CHEMICAL BONDING AND MOLECULAR STRUCTURE – 4

1)
a) Solution of a solid in a liquid
b) Solution of a liquid in a solid
c) Salt only and cannot be called a solution
d) Co-ordination compound of copper with water molecules as the ligands

2) The solubility of a substance is defined as the amount of solute in grams
a) Present in 100 g of the saturated solution
b) Dissolved in 100 g of the solvent to get a saturated solution
c) Dissolved in 100 ml of the solvent to get a saturated solution
d) Present in 1 litre of the saturated solution

3) Which of the following is incorrect?
a) Mass of the gas dissolved is directly proportional to its pressure
b) Mass of the gas dissolved is inversely proportional to temperature
c) A soda-water bottle contains oxygen gas dissolved under pressure
d) Permanent gases are less soluble than temporary gases

4) In liquid which of the following has maximum solubility?
a)
b)
c)
d)

5) Iodine is more soluble in alcohol than in carbon tetrachloride because
a) Iodine and alcohol both are non-polar
b)
c) The dissolution of iodine in alcohol is exothermic whereas it is endothermic in CCl4
d) The dissolution of both is endothermic but the heat of dissolution in alcohol is less than in CCl4

6) A solid dissolves in water if the
a) Lattice energy is greater than the hydration energy
b) Lattice energy is less than the hydration energy
c) Lattice energy is equal to the hydration energy
d) Dissolution is exothermic

7) The solubility of a gas in a liquid increases with
a) increase of pressure and increase of temperature
b) decrease of pressure and increase of temperature
c) increase of pressure and decrease of temperature
d) decrease of pressure and decrease of temperature

8) You are given 100 cc of to extract iodine from 200 cc of its aqueous solution. To extract the maximum amount of iodine, which one of the following processes would you adopt?
a)
b)
c) The use of 10 cc of CCl4 ten times
d)

9) Which of the following represents a metastable system?
a) A dilute solution
b) An unsaturated solution
c) A saturated solution
d) A supersaturated solution

10) The solubility curve of in water with temperature is given. The conclusion is that the

              
a) Solution process is exothermic
b)
c)
d) Solution process is endothermic

11) The most convenient way of expressing concentration is
a) Normality
b) Molarity
c) Molality
d) Mole fraction

12) The sum of mole fractions of A, B and C in a solution containing 0.1 mole each of A, B and C is:
a) 0.1
b) 0.3
c) 1.0
d) 1/3

13) Which of the following is T shaped?
a) ICl
b)
c)
d)

14) The geometry of XeF2 molecule is
a) Linear
b) Triangular planar
c) Square planar
d) Trigonal bipyramidal

15) The hybridization of Xe in XeF2 is
a)
b)
c)
d)

16) The structure of XeF4 is
a) Tetrahedral
b) Square planar
c) Linear
d) Octahedral

17) The hybridization of Xe in XeF4 is
a)
b)
c)
d)

18) Xenon reacts directly with
a)
b)
c)
d)

19) The number of lone pairs of electrons on the Xe atom in XeF4 is
a) Three
b) One
c) Two
d) None

20) In the XeF4 molecule, the two lone pairs of electrons on Xe atom occupy which of the following positions on the square planar structure ?
a) Two adjacent corners on the planar square
b) Two diagonally opposite corners on the planar square
c) One corner of the planar square and one trans position
d) Two trans positions

21) The hybridization of Xe in XeF6 is
a)
b)
c)
d)

22) The geometry of XeF6 molecule is
a) Tetrahedral
b) Pentagonal bipyramid
c) Octahedral
d) Square planar

23) Which of the following structures is most likely for XeOF4 ?
a) Tetrahedral
b) Square pyramidal
c) Square planar
d) Octahedral

24) Noble gases do not react with other elements because

a) They are monoatomic
b) The sizes of their atoms are very small
c) They are not found in abundance
d) They have completely paired closed electron shells

