Which one of the following statements regarding helium is incorrect ?

• It is used to fill gas balloons instead of hydrogen because it is lighter and non-inflammable

• It is used as a cryogenic agent for carrying out experiments at low temperatures

• It is used to produce and sustain powerful superconducting magnets

• It is used in gas cooled nuclear reactors

Which one of the following arrangements represents the correct order of electron gain enthalpy (with negative sign) of the given atomic species?

• Cl <F <S <CO

• O <S <F <Cl

• S <O <Cl <F

• F <Cl <O <S

523.

Bleaching action of bleaching powder is due to

• Cl

• O

• Ca

• Cl₂

Sodium thiosulphate is used in photography

• as AgBr grain is reduced to non-metallic silve

• to convert metallic silver into silver salt

• to remove reduced silver

• to remove undecomposed AgBr in the form of Na₃[Ag(S₂O₃)₂] (a complex salt)

The decreasing order of electron affinity is

• I > Br > Cl > F 

• Br > Cl > F > I

• F > Cl > Br > I

• Cl > F > Br > I

For the reaction, 2SO₂ + O₂(excess) → 2SO₃ the order of reaction with respect to O₂ is

• two

• three

• zero

• one

In the manufacture of ammonia by Haber's process, N₂ (g) + 3H₂(g) $\rightleftharpoons$2NH₃(g) + 92.3kJ. which of the following conditions is unfavourable?

• reducing the temperature

• Removing ammonia as it is formed

• Increasing the temperature

• Increasing the pressure

Red lead is

• PbO

• Pb₃O₄

• PbO₂

• Pb₄O₃

Concentrated HNO₃ forms NO${}_2^{+}$ in the presence of

• Conc. H₂SO₄

• Fe

• FeBr₃

• AlCl₃

The key step in the manufacturing of H₂SO₄ by contact process is

• absorption of SO₃ in H₂SO₄ to give oleum

• dilution of oleum with water

• burning of sulphur in air to generate SO₂

• catalytic oxidation of SO₂ with O₂ to give SO₃