Question

Group 16 elements are called chalcogens i.e., ore forming elements (oxygen, sulphur, selenium etc.) because most of the ores are oxides and sulphides. Oxygen is gas where as other elements of group 16 are solids. Oxygen shows anomalous behaviour. Oxygen is diatomic where is sulphur exists as \(S_8\) which has crown shaped structure. It shows allotropy. Sulphur is present in onion and garlic that is why they have pungent smell. Sulphur is used for manufacture of sulphuric acid which is called ‘King of chemicals’, used in fertilizer, detergents, dyes and drugs. The following questions are multiple choice questions. Choose the most appropriate answer. 1) Group 16 elements are also known as a) Noble elements b) Halogens c) Pnictogens d) Chalcogens 2) Acidic character of hydrides of group 16 elements is in the order a) \(H_2\)O < \(H_2\)S < \(H_2\)Se < \(H_2\)Te b) \(H_2\)S < \(H_2\)Se < \(H_2\)Te < \(H_2\)O c) \(H_2\)O < \(H_2\)Se < \(H_2\)Te < \(H_2\)S d) \(H_2\)O < \(H_2\)S < \(H_2\)Te < \(H_2\)Se 3) Hybridisation of S in \(SF_4\) and geometry of \(SF_4\) are respectively a) \(sp^3\)d, trigonal pyramidal b) \(sp^3\)d, see saw c) \(sp^3\), tetrahedral d) \(dsp^2\), square planner 4) Which is not an acidic oxide? a) \(CO_2\) b) \(SO_2\) c) \(Na_2\)O d) \(Cl_2\)\(O_7\) 5) Which is not correct about allotropes of sulphur a) The stable form at room temperature is rhombic sulphur b) Monoclinic sulphur is stable above 369 K and transforms into rhombic sulphur below it c) At 369 K both the forms are stable d) Monoclinic sulphur is soluble in \(CS_2\) while rhombic sulphur not

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: The transition metals when exposed to oxygen at low and intermediate temperatures form thin, protective oxide films of up to some thousands of Angstroms in thickness. Transition metal oxides lie between the extremes of ionic and covalent binary compounds formed by elements from the left or right side of the periodic table. They range from metallic to semiconducting and deviate by both large and small degrees from stoichiometry. Since d electron bonding levels are involved, the cations exist in various valence states and hence give rise to a large number of oxides. The crystal structures are often classified by considering a cubic or hexagonal close-packed lattice of one set of ions with the other set of ions filling the octahedral or tetrahedral interstices. The actual oxide structures, however, generally show departures from such regular arrays due in part to distortions caused by packing of ions of different size and to ligand field effects. These distortions depend not only on the number of d-electrons but also on the valence and the position of the transition metal in a period or group. 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 on the basis of the above passage. 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. 1) Assertion: Cations of transition elements occur in various valence states Reason: Large number of oxides of transition elements are possible. 2) Assertion: Crystal structure of oxides of transition metals often show defects. Reason: Ligand field effect cause distortions in crystal structures. 3) Assertion : Transition metals form protective oxide films. Reason: Oxides of transition metals are always stoichiometric. 4) Assertion: CrO crystallises in a hexagonal close-packed array of oxide ions with two out of every three octahedral holes occupied by chromium ions. Reason: Transition metal oxide may be hexagonal close-packed lattice of oxide ions with metal ions filling the octahedral voids.

The properties of the solutions which depend only on the number of solute particles but not on the nature of the solute are called colligative properties. Relative lowering in vapour pressure is also an example of colligative properties. For an experiment, sugar solution is prepared for which lowering in vapour pressure was found to be 0.061 mm of Hg.(vapour pressure of water at \(20^\circ\)C is 17.5 mm of Hg). Answer the following MCQs by choosing the most appropriate options: (i) Relative lowering of vapour pressure for the given solution is- (a) 0.00348 (b) 0.061 (c) 0.122 (d) 1.75 (ii) The vapour pressure (mm of Hg) of Solution will be (a) 17.5 (b) 0.61 (c) 17.439 (d) 0.00348 (iii) Mole fraction of sugar in the solution is (a) 0.00348 (b) 0.9965 (c) 0.061 (d) 1.75 (iv) If weight of sugar taken is 5 g in 108 g of water then molar mass of sugar will be (a) 358 (b) 120 (c) 240 (d) 400 (v) The vapour pressure (mm of Hg) of water at 293 K when 25 g of glucose is dissolved in 450 g of water is (a) 17.2 (b) 17.4 (c) 17.120 (d) 17.02

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.

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: All real structures are three-dimensional structures. They can be obtained by stacking two dimensional layers one above the other while placing the second square close packed layer above the first we follow the same rule that was followed when one row was placed adjacent to the other. The second layer is placed over the first layer such that the spheres of the upper layer are exactly above there of the first layer. In his arrangement spheres of both the layers are perfectly aligned horizontally as well as vertically. A metallic element crystallise into a lattice having a ABC ABC pattern and packing of spheres leaves out voids in the lattice. 1) What type of structure is formed by this arrangement? (A) ccp (B) hcp (C) ccp/fcc (D) none of the above 2) Name the non-stoichiometric point defect responsible for colour in alkali metal halides. (A) Frenkel defect (B) Interstitial defect (C) Schottky defect (D) F-centres 3) What is the total volume of atoms in a face centred cubic unit cell of a metal? (r is atomic radius). (A) 16/3 \(πr^3\) (B) \(πr^3\) (C) 24/3 \(πr^3\) (D) 12/3 \(πr^3\) 4) Which of the following statements not true for the amorphous and crystalline solids? (A) Amorphous solids are isotropic and crystalline solids are anisotropic. (B) Amorphous solids are short range order and crystalline solids are long range order. (C) Amorphous solids melt at characteristic temperature while crystalline solids melt over a range of temperature. (D) Amorphous solids have irregular shape and crystalline solids have a geometrical shape.