25) The spectrum of He is expected to be similar to that of
a)
b)
c) H
d) Na

26) The noble gas which shows abnormal behaviour in the liquid state is
a) Ar
b) Xe
c) He
d) Kr

27) When the mineral cleveite is heated, it gives off  the inert gas
a) Helium
b) Xenon
c) Radon
d) Argon

28) The noble gas used for the treatment of cancer is
a) Helium
b) Argon
c) Radon
d) Krypton

29) The melting points and boiling points of noble gases show
a) A very little difference
b) A very large difference
c) No difference at all
d) None of the above

30) The heats of vaporization of noble gases vary in the order
a) He> Ne> Ar> Kr> Xe> Rn
b) He < Ne < Ar < Kr < Xe < Rn
c) Xe < Kr < Ne < He < Rn < Ar
d)

31) Among the following, the most volatile of all liquids is
a) Ne
b) Ar
c) Xe
d) He

32) Which of the following can be liquefied most  easily ?
a) He
b) Ne
c) Xe
d) Kr

33) Which of the following is more soluble in water?
a)
b)
c) Ar
d) He

34) Noble gases exist only in the monoatomic state.This is due to
a) the non availability of unpaired electrons
b) Their high ionization energy
c) Their very large sizes
d) Their almost zero electron affinity

35) The gases which cannot diffuse through glass, rubber and PVC are
a) Xe
b) Kr
c) Ar
d) All the above

36) The noble gas which can diffuse through rubber and glass easily is
a) Xe
b) Ne
c) Ar
d) He

37) When an electric discharge is passed through neon gas at low pressure, the colour of the  glow obtained is

a) Brilliant orange red
b) Blue
c) Green
d) White

38) The noble gas showing the least thermal conductivity at 273 K and atmospheric pressure is
a) He
b) Ne
c) Ar
d) Xe

39) Clathrates are
a) Non-stochiometric compounds
b) Complex compounds
c) Interstitial compounds
d) Normal salts

40) The last orbit of argon would have — electrons
a) 8
b) 18
c) 2
d) 6

41) The least chemical activity is shown by
a)
b)
c) Ar
d)

42) The electronic configuration of neon is
a)
b)
c)
d)

43) If one litre of air is passed repeatedly over heated copper and magnesium till no further reduction in volume takes place, the volume finally obtained would be approximately.
a) 800ml
b) 200ml
c) 10ml
d) Zero

44) Which of the following outer electronic configurations represents argon ?
a)
b)
c)
d)

45) Which of the following is monoatomic ?
a) Oxygen
b) Neon
c) Fluorine
d) Nitrogen

46) The noble gas forming the maximum number of compounds is
a) Ne
b) Xe
c) Kr
d) Rn

47) The noble gases which form clathrates are
a) Ar
b) Kr
c) Xe
d) All of these

48) Noble gases do not react with other elements because
a) They are mono-atomic
b) They are found in abundance
c) The size of their atoms is very small
d) They have completely paired up and stable electron shells

49) Which of the following rare gases is the most abundant in air ?
a) He
b) Ne
c) Ar
d) Kr

50) Which of the following fluorides of xenon is impossible ?
a)
b)
c)
d)

51) The XeF2 molecule is
a) Linear
b) Trigonal planar
c) Pyramidal
d) Square planar

52) Which one of the following noble gases is least polarizable ?
a) He
b) Ne
c) Kr
d) Xe

53) The following has zero valency
a) Na
b) Be
c) Al
d) Kr

54) The atomic radii of fluorine and neon in angstrom units are respectively given by
a) 0.72, 1.60
b) 1.60, 1.60
c) 0.72, 0.72
d) None of these values

55) Which of the following statements is not true about noble gases ?
a) Their ionization energies are very high
b) Their electron affinities are nearly zero
c) They do not form any chemical compounds
d) They are not easily liquefied

