Question

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.

The properties of dilute or ideal solutions which depend only upon the concentration of the solute in the solution and no other characteristics are known as colligative properties. There are in all four such properties i.e. relative lowering in vapour pressure, osmotic pressure, elevation in boiling point temperature and depression in freezing point temperature. All of them help in calculating the observed molar mass of the solute which is inversely proportional to the colligative property involved. Out of these, osmotic pressure may be regarded as the best for the determination of molecular mass of the solute. According to Van’t Hoff theory of dilute solution, π = CRT, where ‘π’ is the osmotic pressure while ‘C’ is the molar concentration of the solution. (i) When liquids A and B are mixed, hydrogen bonding occurs. The solutions will show: a) Positive deviation from Raoult’s law b) Negative deviation from Raoult’s law c) No deviation from Raoult’s law d) Slightly increase in volume (ii) The azeotropic mixture of water and HCl boils at \(108.5^\circ\)C when the mixture is distilled. It is possible to obtain: a) Pure HCl b) Pure water c) Pure water as well as pure HCl d) Neither HCl nor water in their pure states. (iii) On freezing an aqueous solution of sugar, the solid which starts separating out is: a. Sugar b. Ice c. Solution with the same composition d. Solution with different composition (iv) The value of osmotic pressure does not depend upon: a) Concentration of the solution b) Temperature of the solution c) Number of the particles of the solute present d) Structure of the solute particles (v) Effect of adding a non-volatile solute to a solvent is : a) to lower the vapour pressure b) to increase the freezing point c) to decrease the boiling point d) to decrease the osmotic pressure

Molecular Nitrogen \(N_2\) comprises about 78% by volume of Earth’s atmosphere. It occurs as Sodium nitrate, \(NaNO_3\)(chile saltpeter) & Potassium nitrate, \(KNO_3\)(Indian altpeter) in earth’s crust. Since nitrate are very soluble in water so these are not wide spread in the earth’s crust. Nitrogen is also an important constituent of amino acids, protein & nucleic acids in plants & animals. Nitrogen shows anomalous behavior from rest of the elements due to following reasons; Smaller size, high ionization enthalpy, high electronegativity & absence of d-orbital. It has unique ability to form p∏-p∏ multiple bonds with itself & with small size atoms like C & O as they have small size & high electronegativity. Heavier elements of this group do not form p∏-p∏ bonds as their atomic orbitals are so large & diffuse that they can’t have effective overlapping. Thus Nitrogen exists as diatomic molecules \(N_2\) with a triple bond. Consequently, its bond enthalpy (941.4 KJ \(mol^{-1}\)) is very high. P, As & Sb form only single bonds as P-P, As-As & Sb-Sb. Due to much bond enthalpy N is much less reactive than P. Single N-N bond is weaker than single P-P bond due to high interelectronic repulsion of the non bonding electrons, owing to small bond length. As a result, the catenation tendency is weaker in nitrogen. Hence nitrogen exists as gas while phosphorus exists as solid. Nitrogen can’t form d∏- d∏ bond due to absence of d- orbitals so it can’t expand its covalency beyond four as heavier members can. The following questions are multiple choice questions. choose the most appropriate answer. 1) Among group 15 elements which exists as gas at room temperature a) Arsenic b) Bismuth c) Nitrogen d) Phosphorous 2) The stability of +5 oxidation state decreases and that of +3 state increases down the group in group 15 elements due to a) inert pair effect b) decrease in ionisation enthalpy c) increase in size d) shielding effect 3) Nitrogen is restricted to a maximum covalency of 4 because of a) absence of d-orbitals b) presence of d-orbitals c) absence of s and p-orbitals d) none of the above 4) Extra pure \(N_2\) can be obtained by heating a) \(NH_3\) with CuO b) \(NH_4NO_3\) c) \(\left(NH_4\right)_2Cr_2O_7\) d) \(Ba\left(N_3\right)_2\) 5) Catenation tendency is weaker in nitrogen, because of a) single N–N bond is weaker b) single N–N bond is stronger c) ability to form pi bonds by N atoms d) none of the above

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

Read the passage given below and answer the following questions: Nucleophilic substitution reactions are of two types; substitution nucleophilic bimolecular (SN2) and substitution nucleophilic unimolecular (SN1) depending on molecules taking part in determining the rate of reaction. Reactivity of alkyl halide towards SN1 and SN2 reactions depends on various factors such as steric hindrance, stability of intermediate or transition state and polarity of solvent. SN2 reaction mechanism is favoured mostly by primary alkyl halide or transition state and polarity of solvent, SN2 reaction mechanism is favoured mostly by primary alkyl halide then secondary and then tertiary. This order is reversed in case of SN1 reactions. (i) Which of the following is most reactive towards nucleophilic substitution reaction? (a) \(C_6\)\(H_5\)Cl (b) \(CH_2\)=CHCl (c) \(ClCH_2\)\(CH=CH_2\) (d) \(CH_3\)CH=CHCl (ii) Isopropyl chloride undergoes hydrolysis by (a) SN1 mechanism (b) SN2 mechanism (c) SN1 and SN2 mechanism (d) neither SN1 nor SN2 mechanism (iii) Tertiary alkyl halides are practically inert to substitution by SN2 mechanism because of (a) insolubility (b) instability (c) inductive effect (d) steric hindrance (iv) Which of the following is the correct order of decreasing SN2 reactivity? (a) \(RCH_2\)X > \(R_2\)CHX > \(R_3\)CX (b) \(R_3\)CX > \(R_2\)CHX > \(RCH_2\)X (c) \(R_2\)CHX > \(R_3\)CX > \(RCH_2\)X (d) \(RCH_2\)X > \(R_3\)CX > \(R_2\)CHX (v) An organic molecule necessarily shows optical activity if it- a) contains asymmetric carbon atoms b) is non-polar c) is non-superimposable on its mirror image d) is superimposable on its mirror image

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