P- BLOCK ELEMENTS Group-15 Elements Group-16 Elements. 17th group elements 18 th group elements

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1 P- BLOCK ELEMENTS Group-15 Elements Group-16 Elements 17th group elements 18 th group elements

2 1. Which of the following elements does not belong to group 15? a) Nitrogen b) phosphorus c) Arsenic d) Tin Group -15 elemets are; N, P, As,Sb & Bi. Tin,Sn:Group-14 element. Answ: (d)

3 2. Which is the correct order regarding the boiling points of hydrides of Group 15? a) NH 3 > PH 3 > AsH 3 b) NH 3 < PH 3 < AsH 3 c) NH 3 > PH 3 < AsH 3 d) NH 3 < PH 3 > AsH 3 B. pt. increases with strength of intermolecular forces, which is in the order: PH 3 < AsH 3 < SbH 3 < NH 3 < BiH 3. Answ: c)

4 3. Covalency of nitrogen never exceeds a) 3 b) 4 c) 5 d) 6 Nitrogen has only four orbitals in its valence shell, all of which can be used for bond formation. No d- orbitals are available. Answ: (b)

5 4. Which of the following orders regarding H E H bond angle of the hydrides of group 15 elements is correct? a) H-N-H > H-P-H> H-As-H b) H N H < H P H< H As H c) H-N-H > H-P-H< H-As-H d) H N H < H P H> H As H As electronegativity C.A dereases bond angle decreases. Answ: (a)

6 5. Which of the following oxides of nitrogen are obtained on heating Ammonium nitrate? a) N 2 O b) NO c) NO 2 d) N 2 O 5 NH 4 NO 3 heat N 2 O +2H 2 O. Answ: (a)

7 6. Orthophosphorous acid is a a) monobasic acid b) dibasic acid c) tribasic acid d) tetrabasic acid.

8 H 3 PO 4 has 2 P OH bonds. The H atoms bonded to O are responsible for the basicity of the acid. Answ: (b)

9 7. Concentrated nitric acid oxidizes iodine to a) HI b) HIO 3 c) NH 4 I d) HIO 4 I 2 +10HNO 3 2HIO 3 +10NO 2 +4H 2 O Answ: (b)

10 8. Which of the elements of Group 16 has maximum tendency of catenation? a)oxygen b)sulphur c)selenium d)tellurium S S bond is strongest among group 16 elements. So it shows maximum extent of catenation. Answ: (b)

11 9. Which of the following hydrides of Group 16 has the lowest boiling point? a) H 2 O b)h 2 S c)h 2 Se d)h 2 Te B. pt. increases with strength of intermolecular forces. H 2 O has strong intermolecular hydrogen bonds. In case of H 2 S, H 2 Se &H 2 Te, weak dispersion forces : increases with M. Answ: (b)

12 10. Which of the following bonds has the highest bond energy? a) O O b) S S c) Se Se d) Te Te O O bond though shortest, but weak due to strong lone pair- lone pair repulsions due to the small size of O atoms. Answ: (b)

13 11. Which of the following is the weakest acid? a) H 2 S b) H 2 Se c) H 2 O d) H 2 Te H 2 O has the strongest bond which doesn t break readily to release H +. So it is the weakest acid. Answ: (c)

14 12. In the manufacture of sulphuric acid by the contact process, SO 3 is not added to water directly to form H 2 SO 4 because a) the reaction does not go to completion. b) the reaction is exothermic. c) the reaction is quite slow. d) SO 3 is insoluble in water. Ans (b)

15 13. Which of the following forms of sulphur is stable at room temperature and 1 atmospheric pressure? a) Amorphous b) hexagonal c) Monoclinic d) Orthorhombic Rhombic sulphur ( α sulphur), Above 369K,monoclinic form is stable. Answ:( d)

16 14. Sulphur dioxide is a strong reducing agent. However, it can also act as an oxidizing agent. Which of the following reactions shows its oxidizing natures? a) Bleaching flower petals. b) Decolorizing of acidified KMnO 4 solution. c) Reaction of H 2 S to give sulphur. d) Turning acidified dichromate paper green. Answ: (c)

17 15. When conc. H 2 SO 4 is added to NaCl a) Cl is released as volatile HCl. b) Cl is oxidized to Cl 2. c) NaCl is dehydrated. d) NaCl is neutralized by H 2 SO 4. Due to low volatility of H 2 SO 4 2NaCl + H 2 SO 4 2HCl + Na 2 SO 4 Answ:( a)

18 16. Which of the following orders of bond dissociation enthalpy of halogens is correct? a) F F > Cl Cl > Br Br b) F F < Cl Cl < Br Br c) F F > Cl Cl < Br Br d) F F < Cl Cl > Br Br Small size of F; l.p l.p repulsion Answ: (d)