56) A helium-oxygen mixture is used by deep sea divers in preference to a nitrogen-oxygen mixture because

a) Helium is much less soluble in blood than nitrogen
b) Nitrogen is much less soluble in blood than helium
c) Nitrogen & oxygen react to give poisonous nitric oxide
d) Nitrogen is highly soluble in water

57) The forces acting between noble gas atoms are
a) van der Waals forces
b) lon-dipole forces
c) London dispersion forces
d) Magnetic forces

58) The percentage of Ar in air is about
a) 1%
b) 2%
c) 3%
d) 4%

59) The structure of XeF6 is
a) Distorted octahedral
b) Pyramidal
c) Tetrahedral
d) None of the above

60) Which of the following statements about noble   gases is false ?
a) They are used to provide inert atmosphere in many chemical reactions
b) They are only sparingly soluble in water
c) They form diatomic molecules
d) Some of them are used to fill discharge tubes used for advertising signs

61) Among noble gases (from He to Xe) only xenon reacts with fluorine to form stable xenon fluorides because xenon
a) Has the largest size
b) Has the lowest ionization enthalpy
c) Has the highest heat of vaporization
d) Is the most readily available noble gas

62) The oxidation number of Xe in XeOF2 is
a) 0
b) 2
c) 4
d) 3

63) Argon was discovered by
a) Ramsay
b) Rayleigh
c) Rutherford
d) Both (a) and (b)

64) If the ionization potential for the hydrogen atom is 13.6 eV, then the ionization potential for He+ will be :
a) 54-4eV
b) 68eV
c) 13-6eV
d) 24-5eV

65) Which of the following noble gases is not present in the atmosphere ?
a) He
b) Ne
c) Ar
d) Rn

66) The gases which are not used by deep sea divers for artificial respiration are
a)
b) Xe
c) Kr
d) Both b and c

67) Which of the following statements is not correct for a noble gas ?
a) Ar is used in electric bulbs
b) Kr is obtained during radioactive disintegration
c) Half life of Rn is only 3-8 days
d) He is used in producing very low temperatures

68) In the following four elements, the ionization potential of which one is the highest ?
a) Oxygen
b) Argon
c) Barium
d) Cesium

69) The noble gas which was discovered first in the sun and then on the earth is
a) Argon
b) Xenon
c) Neon
d) Helium

70) XeF4 involves which hybridisation
a) sp
b)
c)
d)

71) In the clathrates of xenon with water, the nature of the  bonding between xenon and water molecule is
a) Covalent
b) Hydrogen bonding
c) Co-ordinate
d) Dipole-induced dipole interaction

72) The last member of the family of inert gases is
a) Argon
b) Radon
c) Xenon
d) Neon

73) The coloured discharge tubes for an advertisement mainly contain
a) Xenon
b) Helium
c) Neon
d) Argon

74) XeF4 on partial hydrolysis produces
a)
b)
c)
d)

75)

Which of the following is the correct sequence of the noble gases in their group in the periodic table ?

a) Ar, He, Kr, Ne, Rn, Xe
b) He, Ar, Ne, Kr, Xe, Rn
c) He, Ne, Kr, Ar, Xe, Rn
d) He, Ne, Ar, Kr, Xe, Rn

76) The value of the ionization potential for inert gases is
a) Zero
b) Low
c) High
d) Negative

77) The elements which occupy the peaks of ionization energy curve are
a) Na, K, Rb, Cs
b) Na, Mg, Cl, I
c) Cl, Br, I, F
d) He, Ne, Ar, Kr

78) Which of the following cannot be formed ?
a)
b)
c) He
d)

79) The element which has not yet been reacted with F2 is
a) Ar
b) Xe
c) Kr
d) Rn

80) The molecular shapes of SF4, CF4 and XeF4 are
a) The same, with 2, 0 and 1 lone pairs of electrons respectively
b) The same, with 1, 1 and 1 lone pairs of electrons respectively
c) Different, with 0, 1 and 2 lone pairs of electrons respectively
d) Different, with 1, 0 and 2 lone pairs of electrons respectively.

