyed. ii) Which structure{s) of proteins remains(s) intact during denaturation process? (a) Both secondary and tertiary structures (b) Primary structure only (c) Secondary structure only (d) Tertiary structure only iii) a-helix a n d β - pleated structures of proteins are classified as (a) primary structure (b) secondary structure (c) tertiary structure (d) quaternary structure. (iv) Secondary structure of protein refers to a) mainly denatured proteins and structure of prosthetic groups. b) three-dimensional structure, especially the bend between. amino acid residues that are distant from each other in the polypeptide chain. c) linear sequence of amino acid residues in the polypeptide chain. d) regular folding patterns of continuous portions of the polypeptide chain.

An organic compound A having molecular formula \(C_6\)\(H_6\)O turn blue litmus solution into red but does not react with sodium bicarbonate, but when treated with bromine water then form a white ppt of compound B. when compound A react with chloroform in presence of aqueous caustic soda solution at 340K then form two compound C and D. When compound A treated with caustic soda then form compound E compound E when treated with methyl halide then form compound F. Read the above passage carefully and answer the following questions: (i) The name of compound is: (a) 2-methyl propene-2-ol (b) 2-methyl phenol (c) 2,4,6-tribromophenol (d) Butane 1-ol (ii) Which are isomers of each other (a) A and C (b) B and C (c) C and D (d) D and E (iii) The IUPAC name of compound F is (a) Anisole (b) Methoxybenzene (c) Salicylaldehyde (d) 2-methyl propene-2-ol (iv) When compound E treated with ethyl iodide then ...... form. (a) Ehoxybenzene (b) Ethoxy hexane (c) Propoxypropane (d) Benzaldehyde (v) On oxidation with sodium dichromate and conc \(H_2\)\(SO_4\) phenol gives (a) Benzaldehyde (b) p-Benzoquinone (c) o-Benzoquinone (d) m-benzoquinone

Read the passage given below and answer the following questions: In an ideal crystal, there must be regular repeating arrangement of the constituting particles and its entropy must be zero at absolute zero temperature. However, it is impossible to obtain an ideal crystal and it suffers from certain defects called imperfections. In pure crystal, these defects arises either due to disorder or dislocation of the constituting particles from the normal positions or due to the movement of the particles even at absolute zero temperature. Such defects increase with rise in temperature. In addition to these certain defects arise due to the presence of some impurities. Such defects not only modify the existing properties of the crystalline solids but also impart certain new characteristics to them. Answer the following MCQs by choosing the most appropriate options: 1) AgCl is crystallized from molten AgCl containing a little \(CdCl_2\). The solid obtained will have (a) cationic vacancies equal to number of \(Cd^{2+}\) ions incorporated. (b) cationic vacancies equal to double the number of \(Cd^{2+}\) ions. (c) anionic vacancies. (d) neither cationic nor anionic vacancies. 2) Lattice defect per \(10^{15}\) NaCl is 1. What is the number of lattice defects in a mole of NaCl? (a) 6.02 × \(10^{23}\) (b) 6.02 × \(10^8\) (c) \(10^{14}\) (d) None of these 3) The ionic substances in which the cation and anion are of almost similar size shows (a) non-stoichiometric defect (b) Schottky defect (c) Frenkel defect (d) all of these 4) Which of the following gives both Frenkel and Schottky defect? (a) AgCl (b) CsCl (c) KCl (d) AgBr

Read the passage given below and answer the following questions: Phenol contains -OH group directly attached to carbon atoms of an aromatic system \(C_6\)\(H_5\)OH in phenol the group is attached to \(sp^2\) hybridised carbon of aromatic ring. The carbon oxygen bond length is 1:36 pm in phenol is slightly less than that in in methanol this is due to first point partial double bond character on account of the conjugation of unshared electron pair of oxygen with the aromatic ring s point \(sp^3\) hybridised state of carbon to which oxygen is attached it can be prepared by various means or methods. Some important methods are alkali fusion of sulphonates, hydrolysis of diazonium salts decarboxylation of salicylic acid and from Grignard reagent, it is prepared from Dow's process and from cumene. Aerial oxidation of human produce cumene peroxide which on hydrolysis produce phenol and acetone. In the following questions a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices. (a) Both assertion and reason are true and the reason is the correct explanation of assertion. (b) Both assertion and reason are true but the reason is not the correct explanation of assertion. (c) Assertion is true but reason is false. (d) Assertion is false but reason is true. (i) Assertion: C-O bond length in phenol is less than C-O bond length in ethanol. Reason: In phenol carbon atom is \(sp^2\) hybridize while in ethanol carbon atom is \(sp^3\) hybridised. (ii) Assertion: p-nitrophenol is more acidic than phenol. Reason: Nitro group helps in the stabilisation of the phenoxide ion by dispersal of negative charge due to resonance. (iii) Assertion: Phenol is prepared by the reaction of chlorobenzene with caustic soda at 623K and 300 atm pressure. Reason: The substitution of chorine atom from chlorobenzene is difficult due to resonance. (iv) Assertion: Methanol is less acidic than phenol. Reason: Due to resonance phenate ion become more stable. (v) Assertion: On nitration phenol forms 2-nitrophenol and 4- nitrophenol. Reason: The presence of –OH group in phenols activates the aromatic ring towards electrophilic substitution and directs the incoming group to ortho and para positions.