19 17. Which of the following orders of melting point of hydrides of halogens is correct? a) HF > HCl > HBr b) HF < HCl < HBr c) HF > HCl < HBr d) HF < HCl > HBr In HF Strong H-bonding, in others weak dispersion forces. Answ: (c)

20 18. The structure of IF 7 is a) Planar b) Distorted octahedral c) Pentagonal bipyramidal d) Distorted trigonal pyramidal Here 7 bond pairs & no lone pairs; Hence according to VSEPR pentagonal bipyramidal. Answ: (c)

21 19. The anhydride of HClO 4 is a) ClO -- 4 b) Cl 2 O 7 c) ClO 2 d) ClO 3 Removal of one molecule of H 2 O from two molecules of HClO 4 gives Cl 2 O 7 Answ: (b)

22 20. Which of the following interhalogens does not exist? a) ClF b) ClF 2 c) ClF 3 d)clf 5 The inter halogen compounds have a general molecular formula of XX 2n+1 (n= 0, 1, 2 or 3). ClF 2 doesn t fit to in to it. Answ(b)

23 21. The order of Acidic strength of oxo acids of chlorine is a) HClO < HClO 2 < HClO 3 < HClO 4 b) HClO > HClO 2 > HClO 3 > HClO 4 c) HClO > HClO 2 > HClO 3 < HClO 4 d) HClO < HClO 2 < HClO 3 > HClO 4 Acidic strength increases with Oxdn state of Cl Answ: (a)

24 22. The structure of XeO 4 is a) square planar b) tetrahedral c) pentagonal with one lone pair of electrons d) octahedral with two lone pairs No l.p but 4 b.p are there ; structure is tetrahedral. Answ: (a)

26 23. The ionization energy of Xe Xe+ + e is very close to that of a)n 2 N e b) O 2 O e c) C 2 C e d) B 2 B e Answ: (b)

27 24. The number of electron pairs around Xe in XeF 4 are a) 3 b) 4 c) 5 d) 6 In XeF 4, out of 8 electrons of Xe 2 l.p & 2b.p: & 2 b.p of F is also presnt. Total 6 pairs. Answ: (b)

29 25. When chlorine reacts with cold and dilute solution of sodium hydroxide, the products obtained are a) Cl + ClO b) Cl + ClO 2 c) Cl + ClO 3 d) Cl + ClO 4 2 NaOH + Cl 2 NaCl + NaOCl +H 2 O. Answ: (a)

30 26. The structure of interhalogen AX 3 is a) Triangular planar b) Pyramidal c) T-shaped with two lone pairs of electrons at two equilateral positions d) Tetrahedral with single electron. AX 3 contains 3 b.p and 2l.p, hence structure is T-shaped with two lone pairs of electrons at two equilateral positions Answ: (c)

31 27. Which of the following represents hypohalous acid? a) HOX b) HXO 2 c) HXO 3 d) HXO 4 Answ: (a)

32 28. Which of the following statements regarding ozone is not true? a) Ozone is an allotrope of oxygen. b) The ozone layer protects the earth s surface from an excessive concentration of harmful ultraviolet radiation. c) The conversion of oxygen into ozone is an exothermic process. d) Ozone is much more powerful oxidizing agent than molecular oxygen. Answ: (c)

33 29. The dimerization of NO 2 is accompanied by a) an increase in paramagnetism b) a decrease in paramagnetism c) no change in paramagnetism d) a darkening in colour Dimerisation of NO 2 is : 2NO 2 N 2 O 4. The odd electron of NO 2 gets paired up & decrease the paramagnetism. Answ: (b)

34 30. Phosphine may be produced by adding water to a) Ca 3 P 2 b) P 4 O 6 c) P 4 O 10 d) HPO 3 Ca 3 P 2 + 6H 2 O 3 Ca (OH) PH 3 Answ: (a)

35 31. Which of the following possesses pπ-d π bonding? a) NO 3 b) BO 3 3- c) SO 3 2- d) CO 3 2- SO 3 2- is O- S=O O π bond is d-orbitals of S & p- orbitals of O N, B, & C do not have d-orbitals Answ: c)

36 32. Which of the following is the order of compounds is according to the decreasing order of the oxidation state of nitrogen? a) HNO 3,NO,NH 4 Cl,N 2 b) HNO 3, NO, N 2, NH 4 Cl c) HNO 3, NH 4 Cl, NO, N 2 d) NO, HNO 3, NH 4 Cl,N 2 O.S of N in HNO 3 : +5, NO : +2, N 2 : 0, NH 4 Cl: -3 Answ: (b)

37 33. Smallest bond angle is in a) NCl 3 b) AsCl 3 c) SbCl 3 d) PCl 3 Down the group at.size of central atom increases; bond angle decreases. Answ: (c)

38 34. The gas used for inflating aero plane tyres is a) H 2 b)he c) N 2 d) Ar He is light & non flammable Answ: (b)