81) In which of the following groups should helium be placed for all its properties to be satisfied ?
a) With alkali metals
b) With the halogens
c) With inert gases
d) None of these

82) The shape of XeOF4 is
a) Octahedral
b) Square pyramidal
c) Pyramidal
d) T-shaped

83) The most abundant inert gas in the atmosphere is
a) He
b) Ne
c) Ar
d) Kr

84) The lowest boiling point of helium is due to its
a) Inertness
b) Gaseous nature
c) High polarisability
d) Weak van der Waals forces between atoms

85) The total number of electrons surrounding Kr in KrF2 is
a) 4
b) 6
c) 2
d) 10

86) Which of the following is an explosive compound ?
a)
b)
c)
d)

87) The structure of the ion is
a) Trigonal bipyramidal
b) Square pyramidal
c) Octahedral
d) Pentagonal

88) The D3 line observed in the yellow region of the sun’s spectrum is due to
a) Na
b) Ne
c) Kr
d) He

89) Which of these is a degenerate gas?
a) He
b) He I
c) He II
d)

90) XeO3 is obtained by complete hydrolysis of
a)
b)
c)
d) All the above

91) Which of the following is used as an anaesthetic due to the formation of aqueous clathrates in physiologically strategic spots ?
a) Rn
b) Xe
c)
d)

92) Which of the following is used in very low temperature thermometers ?
a) He
b) Ne
c)
d)

93) In analogy to O+ [PtF6] a compound N+ [PtF6] will not be formed because
a)
b)
c)
d) None of these

94) Which of the following compounds cannot be stored in glass vessels ?
a)
b)
c)
d)

95) Which of the following light is effective in the formation of chlorophyll ?
a) Sodium lamp
b) Neon lamp
c) Mercury lamp
d) Argon lamp

96) Which of the following does not exist ?
a)
b)
c)
d)

97) The inert gases can be isolated and separated by
a) Electrolysis of their compounds
b) Fractional distillation of liquid air
c) Absorption and desorption on charcoal
d) Both b and c

98) Which of the following react with fluorine ?
a) Kr
b) Xe
c) Ar
d) Both a and b

99) Which of the following noble gases are found in the atmosphere ?
a) Ne
b) Kr
c) Ar
d) All the above

100) Noble gases occur in
a) Ores
b) the atmosphere
c) Natural gas
d) All the above

Ans 1) b

Ans Desc 1) Liquid is uniformly mixed into solid .

Ans 2) b

Ans Desc 2) Solubility of a substance is defined as the amount of solute in grams dissolved in 100 g
of the solvent to get a saturated solution.

Ans 3) c

Ans Desc 3) A soda-water bottle contains gas dissolved under pressure.

Ans 4) b

Ans Desc 4) being a liquid has more solubility than (NaCl being ionic).

Ans 5) d

Ans Desc 5) In the endothermic process of dissolution, the energy factor opposes the dissolution. The less the heat of dissolution i.e. the less the opposing factor, the greater is the solubility.

Ans 6) b

Ans Desc 6) A solid dissolves in water if the lattice energy is less than the hydration energy.

Ans 7) c

Ans Desc 7) Solubility of a gas in a liquid increases with increase of pressure and decrease of temperature.

Ans 8) c

Ans Desc 8) The greater the no. of instalments, the greater the extraction.

Ans 9) d

Ans Desc 9) A supersaturated solution is metastable because on slight disturbance, the solid separates out.

Ans 10) c

Ans Desc 10) Solubility increases with temp. upto and then decreases. So the process is endothermic upto and exothermic thereafter.

Ans 11) b

Ans Desc 11) The most convenient way of expressing concentration is molarity.

Ans 12) c

Ans Desc 12) The sum of mole fractions of all the components = 1

Ans 13) b

Ans Desc 13) ClF3 has sp3d hybridisation and is T-shaped.

