P – BLOCK ELEMENTS MCQs – 3

1) Nitrogen is a relatively inactive element because
a) Its atom has a stable electronic configuration
b) It has a low atomic radius
c) Its electronegativity is fairly high
d) The dissociation energy of its molecule is fairly high

2) Which one of the following substances is used in the laboratory for a fast drying of neutral gases?
a)
b) Active charcoal
c)
d)

3) When ammonia is passed over heated CuO, it is oxidised to
a)
b)
c)
d)

4) One would expect a proton to have a very large
a) Charge
b) lonization potential
c) Hydration energy
d) Radius

5) The ozone molecule is
a) Paramagnetic
b) Linear
c) Diamagnetic
d) Can be represented by a single structure

6) Pure nitrogen can be prepared from
a)
b)
c)
d)

7) Ozone belongs to which group of the periodic table?
a) 14
b) 15
c) 16
d) None of the above

8) Nitrogen gas is absorbed by
a) Aluminium carbide
b) Calcium carbide
c) Ferrous sulphate
d) Calcium hydroxide

9) Hydrogen at room temperature contains
a) 25% Ortho + 75% para
b) 25% Para + 75% ortho
c) 50% Ortho + 50% para
d) 66% Ortho + 34% para

10) Among the following oxides, the one which is most basic is
a) Zinc oxide
b) Magnesium oxide
c) Aluminium oxide
d) Nitrogen pentoxide

11) Which of the following substances will react with nitrogen when hot ?
a) Phosphorus
b) Lime water
c) Calcium chloride
d) Magnesium

12) Which of the following is a true peroxide?
a)
b)
c)
d)

13) Which of the following is/are amphoteric: BeO, SnO2 ?
a) BeO only
b)
c) Both
d) Neither

14) The gas used for sterilising water is
a)
b)
c)
d)

15) The process used to manufacture nitric acid is the
a) Solvay process
b) Ostwald process
c) Hall process
d) Haber process

16) NH3 has a much higher b.p. than PH3 because
a)
b)
c)
d)

17) There is no O – O bond in
a)
b)
c)
d)

18) The oxide insoluble in water is
a)
b)
c)
d)

19) About 20 km above the earth there is an ozone layer. Which one of the following statements about ozone and the ozone layer is true
a) The o\zone layer is beneficial to us because ozone cuts out the ultraviolet radiation of the sun
b) The conversion of ozone to oxygen is an endothermic reaction
c) Ozone has a triatomic linear molecule
d) The ozone layer is harmful to us because it cuts out radiation useful for photosynthesis

20) When SO2 gas is passed through cupric chloride solution
a) The solution becomes colourless, but no precipitate is formed
b) A white precipitate is formed, but no colour change.
c) No change takes place
d) the solution becomes colourless and a white precipitate is formed

21) Which of the following statements about white phosphorus are not true ?
a) It phosphoresces in air
b) It burns when heated in air
c)
d) It can be stored in contact with air

22) Which statement is correct?
a) Ozone is a resonance hybrid of oxygen
b) Ozone is an allotropic modification of oxygen
c) Ozone is an isomer of oxygen
d) Ozone has no relationship with oxygen

23) The oxide which cannot act as a reducing agent is
a)
b)
c)
d)

24) Iron when treated with conc. nitric acid
a) Readily reacts
b) Slowly reacts
c) Becomes passive
d) Gives ferrous nitrate

25) What is formed when HNO3 is heated?
a)
b)
c)
d) NO

26) NH3 and H2O form NH4+and OHby
a) Electrovalent bond
b) Covalent bond
c) Coordinate bond
d) None of these

27) Ammonia is bubbled through copper sulphate solution, and a deep blue solution results. The deep blue colour is due to formation of
a)
b)
c)
d) None of these

28) KO2 + CO2 ?(gas)
a)
b)
c)
d) CO

29) The test of O3 can be done by
a) Ag
b) Hg
c) Au
d) None of these

30) Of the following substances the one which does not contain oxygen is
a) Epsom salt
b) Bauxite
c) Cryolite
d) Dolomite

31) When HNO3 is heated with copper, the colour of the gas produced is yellowish-brown. The gas is
a)
b)
c) NO
d)