Read the passage given below and answer the following questions: Alkyl halides are prepared by the free radical halogenation of alkanes, addition of halogen acids to alkenes, replacement of -OH group of alcohols with halogens using phosphorus halides, thionyl chloride or halogen acids. Aryl halides are prepared by electrophilic substitution to arene. Fluorine and iodides are best prepared by halogen exchange method. These compounds find wide applications in industry as well as in day-to-day life. These compounds are generally used as solvents and as starting material for the synthesis of a large number of organic compounds. (i) The best method for the conversion of an alcohol into analkyl chloride is by treating the alcohol with (a) \(PCl_5\) (b) dry HCl in the presence of anhydrous \(ZnCl_2\) (c) \(SOCl_2\) in presence of pyridine (d) None of these (ii) The catalyst used in the preparation of an alkyl chloride bythe action of dry HCl on an alcohol is (a) anhydrous \(AlCl_3\) (b) \(FeCl_3\) (c) anhydrous \(ZnCl_2\) (d) Cu (iii) An alkyl halide reacts with metallic sodium in dry ether. The reaction is known as : (a) Frankland’sreaction (b) Sandmeyer’sreaction (c) Wurtz reaction (d) Kolbe’s reaction (iv) Fluorobenzene (\(C_6\)\(H_5\)F) can be synthesized in the laboratory (a) by direct fluorination of benzene with \(F_2\) gas (b) by reacting bromobenzene with NaF solution (c) by heating phenol with HF and KF (d) from aniline by diazotisation followed by heating thediazonium salt with \(HBF_4\) (v) When 2-bromobutane reacts with alcoholic KOH, thereaction is called (a) halogenation (b) chlorination (c) hydrogenation (d) dehydrohalogenation

The sequence of bases along the DNA and RNA chain establishes its primary structure which controls the specific properties of the nucleic acid. An RNA molecule is usually a single chain of ribose-containing nucleotide. On the basis of X-ray analysis of DNA, J.D., Watson and F.H.C. CYST (shared noble prize in 1962) proposed a three dimensional secondary structure for DNA. DNA molecule is a long and highly complex, spirally twisted, double helix, ladder like structure. The two polynucleotide chains or strands are linked up by hydrogen bonding between the nitrogenous base molecules of their nucleotide monomers. Adenine (purine) always links with thymine (pyrimidine) with the help of two hydrogen bonds and guanine (purine) with cytosine (pyrimidine) with the help of three hydrogen bonds. Hence, the two strands extend in opposite directions, i.e., are antiparallel and complimentary. In these questions (Q. No. i-iv), a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices. a) Assertion and reason both are correct statements and reason is correct explanation for assertion. b) Assertion and reason both are correct statements but reason is not correct explanation for assertion. c) Assertion is correct statement but reason is wrong statement d) Assertion is wrong statement but reason is correct statement. i) Assertion - DNA molecules and RNA molecules are found in the nucleus of a cell. Reason : There are two types of nitrogenous bases, purines and pyrimidines. Adenine (A) and guanine (G)are substituted purines; cytokine (C), thymine (T) arid uracil (U) are substituted pyrimidines. ii) Assertion .- In both DNA and RNA, heterocyclic base and phosphate ester linkages are at C- 1’ and C-5’respectively of the sugar molecule. Reason : Nucleotides and nucleosides mainly differ from each other in presence of phosphate units. iii)Assertion .- The backbone of RNA molecule is a linear chain consisting of an alternating units of heterocylic base, D-ribose and a phosphate. Reason : The segment of RNA which acts as the instruction manual for the synthesis of protein is ribose. iv) Assertion.- In DNA, the complementary bases are, adenine and guanine; thymine and cytosine. Reason : The phenomenon of mutation is chemical change in DNA molecule.