Ans 14) d

Ans Desc 14) The geometry of a molecule is given by the type of hybridization of the central atom (sp3 d) which includes the positions of both atoms as well as lone pairs of electrons whereas the shape or  structure of a molecule implies only the position of atoms (linear).

Ans 15) c

Ans Desc 15) In order to get only two unpaired electrons, one of the 5p electrons of Xe is promoted to a higher energy 5d orbital. Then 5s, three 5p and one 5d atomic orbitals hybridize to give five sp3 d  hybridized orbitals, two of which are singly occupied and the other three doubly occupied.  The geometry of the molecule is trigonal bipyramid and the shape is linear.

Ans 16) b

Ans Desc 16) Xe in XeF4 involves sp3 d2 hybridization giving an octahedral geometry but the two trans positions are occupied by lone pairs and the shape or structure of the molecule is square planar.

Ans 17) b

Ans Desc 17) Xe in XeF4 involves sp3 d2 hybridization giving an octahedral geometry but the two trans positions are occupied by lone pairs and the shape or structure of the molecule is square planar.

Ans 18) a

Ans Desc 18) Xenon reacts directly with F2 under different conditions to give its fluorides.

Ans 19) c

Ans Desc 19) Xe in XeF4 involves sp3 d2 hybridization giving an octahedral geometry but two trans positions are occupied by lone pairs and shape or structure of the molecule is square planar.

Ans 20) d

Ans Desc 20) Xe in XeF4 involves sp3 d2 hybridization giving an octahedral geometry but two trans positions are occupied by lone pairs and shape or structure of the molecule is square planar.

Ans 21) c

Ans Desc 21) It is assumed that three electrons from the 5 p sub level of Xe are promoted to 5 d sub level.  Then 5 s, three 5 p and three 5 d orbitals hybridize to produce seven sp3 d3 hybrid orbitals out of which six are singly occupied which form bonds with six fluorine atoms and the seventh orbital contains a lone pair in trans position.

Ans 22) b

Ans Desc 22)

sp3 d3 hybridization as discussed above will give a pentagonal bipyramid geometry with one  trans position occupied by a lone pair and the shape of the molecule will be distorted octahedral.

Ans 23) b

Ans Desc 23) Here three 5 p electrons of Xe are promoted to the 5 d sub level. Then 5s, three 5 p and two 5 d orbitals hybridize to give six sp3 d2hybrid orbitals in an octahedral geometry out of which five  are singly occupied which form sigma bonds with four F and one 0 atoms. The unhybridized  single electron in a d-orbital is used for bond formation to oxygen atom. The sixth hybrid orbital is occupied by a lone pair in trans position giving a square pyramid structure.

Ans 24) d

Ans Desc 24) Other elements due to their lower electronegativity (than those of F and O) can not unpair and remove (oxidise) the electron from completely paired np closed electron shells  (ns2 np6) of noble gases and thus the latter do not react to form compounds.

Ans 25) b

Ans Desc 25) Both He (1 s2) and Li+ (1 s2) have two electrons (dielectron species) and thus their spectrum would be similar.

Ans 26) c

Ans Desc 26) Gaseous He on cooling below 2.2 K, at one atmosphere gives a new form of helium,He II which is an extraordinary conductor of heat (about 600 times more than that of copper). It is frictionless and behaves like a super liquid with nearly zero viscosity. This liquid flows uphill and has the properties of a degenerate gas.

Ans 27) a

Ans Desc 27) Cleveite (a uranium mineral) on heating gives off Helium gas because helium formed by the disintegration of U – 238 was entrapped within it.

Ans 28) c

Ans Desc 28) Radon is radioactive with a half life period of 3.8 days and is used for the treatment of cancer.

Ans 29) a

Ans Desc 29) The m.p. and b.p. of noble gases show a very little difference in their values which shows that solids change to vapours easily.