39 35. Xenon best reacts with a) F 2 b) O 2 c) N 2 d) Cl 2 F is most electronegative element Answ: (c) 36. Among known interhalogens the maximum number of halogen atoms in a molecule, is a) 8 b) 7 c) 5 d) 6 Answ: (a)

40 37. The halogen(s) which can displace iodine from KI is/ are a) F b) Cl c) Br d) All these Answ: (d) 38. Elements of which one of the following groups will form anions most readily? a) Group -16 b) Group -15 c) Group -17 d) Group -18 Answ: (c)

41 39. Bleaching action of chlorine is due to a) Oxidation b) reduction c) Hydrolysis d) hydration Chlorine water HCl+HOCl [O] Answ: (a)

42 40. Among the following molecules i) Xe O 3 ii) XeO F 4 iii) Xe F 6, Those having 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) only Answ: (d)

44 41. Which of the following is not correct? a) Xe O 3 Has four σ and four π bonds. b) The hybridisation of Xe in Xe F 4 is sp3d2. c) Among the noble gases the occurrence of Ar is highest in air. d) Liquid he is used in cryogenic liquids. Answ: (a)

45 42. Xe F 6 on complete hydrolysis gives a) Xe b) Xe O 2 c) Xe O 3 d) Xe O 4 Xe F H 2 O 6HF + Xe O 3 Answ: (c )

46 43. Which of the following sets has strongest tendency to form anions? a) Ga,In,Tl b) Na,Mg, Al c) N,O,F d) V,Cr, Mn. N,O,F has highest electron affinity: Forms anions redily. Answ: (c )

47 44. Which of the following bonds will be most polar? a) N-Cl b) O-F c) N-F d) N-N Greater the electronegative difference more is the polarity. Answ: (c )

48 45. Chorine gas is dried over a) Quick lime b) caustic soda c) Caustic potash d) conc H 2 SO 4 conc H 2 SO 4, All others reacts with chlorne. Answ: (d )

49 46. When cold NaOH reacts with which of the following is formed? a) NaClO b) NaClO 2 c) NaClO 3 d) None 2NaOH+ Cl 2 NaCl + NaOCl + H 2 O Answ: (a)

50 47. A colour less gas with smell of rotten fish is a) H 2 S b) PH 3 c) SO 2 d) None of these. Answ: (b)

51 48. On heating O 3, its volume becomes a) Half b) double c) 2/3 times d) 3/2 times. 2O 3 3O 2 2vol 3 vol. Answ: (d)

52 49. Which on of the following is not oxidised by ozone? a) FeSO 4 b) KMnO 4 c) KI d) K 2 MnO 4 Mn in has highest oxidationstate +7; furter oxidation is not possible. Answ: (b)

53 50. Phosphine is prepared in the laboratory by a) Heating P in a current of H 2 b) Heating yellow P with aq KOH c) Heating red P with aq KOH d) treating yellow P with NH 3 Answ: (b)

54 51. Helium is added to oxygen used by sea divers because it is a) Practically not soluble in blood at high pressure. b) Lighter than nitrogen c) Readily miscible with oxygen d) Less poisonous than nitrogen. Answ: (a)

55 52. Compound(s) possible with xenon is/are a) Oxides b) flurides c) Oxyflurides d) All of these. Xe forms compounds with highly electronegative elements. Answ: (d)

56 53. Sulphuric acid behaves as a) A strong acid b) An oxidising agent c) Adehydrating agent d) All of these Answ: (d) 54. Among halogens electron gain enthalpy is maximum in a) F b) I c) Br d) Cl Answ: (d)

57 55. The ammonia molecule a) Triangular planar b)triangular bipyramidal c) Regular tetrahedron with bond angle 109 o 28 d) Trigonal pyramidal Answ: (d)

58 56. With excess water PCl 5 gives a) H 3 PO 4 + HCl b) H 3 PO 3 + HCl c) H 3 PO 2 + HCl d) H 4 P 2 O 7 + HCl PCl 5 +4 H 2 O H 3 PO 4 + 5HCl Answ: (a)

59 57. The catalyst used in the contact process is a) Fe 2 O 3 b) V 2 O 5 c) SO 3 d) Ag 2 O Answ: (b)

60 58. Which of the following is a radioactive halogen? a) Cl b) Br c) I d) At Answ: (d)

PRADEEP SHARMA INSTITUTE OF COMPETITIVE STUDIES ( PICS INSTITUTE )

PRADEEP SHARMA INSTITUTE OF COMPETITIVE STUDIES ( PICS INSTITUTE ) I. Account for the following: 1. Nitrogen is not very reactive at room temperature. 2. Maximum covalency of nitrogen is 4. 3. Nitrogen does not form any pentahalide. 4. S2 formed at higher temperatures