P- BLOCK ELEMENTS •Group-15 Elements •Group-16 Elements

• 17th group elements

•18 th group elements

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)

2. Which is the correct order regarding the boiling points of hydrides of Group 15? a) NH3> PH3> AsH3 b) NH3< PH3< AsH3

c) NH3> PH3< AsH3 d) NH3< PH3> AsH3

B. pt. increases with strength of intermolecular forces, which is in the order: PH3< AsH3< SbH3< NH3< BiH3. Answ: c)

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)

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)

5. Which of the following oxides of nitrogen are obtained on heating Ammonium nitrate? a) N2O b) NO c) NO2 d) N2O5

NH4NO3 heat N2O +2H2O. Answ: (a)

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

H3PO4 has 2 P—OH bonds. The H atoms bonded to O are responsible

for the basicity of the acid.

Answ: (b)

7. Concentrated nitric acid oxidizes iodine to a) HI b) HIO3 c) NH4I d) HIO4

I2 +10HNO3 2HIO3 +10NO2 +4H2O Answ: (b)

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)

9. Which of the following hydrides of Group 16 has the lowest boiling point? a) H2O b)H2S c)H2Se d)H2Te B. pt. increases with strength of intermolecular forces. H2O has strong intermolecular hydrogen bonds. In case of H2S, H2Se &H2Te, weak dispersion forces : increases with M. Answ: (b)

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)

11. Which of the following is the weakest acid? a) H2S b) H2Se c) H2O d) H2Te H2O has the strongest bond which doesn’t break readily to release H+. So it is the weakest acid. Answ: (c)

12. In the manufacture of sulphuric acid by the contact process, SO3 is not added to water directly to form H2SO4 because a) the reaction does not go to completion. b) the reaction is exothermic. c) the reaction is quite slow. d) SO3 is insoluble in water.

Ans (b)

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)

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 KMnO4 solution. c) Reaction of H2S to give sulphur. d) Turning acidified dichromate paper green.

Answ: (c)

15. When conc. H2SO4 is added to NaCl a) Cl— is released as volatile HCl. b) Cl— is oxidized to Cl2. c) NaCl is dehydrated. d) NaCl is neutralized by H2SO4. Due to low volatility of H2SO4 2NaCl + H2SO4 2HCl + Na2SO4

Answ:( a)

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)

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)

18. The structure of IF7 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)

19. The anhydride of HClO4 is a) ClO4

-- b) Cl2O7

c) ClO2 d) ClO3

Removal of one molecule of H2O from two molecules of HClO4 gives Cl2O7

Answ: (b)

20. Which of the following interhalogens does not exist? a) ClF b) ClF2 c) ClF3 d)ClF5

The inter halogen compounds have a general molecular formula of XX’2n+1 (n= 0, 1, 2 or 3). ClF2 doesn’t fit to in to it.

Answ(b)

21. The order of Acidic strength of oxo acids of chlorine is a) HClO < HClO2 < HClO3 < HClO4 b) HClO > HClO2 > HClO3 > HClO4 c) HClO > HClO2 > HClO3 < HClO4 d) HClO < HClO2 < HClO3 > HClO4

Acidic strength increases with Oxdn state of Cl

Answ: (a)

22. The structure of XeO4 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)

23. The ionization energy of Xe Xe+ + e—is very close to that of a)N2 N2

+ + e— b) O2 O2+ + e—

c) C2 C2+ + e— d) B2 B2

+ + e—

Answ: (b)

24. The number of electron pairs around Xe in XeF4 are a) 3 b) 4 c) 5 d) 6 In XeF4, out of 8 electrons of Xe 2 l.p &

2b.p: & 2 b.p of F is also presnt . Total 6 pairs.