Ans 30) b

Ans Desc 30) The heats of vaporization increase from He to Rn as the size increases.

Ans 31) d

Ans Desc 31) Since the heat of vaporization of He is the lowest, it is most difficult to liquefy it. Hence He is the most volatile of all liquids.

Ans 32) c

Ans Desc 32) Since the van der Waals forces of attraction increase from He to Xe as the size of their atoms increases, the ease of liquefaction increases from He to Xe.

Ans 33) c

Ans Desc 33) Ar is more soluble in water than O2 and N2 and also He.

Ans 34) a

Ans Desc 34) All noble gases are monoatomic as they do not have unpaired electrons for sharing with other atoms to form diatomic molecules.

Ans 35) d

Ans Desc 35) Only He due to its small size can diffuse through glass, rubber and PVC. All other gases cannot diffuse.

Ans 36) d

Ans Desc 36) Helium because of its very small size can diffuse through rubber, glass, PVC etc. easily.

Ans 37) a

Ans Desc 37) A brilliant orange red glow is obtained when an electric discharge is passed through neon gas at low pressure.

Ans 38) d

Ans Desc 38) The thermal conductivity of noble gases at 273 K and atmospheric pressure decreases with increasing atomic size of the gas from He to Xe.

Ans 39) a

Ans Desc 39) Clathrates are non-stoichiometric compounds where the ratio of guest and host molecules does not correspond to the ideal chemical formulae.

Ans 40) a

Ans Desc 40) The last orbit (valence shell) of noble gases contains 8 electrons distributed as ns2 np6.

Ans 41) c

Ans Desc 41) Out of all the known compounds, the least chemical activity is shown by noble gases.

Ans 42) c

Ans Desc 42) Neon is in the second period. So its electronic configuration is 1 s2 2 s2 2 p6.

Ans 43) c

Ans Desc 43) Noble gases constitute about 1 % of the total volume of air. The remaining 99%  volume  in mainly due
to oxygen and nitrogen. When 1 litre (1000 ml) of air is passed over   heated copper, oxygen is consumed and on further passing over magnesium, nitrogen  is consumed according to the equations :
2 Cu + O2 ® 2 CuO
3 Mg + N2 ® Mg3N2
In this way about 990 ml of air is consumed. The remaining volume of about 10 ml is due to mainly Ar and other noble gases.

Ans 44) b

Ans Desc 44) Except He, all the other noble gases have ns2 np6 outer electronic configuration.

Ans 45) b

Ans Desc 45) Noble gases are monoatomic.

Ans 46) b

Ans Desc 46) Rn having the lowest ionization energy is radioactive and its longest lived isotope has a  half life period of only 3.8 days. Therefore, very little is known about its ability to  form chemical compounds. Thus, the next element in order of lower ionization energy is  Xe which forms the largest number of compounds as compared to any other noble gas.

Ans 47) d

Ans Desc 47)

He due to its very small size does not form clathrates whereas other noble gases form such compounds easily.

Ans 48) d

Ans Desc 48)

Ans 49) c

Ans Desc 49) Ar is most abundant (0.934% by volume) in air.

Ans 50) b

Ans Desc 50) As no odd oxidation state of xenon is formed, it cannot form XeF3.

Ans 51) a

Ans Desc 51)

In order to get only two unpaired electrons, one of the 5p electrons of Xe is promoted to a higher energy 5d orbital. Then 5s, three 5p and one 5d atomic orbitals hybridize to give five sp3 d hybridized orbitals, two of which are singly occupied and the other three are doubly occupied.  The geometry of the molecule is trigonal bipyramidal and the shape is linear.

Ans 52) a

Ans Desc 52) Since the size of helium is smallest, its electron cloud is very tightly held and thus its polarizability is minimum.

Ans 53) d

Ans Desc 53) Kr because of its chemical inertness shows zero valency.