32) H2SO4 is very corrosive on skin. The primary reason is
a) It reacts with proteins
b) It acts as oxidising agent
c) It acts as a dehydrating agent and the absorption of water is highly exothermic
d) None

33) An element (X) forms compounds of the formula XCI3, and but does not form XCI5.Which of the following is the element X ?
a) B
b) Al
c) N
d) P

34) Which of the following is obtained when N2 reacts with calcium carbide?
a) Calcium cyanate
b) Calcium acetate
c) Calcium cyanamide
d) Calcium carbonate

35) Which of the following oxides reacts with HCI and NaOH ?
a) CaO
b) ZnO
c)
d)

36) Ozone reacts with moist iodine to form
a)
b)
c)
d)

37) Which one of the following pairs of substances will not evolve H2 gas on reaction?
a)
b) Iron and steam
c) Copper and HCI (aq)
d) Sodium and ethanol

38) Carbogen is a
a) Pure form of carbon
b)
c)
d)

39) @ Ozone is prepared by passing an electric discharge through oxygen. In this reaction
a) Energy is given out
b) Energy is absorbed
c) Oxygen is isomerized
d) Oxygen is dissociated into atoms

40) When KBr is treated with conc. H2SO4, reddish brown gas is evolved. The gas is
a)
b)
c)
d) None

41) Which is not the property of nitrogen?
a) Hydrogen Bonding
b) Catenation
c) Supporter of life
d) Low boiling point

42) Which oxide of nitrogen has nitrogen in the lowest oxidation state?
a) Nitric oxide
b) Nitrous oxide
c) Nitrogen dioxide
d) Dinitrogen tetroxide

43) If HNO3 changes into N2O, the oxidation number of N is changed by
a) 2
b) 6
c) 0
d) 4

44) Which of the following is formed by the action of water on sodium peroxide?
a)
b)
c)
d)

45) In the reaction HNO3 + P4O10 4 HPO3 + X, the product X is
a)
b)
c)
d)

46) Nitrogen atom has an atomic number of 7 and oxygen has an atomic number 8. The total number of electrons in a nitrate ion will be
a) 8
b) 16
c) 32
d) 64

47) The crystals of FeSO4 on heating gives
a)
b)
c)
d)

48) The conjugate acid of is
a)
b)
c)
d)

49) The relationship between the dissociation energy of N2 and that of N2+ is
a)
b)
c)
d)

50) On heating sodium metal in a current of dry ammonia, the compound formed is
a) Sodium amide
b) Sodium azide
c) Sodium nitride
d) Sodium hydride

51) The nitride ion in lithium nitride is composed of
a) 7 Protons + 10 electrons
b) 10 Protons + 10 electrons
c) 7 Protons + 7 electrons
d) 10 Protons + 7 electrons

52) The correct order of acidic strength is
a)
b)
c)
d)

53) The hybridization in the atomic orbitals of nitrogen in , and are
a)
b)
c)
d)

54) Ammonia can be dried by
a)
b)
c) CaO
d)

55) A deep brown gas is formed by mixing two colourless gases which are
a)
b)
c)
d)

56) Mark the oxide which is amphoteric in character:
a)
b)
c)
d) CaO

57) A metal which does not liberate H2 (g) from acids is
a) Cu
b) Fe
c) Mn
d) Zn

58) Which of the following has an odd number of electrons?
a) NO
b) CO
c)
d)

59) The bond angle in SO2 is nearly
a)
b)
c)
d)

60) The most abundant element in the earths crust (by weight) is
a) Si
b) Al
c) O
d) Fe

61) O3 is used to purify water since it
a) Is paramagnetic
b) Absorbs harmful UV radiations
c) Is reducing
d) Destroys bacteria and viruses

62) Gold is insoluble in nitric acid but dissolves in aqua regia. The enhanced solubility of gold arises from the
a)
b)
c)
d) Gold nitrate formation

63) Liquid ammonia and liquor ammonia are
a) The same
b) Different
c) Allotropes
d) None

64) Hydrazine reduces Fehling solution to
a) CuO
b)
c)
d)

65) A gas which was formerly used as an anaesthetic in dental surgery is
a) NO
b)
c)
d) All the above

66) Hydrogen has three isotopes. The radioactive isotope has the mass number
a) 3
b) 6
c) 2
d) All the above

