CBSE Guess > Papers > Important Questions > Class XII > 2008 > Chemistry > Chemistry By Mr. S.Vasu

Chemistry

Q. 45. SF₆ is known while SH₆ is unknown.

Q. 46. H₂O is a liquid while H₂S is a gas.

Q. 47. MnO is basic while Mn₂O₇ is acidic.

Q. 48. O₃ is thermo dynamically unstable than O₂ (or) . O₃ in higher concentration is explosive.

Q. 49. NO gas depletes ozone layer.

Q. 50. Sulphur in vapour state is paramagnetic.

Q. 51. HCl and HNO₃ are prepared by reacting NaCl and NaNO₃ respectively with H₂SO₄ while HBr and HI can’t be prepared by this method.

Q. 52. Cane sugar chars in concentrated sulphuric acid.

Q. 53. Concentrated sulphuric acid is a good oxidizing agent.

Q. 54. Two S-O bonds in SO₂ are equivalent.

Q. 55. Ka₂ of H₂SO₄ is << Ka₁.

Q. 56. Halogens have maximum negative electron gain enthalpy in each period.

Q. 57. Fluorine has lesser negative value of electron gain enthalpy than chlorine.

Q. 58. All halogens are colored.

Q. 59. F₂ has smaller enthalpy of dissociation than Cl₂.

Q. 60. Fluorine has lesser negative value of electron gain enthalpy than chlorine but fluorine is a stronger oxidizing agent than chlorine.

Q. 61. Fluorine shows only – 1 oxidation state. Other halogens can exhibit positive oxidation state.

Q. 62. Halogens show positive oxidation state when they combine with oxygen and fluorine atoms.

Q. 63. Halogens are good oxidizing agent and oxidizing power (reactivity) decreases with the increase in atomic number.

Q. 64. Most of reactions of fluorine are exothermic.

Q. 65. HF is a liquid while other hydrogen halides are gases.

Q. 66. HF has highest boiling point while HCl has lowest boiling point among hydrogen halides.

Q. 67. Acidity of hydrogen halides HF < HCl < HBr < HI

Q. 68. Thermal stability of hydrogen halides HF > HCl > HBr > HI

Q. 69. Thermal stability of group 16 hydrides H₆O > H₆S > H₆Se > H₆Te

Q. 70. OF₂ is fluoride of oxygen and not oxide of fluorine.

Q. 71. Oxygen and chlorine has similar electro negativity. Oxygen form hydrogen bonding but not chlorine.

Q. 72. .Ionic character of halides MF>MCl>MBr>MI

Q. 73. Electron gain enthalpy of O O- is – 141 KJ/mole and O O --> O₂- is + 702 KJ/mole. Large number of oxides having O_2- is known and not O-.

Q. 74. In metal halides, halides in higher oxidation state of the metal is more covalent than the one in lower oxidation state.(PbCl₄ is more covalent than PbCl₂)

Q. 75. Inter halogen compound is more reactive than the halogens from which it is formed.

Q. 76. Chlorine is a powerful bleaching agent.

Q. 77. HCl reacts with Fe to give FeCl₂ and not FeCl₃

Q. 78. Fluorine forms only one oxo acid HOF

Q. 79. Acidity of oxo acids HClO₄> HClO₃> HClO₂> HC1O.

Q. 80. Acidity of oxo acids HOCl>HOBr>HOI

Q. 81. Oxidizing power of HClO₄> HClO₃> HClO₂> HClO

Q. 82. Fluorine form fluoride of oxygen while other halogens form oxides of halogen.

Q. 83. Group 18 elements are chemically unreactive.

Q. 84. Group 18 elements have very high ionization enthalpy and it decreases on going down the group.

Q. 85. Group 18 elements have positive value of electron gain enthalpy.

Q. 86. Group 18 elements have lower value of boiling and melting point and it increases on going down the group.

Q. 87. Group 18 elements have larger atomic radius.

Q. 88. Bartlett synthesized XePtF6 from his knowledge of earlier known compound O₂PtF₆.

Q. 89. Xenon forms noble gas compounds.

Q. 90. Xenon forms compounds only with oxygen and fluorine.

Q. 91. Helium is used in diving apparatus.

Q. 92. Oxygen has lesser negative value of electron gain enthalpy than Sulphur.