Ans 54) a

Ans Desc 54)

The atomic radius of fluorine is less than that of the next element, noble gas (neon) in which case only the van der Waals radius is considered which is larger than the covalent radius.

Ans 55) c

Ans Desc 55) Noble gases especially Kr and Xe form chemical compounds. So the statement that no any chemical compound is formed by noble gases is not true.

Ans 56) a

Ans Desc 56) He-O2 (80% : 20%) mixture is used by deep sea divers for artificial respiration. Because of the low inter-molecular forces in He, it is much less soluble in aqueous solutions (as compared to N2) such as blood  and does not cause “caisson sickness” or “bends” by bubbling out of blood when the worker moves from high pressure (while in deep sea) to atmospheric pressure.

Ans 57) a

Ans Desc 57) Atoms of noble gases are held together by weak van der Waals forces of attraction.

Ans 58) a

Ans Desc 58) The percentage of Ar in air is about 1% (exact value is 0-934%).

Ans 59) a

Ans Desc 59) When one transposition is occupied by a lone pair the shape of the molecule will be distorted octahedral.

Ans 60) c

Ans Desc 60) Noble gases do not form diatomic molecules as no unpaired electron is available.

Ans 61) b

Ans Desc 61) Only Xe reacts with F2 because it has the lowest  ionization enthalpy (energy).

Ans 62) c

Ans Desc 62) Oxidation number of Xe in XeOF2

Ans 63) d

Ans Desc 63) Rayleigh in collaboration with Ramsay discovered argon in 1894.

Ans 64) a

Ans Desc 64) The ionization energy of any hydrogen like species (having one electron only) is given by the  equation
I.E  =  or
Since the atomic number of H is 1 and that of He is 2, therefore, the I.E. of He+ is four times(22) the I.E.
of H      i.e = 13 – 6 x 4 = 54.4eV.

Ans 65) d

Ans Desc 65) Radon is radioactive and is prepared by a disintegration reaction of radium. It does not occur in air.

Ans 66) d

Ans Desc 66) Only He and O2 (80% : 20% ratio) mixture is used by divers for respiration.

Ans 67) b

Ans Desc 67) Kr is not radioactive and is not prepared during radioactive disintegration.

Ans 68) b

Ans Desc 68) The ionization potential of noble gases is the highest due to the closed shell electronic configuration.

Ans 69) d

Ans Desc 69) Helium was first discovered in the sun and then on the earth by heating cleveite ore.

Ans 70) d

Ans Desc 70)

Ans 71) d

Ans Desc 71) In the clathrate of Xe with water, the nature of the bonding between Xe and H2O is a dipole induced dipole interaction.

Ans 72) b

Ans Desc 72) Radon (Rn) is the last member of the noble gas family.

Ans 73) c

Ans Desc 73)

Neon gives brilliant orange red glow in discharge tubes and is widely used for advertisement purposes.

Ans 74) b

Ans Desc 74) XeF4 on partial hydrolysis produces XeOF2 as shown below
XeF4 + H2O ——> XeOF2 + 2 HF

Ans 75) d

Ans Desc 75) The correct sequence of the noble gas members in their group 18 is He, Ne, Ar, Kr, Xe, Rn from top to bottom.

Ans 76) c

Ans Desc 76) The value of ionization potential for inert gases is high due to their stable closed shell electronic configuration.

Ans 77) d

Ans Desc 77) The peaks represent the highest values. Since noble gases have the highest ionization energy values in their respective periods, these occupy peak positions in the ionization energy curve.

Ans 78) d

Ans Desc 78)

Ans 79) a

Ans Desc 79) Ar does not react with F2 due to its high ionization energy.

Ans 80) d

Ans Desc 80)

Molecular shapes of SF4 (see-saw), CF4 (tetrahedral) and XeF4 (square planar) are different with 1, 0 and 2 lone pairs of electrons respectively.

Ans 81) c

Ans Desc 81) When helium is placed in the group of inert gases, all its properties are satisfied.