67) Semi water gas is a mixture of
a)
b)
c)
d) None

68) An odd electron bond is not present in
a) NO
b)
c)
d) None of the above

69) Liquid oxygen is
a) Colourless
b) Pale yellow
c) Pale blue
d) Dark blue

70) Which of the following combines with Fe(II) ions to form a brown complex?
a)
b) NO
c)
d)

71) Which of the following colours is not associated with ozone?
a) Pale Blue
b) Blue
c) Purple
d) Green

72) Nitrogen can be purified from the impurities of oxides of nitrogen and ammonia by passing through
a) Ammoniacal copper sulphate
b) Conc. HCl
c) A solution of KOH
d) None

73) Hydrogen can form bonds
a) By losing an electron only
b) By gaining an electron only
c) By sharing an electron only
d) All the above

74) Hydrogen can be obtained from water
a) Only by electrolysis
b) Only by the action with active metals
c) Only by the reaction with metal hydrides
d) All the above

75) Which of the following on reaction with H2SO4, will not liberate hydrogen: Zn, Al2O3, Cu?
a)
b)
c)
d) Both Al2O3 and Cu

76) Oxygen is not evolved when
a) Potassium chlorate is heated
b) Sodium peroxide reacts with water
c) Ammonium nitrate is heated
d) All the above

77) Out of MgO, BeO, SnO, which is/are amphoteric ?
a) MgO and SnO
b) BeO and MgO
c) BeO and SnO
d) SnO alone

78) Which of the following statements are correct?
a)
b)
c)
d) All the above

79) Which of the following metals Fe, Al and Ni become passive on reacting with conc. HNO3?
a) Fe alone
b) Al and Fe
c) Ni and Al
d) All the three

80) sp2-Hybridization is found in the structures of
a)
b)
c)
d) both a and c

81) Which of the following is isoelectronic as well as having the same structure as that of N2O?
a)
b)
c)
d)

82) The molecule which has a pyramidal shape is
a)
b)
c)
d)

83) Which of the following oxides is the most acidic?
a)
b)
c)
d)

84) Orthophosphoric acid is
a) Monobasic
b) Dibasic
c) Tribasic
d) Tetrabasic

85) The number of P-O-P bonds in a cyclic metaphosphoric acid is
a) Zero
b) Two
c) Three
d) Four

86) The hybridisation of the atomic orbitals of nitrogen in NO, NO, and NH are
a)
b)
c)
d)

87) Which of the following forms of phosphorus is the most reactive?
a) Red phosphorus
b) Yellow or white phosphorus
c) Scarlet phosphorus
d) Violet phosphorus

88) Nitrogen can be obtained from air by removing
a) Oxygen
b) Hydrogen
c) Carbondioxide
d) Oxygen, CO2 , and noble gases

89) Repeated use of which of the following fertilizers would increase the acidity of the soil?
a) Urea
b) Potassium nitrate
c) Ammonium sulphate
d) Super phosphate of lime

90) An element (X) forms compounds of the formula XCl3,X2O5 and Ca3X2, but does not form XCl5. Which of the following is the element?
a) B
b) Al
c) N
d) P

91) There is very little difference in acid strengths in the series H3PO4, H3PO3 and H3PO2 because
a) Phosphorus is not a highly electronegative element
b) The hydrogens in these acids are not all bonded to phosphorus
c) Phosphorus in these acids exists in different oxidation states
d) Phosphorus oxides are less basic

92) Sodium pyrophosphate is
a)
b)
c)
d)

93) In the nitrogen family the H-M-H bond angle in the hydrides MH3 gradually becomes closer to 90° on going from N to Sb. This shows that gradually
a) The basic strength of the hydrides increases
b) Almost pure p-orbitals are used for M-H bonding
c) The bond energies of the M-H bond increases
d) The bond pairs of electrons becomes nearer to the central atom

94) Which oxide of nitrogen is a coloured gas?
a)
b) NO
c)
d)

95) Which of the following is a tetrabasic acid?
a) Orthophosphoric acid
b) Hydrophosphoric acid
c) Metaphosphoric acid
d) Pyrophosphoric acid

96) The basic character of the hydrides of VA (15) group elements decreases in the order
a)
b)
c)
d)