Answ: (b)

25. When chlorine reacts with cold and dilute solution of sodium hydroxide, the products obtained are a) Cl— + ClO— b) Cl—+ ClO2

— c) Cl—+ ClO3

— d) Cl— + ClO4—

2 NaOH + Cl2 NaCl + NaOCl +H2O. Answ: (a)

26. The structure of interhalogen AX3 is a) Triangular planar b) Pyramidal c) T-shaped with two lone pairs of electrons at two equilateral positions d) Tetrahedral with single electron. AX3 contains 3 b.p and 2l.p, hence structure is T-shaped with two lone pairs of electrons at two equilateral positions Answ: (c)

27. Which of the following represents hypohalous acid? a) HOX b) HXO2 c) HXO3 d) HXO4

Answ: (a)

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)

29. The dimerization of NO2 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 NO2 is : 2NO2 N2O4. The odd electron of NO2 gets paired up & decrease the paramagnetism. Answ: (b)

30. Phosphine may be produced by adding water to a) Ca3P2 b) P4O6 c) P4O10 d) HPO3

Ca3P2 + 6H2O 3 Ca (OH)2+ 2 PH3

Answ: (a)

31. Which of the following possesses pπ-d π bonding? a) NO3

— b) BO33-

c) SO32- d) CO3

2-

SO32- 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)

32. Which of the following is the order of compounds is according to the decreasing order of the oxidation state of nitrogen? a) HNO3 ,NO,NH4Cl,N2 b) HNO3 , NO, N2 , NH4Cl c) HNO3 , NH4Cl , NO, N2

d) NO, HNO3 , NH4Cl,N2

O.S of N in HNO3 : +5, NO : +2, N2 : 0, NH4Cl: -3 Answ: (b)

33. Smallest bond angle is in a) NCl3 b) AsCl3

c) SbCl3 d) PCl3

Down the group at.size of central atom

increases; bond angle decreases. Answ: (c)

34. The gas used for inflating aero plane tyres is a) H2 b)He c) N2 d) Ar He is light & non flammable Answ: (b)

35. Xenon best reacts with a) F2 b) O2 c) N2 d) Cl2

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)

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)

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

40. Among the following molecules i) Xe O3 ii) XeO F4 iii) Xe F6, 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)

41. Which of the following is not correct? a) Xe O3 Has four σ and four π bonds. b) The hybridisation of Xe in Xe F4 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)

42. Xe F6 on complete hydrolysis gives a) Xe b) Xe O2

c) Xe O3 d) Xe O4

Xe F6 + 3 H2O 6HF + Xe O3

Answ: (c )

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 )

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 )

45. Chorine gas is dried over a) Quick lime b) caustic soda c) Caustic potash d) conc H2SO4

conc H2SO4, All others reacts with chlorne.

Answ: (d )

46. When cold NaOH reacts with which of the following is formed? a) NaClO b) NaClO2 c) NaClO3 d) None

2NaOH+ Cl2 NaCl + NaOCl + H2O

Answ: (a)

47. A colour less gas with smell of rotten fish is a) H2S b) PH3 c) SO2 d) None of these.

Answ: (b)

48. On heating O3,its volume becomes a) Half b) double c) 2/3 times d) 3/2 times.

2O3 3O2 2vol 3 vol.

Answ: (d)

49. Which on of the following is not oxidised by ozone? a) FeSO4 b) KMnO4

c) KI d) K2MnO4

Mn in has highest oxidationstate +7; furter oxidation is not possible.

Answ: (b)

50. Phosphine is prepared in the laboratory by a) Heating P in a current of H2

b) Heating yellow P with aq KOH c) Heating red P with aq KOH d) treating yellow P with NH3

Answ: (b)

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)

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)

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)

55. The ammonia molecule a) Triangular planar b)triangular bipyramidal c) Regular tetrahedron with bond angle 109o28’ d) Trigonal pyramidal

Answ: (d)

56. With excess water PCl5 gives a) H3PO4 + HCl b) H3PO3 + HCl

c) H3PO2 + HCl d) H4P2O7 + HCl

PCl5 +4 H2O H3PO4 + 5HCl Answ: (a)

57. The catalyst used in the contact process is a) Fe2O3 b) V2O5 c) SO3 d) Ag2O

Answ: (b)

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

Answ: (d)