Ans 82) b

Ans Desc 82) Shape of XeOF4 is square pyramidal where Xe is sp3d2 hybridized with one lone pair on one of the trans position.

Ans 83) c

Ans Desc 83) The most abundant inert gas in the atmosphere is Ar.

Ans 84) d

Ans Desc 84) Helium has the lowest boiling point due to weak van der Waals forces between its atoms.

Ans 85) d

Ans Desc 85) In KrF2, Kr involves sp3 d hybridization with three lone pairs and two bond pairs surrounding Kr giving a total number of 10 electrons.

Ans 86) d

Ans Desc 86) XeO3 is an explosive compound when dry and its explosion power is 22 times more than TNT.

Ans 87) b

Ans Desc 87)

In XeF5+,the Xe atom has only seven electrons i.e.,  5 s2 5 p5. Here two 5 p electrons are promoted to the 5 d sub level. Then 5 s, three 5 p and   two 5 d orbitals hybridize to give six sp3 d2 hybrid orbitals in an octahedral geometry.  Out of these, five orbitals are singly occupied which form sigma bonds with five F   atoms. The sixth hybrid orbital is occupied by a lone pair in trans position giving a  square pyramid structure.

Ans 88) d

Ans Desc 88) Frankland and Lockyer pointed out that the new D3 line observed in the yellow region of the suns spectrum observed by Jansen in 1868 was due to a new element which they named  Helium. It was the first noble gas to be discovered.The two known lines Dand D2  were of sodium . 

Ans 89) c

Ans Desc 89) He II is a liquid form of helium which is obtained on cooling gaseous He to 2.2 K at one atmosphere pressure. It is able to flow uphill like a gas and thus has the properties of a degenerate gas.

Ans 90) d

Ans Desc 90) Complete hydrolysis of XeF4, XeF6, XeOF4 and XeO2F2 give XeO3.
6XeF4 + 12H20® 4 Xe + 2 Xe03 + 24 HF + 3 O2
XeF6 + 3 H2O ® XeO3 + 6 HF
XeOF4 + 2 H2O ® XeO3 + 4 HF
XeO2F2 + H2O ® XeO3 + 2 HF

Ans 91) b

Ans Desc 91) It is thought that the anaesthetic action of xenon is due to aqueous clathrate formation in physiologically strategic spots. When the anaesthetic supply is stopped, the clathrate equilibrium is destroyed, the clathrate decomposes and the consciousness returns.

Ans 92) a

Ans Desc 92) Liquid helium is used in very low temperature thermometers.

Ans 93) d

Ans Desc 93)

The ionization energy of N2 gas (1503 kJ mol -1) is higher than that of O2 gas (1175 kJ mol-1) and it cannot lose its electron so easily as O2 does in forming O2+ [PtF6] compound.

Ans 94) d

Ans Desc 94) XeF6 cannot be stored in glass vessels because it reacts with SiO2 of the glass to give highly explosive Xe03.
                   
2 XeF6 + 3 SiO2 ——> 2 XeO3 + 3 SiF4

Ans 95) b

Ans Desc 95) When an electric discharge is passed through neon gas in a tube at low pressure, an intense orange red light is produced which is effective in the formation of chlorophyll and is used in greenhouses.

Ans 96) b

Ans Desc 96)

KrF2 is a F donor and forms complexes with F~  acceptors where only cationic species of Kr  will be present.

Ans 97) d

Ans Desc 97) Inert gases can be isolated and separated by both fractional distillation of liquid air as well as adsorption and desorption of noble gases on charcoal.

Ans 98) d

Ans Desc 98) Only Kr and Xe form compounds with F2.

Ans 99) d

Ans Desc 99) Neon, argon and krypton out of these four gases are found in the atmosphere.

Ans 100) d

Ans Desc 100) Noble gases occur in ores such as cleveite, in the atmosphere and in natural gas.

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