97) Among the trihalides of nitrogen which one is most basic?
a)
b)
c)
d)

98) Which of the following species has the highest dipole moment?
a)
b)
c)
d)

99) Group 15 of the periodic table consists of N, P, As, Sb and Bi. On passing from N to Bi, the oxides of the elements with the general formula M2O3 becomes
a) Stronger reducing agents
b) More ionic
c) More basic
d) More volatile

100) Which one of the following penta fluorides cannot be formed?
a)
b)
c)
d)


Answer :

Ans 1) d

Ans Desc 1) N2 molecule contains triple bond between N atoms having very high dissociation energy (946 kJ mol-1 ) due to which it is relatively inactive.

Ans 2) c

Ans Desc 2) Anhydrous CaCI2 is used for fast drying of neutral gases.

Ans 3) a

Ans Desc 3) 2 NH3 + 3 CuON2+3 Cu+3 H2O.

Ans 4) c

Ans Desc 4) A proton (H+) being very small in size would have a very large hydration energy.

Ans 5) c

Ans Desc 5) Ozone is diamagnetic, because it has no unpaired electron in its structure.

Ans 6) c

Ans Desc 6)

Ans 7) c

Ans Desc 7) Ozone is not an element. It is a compound of oxygen.

Ans 8) b

Ans Desc 8) CaC2 + N2 CaCN2 + C.

Ans 9) b

Ans Desc 9) At room temperature ordinary hydrogen contains 25% para and 75% ortho hydrogen.

Ans 10) b

Ans Desc 10) MgO is the most basic of all the mentioned oxides.

Ans 11) d

Ans Desc 11) 3Mg + N2 Mg3N2.

Ans 12) c

Ans Desc 12) BaO2 + H2SO4 BaSO4 + H2O2.

Ans 13) c

Ans Desc 13) BeO and SnO2 both are amphoteric.

Ans 14) c

Ans Desc 14) O3 is used for sterilising water.

Ans 15) b

Ans Desc 15)

Ans 16) c

Ans Desc 16) Due to intermolecular H-bonding, NH3 has higher b.p. than PH3.

Ans 17) c

Ans Desc 17) SO has the structure.

Ans 18) c

Ans Desc 18)

Ans 19) a

Ans Desc 19)

Ans 20) d

Ans Desc 20) SO2 + 2CuCl2 + 2H2O + H2SO4 + 2HCl.

Ans 21) d

Ans Desc 21) Both white P and red P burn in oxygen at 30oC forming trioxide and pentoxide.

Ans 22) b

Ans Desc 22) O2 and O3 are allotropes.

Ans 23) d

Ans Desc 23) In CO2, C has maximum valency of 4. It cannot be further increased, thus CO2 cannot act as a reducing agent.

Ans 24) c

Ans Desc 24)

Ans 25) c

Ans Desc 25) 4 HNO3 2 H2O + 4 NO2 + O2.

Ans 26) a

Ans Desc 26) NH3 + H2O + OH.

Ans 27) c

Ans Desc 27) CuS04+4NH3 [Cu (NH3) 4] SO4 or [Cu (NH3)4] 2+ (deep blue colour)

Ans 28) c

Ans Desc 28) 4KO2+ 2CO2 2 K2CO3 + 3 O2.

Ans 29) b

Ans Desc 29) 2 Hg + O3 Hg2O + O2 (tailing of Hg)

Ans 30) c

Ans Desc 30) Na3AIF6 is cryolite which does not contain oxygen.

Ans 31) a

Ans Desc 31) HNO3 is decomposed to NO2 which has a yellowish orange colour.

Ans 32) c

Ans Desc 32) Corrosive action is due to dehydration of skin. It has great affinity for water.

Ans 33) c

Ans Desc 33) N can form NCI3, N2O5 and Ca3N2 but not NCI5 due to non-availability of d-orbitals.

Ans 34) c

Ans Desc 34) CaC2 + N2 CaCN2 +C.

Ans 35) b

Ans Desc 35) ZnO is amphoteric, it reacts with HCI as well as NaOH.

Ans 36) a

Ans Desc 36) 5O3 + I2 + H2O 2HIO3 + 5O2.

Ans 37) c

Ans Desc 37) Cu does not react with HCI (dil.)

Ans 38) d

Ans Desc 38) A mixture of O2 (80%) and CO2 (20%) is called carbogen.

Ans 39) b

Ans Desc 39)

Ans 40) a

Ans Desc 40) 2KBr + 3H2SO4 2KHSO4 + SO2 + Br2+ 2H2O.

Ans 41) c

Ans Desc 41) N2 is not a supporter of life.

Ans 42) b

Ans Desc 42) NH4NO3 N2O + 2 H2O.

Ans 43) d

Ans Desc 43)

Ans 44) c

Ans Desc 44)

Na2O2 + 2 H2O 2 NaOH + H2O2

2H2O2 2H2O + O2.

Ans 45) b

Ans Desc 45) 4HNO3 + P4O10 4 HPO3 + 2N2O5.

Ans 46) c

Ans Desc 46) =7 + 8 x 3 + 1= 32 electrons.

Ans 47) c

Ans Desc 47) 2FeSO4. 7H2O Fe2O3+ SO2 + SO3 + 7H2O.

SO3 + H2OH2SO4

Ans 48) d

Ans Desc 48)

Ans 49) d

Ans Desc 49) N2 (bond order = 3) has greater dissociation energy than (bond order = 2.5)

Ans 50) a

Ans Desc 50) 2 Na + 2 NH3 2 NaNH2 + H2.

Ans 51) a

Ans Desc 51) N3- (nitride ion) contains 7 protons and 10 electrons.

Ans 52) a

Ans Desc 52) Acidic strength increases along a period.

Ans 53) b

Ans Desc 53) Hybridization of N in is sp (linear) , in is sp2 (planar triangular) and in is sp3 (tetrahedral)

Ans 54) c

Ans Desc 54) NH3 can be dried using CaO as all other reagents react with it.

Ans 55) c

Ans Desc 55) 2 NO (colourless) + O2 (colourless) 2 NO2 (reddish brown)

Ans 56) c

Ans Desc 56) SnO2 is amphoteric, which reacts with acids as well as alkalies. CaO is basic while CO2 and SiO2 are acidic.

Ans 57) a

Ans Desc 57) Cu being less electropositive than H cannot liberate hydrogen from acids.

Ans 58) a

Ans Desc 58) Total number of electrons in NO are 7 + 8 = 15, in CO are 6 + 8 = 14, in N2 are 7 + 7 = 14 and in CO2 are 6 + 16 = 22. Thus NO has an odd number of electrons (15)

Ans 59) a

Ans Desc 59) Because S in SO2 is sp2 hybridised.

Ans 60) c

Ans Desc 60)

Ans 61) d

Ans Desc 61) Ozone is used to purify (sterilise) water since it destroys bacteria and viruses.

Ans 62) c

Ans Desc 62)

Aqua regia (1 : 3 ratio of conc. HNO3 and conc. HCI) produces nascent chlorine which reacts with Au to form AuCI3. AuCI3 in excess of HCI forms a soluble chloro complex

HNO3+3HCI 2H2O+NOCI+2 | CI|.

Au + 3 | Cl | AuCI3.

AuCI3 + HCI H AuCI4 (aurochloric acid or chloro auric acid).

Ans 63) b

Ans Desc 63) Liquid ammonia is liquified NH3 gas under pressure while liquor ammonia is concentrated solution of NH3 gas in water.

Ans 64) b

Ans Desc 64)
Hydrazine   From Fehling
solution

Ans 65) c

Ans Desc 65) When is inhaled in moderate quantity it affects the central nervous system . Hence it is used as an anaesthetic.

Ans 66) a

Ans Desc 66) Radioactive isotope of hydrogen is (tritium)

Ans 67) c

Ans Desc 67) A mixture of CO + H2 + N2 is called semi water gas.

Ans 68) d

Ans Desc 68) A bond formed by three electrons is called an odd electron bond.

Ans 69) c

Ans Desc 69) Liquid oxygen has a pale blue colour.

Ans 70) b

Ans Desc 70) FeSO4+ NO FeSO4.NO (Nitrosoferrous sulphate).

Ans 71) d

Ans Desc 71) Ozone in the gaseous state is pale blue, dark blue in the liquid state and purple in the solid state.

Ans 72) c

Ans Desc 72) Oxides of nitrogen are acidic which are dissolved in a solution of KOH.

Ans 73) d

Ans Desc 73) H can form bonds by all the three ways as mentioned.

Ans 74) d

Ans Desc 74) H2 can be prepared from water by all the three ways as mentioned.

Ans 75) d

Ans Desc 75) Al2O3 + 2 NaOH 2 NaAIO2 + H2O

Cu+2 H2SO4 (conc.) CuSO4+SO2+2 H2O

Ans 76) c

Ans Desc 76) NH4NO3 N2O + 2 H2O

Ans 77) c

Ans Desc 77) BeO and SnO both are amphoteric oxides.

Ans 78) c

Ans Desc 78) NO+O (oxidising agent).
N2O5 + 2 NaOH2 NaNO3 + H2O.

Ans 79) d

Ans Desc 79) Fe, Al and Ni become passive on reacting with conc. HNO3.

Ans 80) d

Ans Desc 80) O3 and NO3 contain sp2-hybridized O and N atoms respectively.

Ans 81) d

Ans Desc 81) Like CO2, N2O is a linear molecule and isoelectronic with CO2 with 22 electrons each. CO2 = 6 + 16 = 22 = N2O = 14 + 8 = 22.

Ans 82) a

Ans Desc 82) PCI3 is pyramidal in shape (sp3 hybridisation).

Ans 83) a

Ans Desc 83) Acidic strength decreases on moving down a group.

Ans 84) c

Ans Desc 84) Orthophosphoric acid H3PO4 is tribasic.

Ans 85) c

Ans Desc 85) Metaphosphoric acid is HPO3

Cyclic metaphosphoric acid has the structure shown below. Thus there are three P-O-P bonds

Ans 86) b

Ans Desc 86) No. of hybrid orbitals = Total no. of sigma bonds + lone pair of electrons. The no. of sigma bonds in NO, NO and NH are 2,3 and 4 respectively. So the hybridisation is sp, sp2 and sp3 respectively.

Ans 87) b

Ans Desc 87) White or yellow phosphorus is the most reactive form of phosphorus.

Ans 88) d

Ans Desc 88) Air mainly contains N2 and O2 along with some CO2.

Ans 89) c

Ans Desc 89) In soil ammonium sulphate undergoes hydrolysis to give H2SO4 .

Ans 90) c

Ans Desc 90) N forms NCl3,N2O5 and Ca3N2. Nitrogen, which has no empty d-orbitals, cannot extend its covalency by more than three and hence does not form NCl5.Due to its small size and high electronegativity it can accept 3 electrons to form N3- ion (Ca3N2).

Ans 91) a

Ans Desc 91) There is little difference in the strength of these acids because phosphorus is not a highly electronegative element.

Ans 92) c

Ans Desc 92)

Ans 93) b

Ans Desc 93) The hybrids have a pyramidal or tetrahedral shape with a lone pair of electrons in one of the orbitals. The H-M-H bond angle is less than the original 109°28 tetrahedral bond angle (H-N-H in NH3 is 106°45) because of greater repulsion between a lone pair and a bond pair than between two bond pairs of electrons. Because the electronegativity of M decreases from N to Bi, the bond pair lies farther away from the central atom, and the lone pair causes greater distortion of the bond angle. Thus the H-P-H bond in PH3 is 94, while in AsH3 and SbH3 it is about 91.8°, and 91.3° respectively (closer to 90°). This suggests that the orbitals used for bonding are closer to pure p-orbitals.

Ans 94) d

Ans Desc 94) NO2 is a reddish brown gas.

Ans 95) d

Ans Desc 95)

Pyrophosphoric acid, H4P2O7 is tetrabasic acid.

Ans 96) c

Ans Desc 96) The availability of electrons on an atom decreases down a group because of increase in size. Hence the basicity of these hydrides decreases from NH3 to SbH3 due to the increase in the size of the atom from N to Sb.

Ans 97) c

Ans Desc 97) NI3 is most basic.

Ans 98) a

Ans Desc 98) The dipole moment decreases down the group as NH3 > PH3 > AsH3 > SbH3.

Ans 99) c

Ans Desc 99) Because the availability of electrons decreases down the group.

Ans 100) d

Ans Desc 100) Due to the maximum inert pair effect in Bi, BiF5 does not exist.

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