In the conversion of Br₂ to Br${}_3^{-}$, the oxidations number of Br changes from:

• zero to +5

• +1 to +5

• zero to -3

• +2 to +5

Hydrogen bond is strongest in :

• S-H····O

• O-H····S

• F-H····F

• O-H····N

Liquor ammonia bottles are opened only after cooling. This is because

• it is only a mild explosive

• it is a corrosive liquid

• it is a lachrymatory

• it generates high vapour pressure and mild explosive

A transition metal ion exists in its highest oxidation state. It is expected to behave as :

• a chelating agent

• a central metal in a coordination compound

• an oxidising agent

• a reducing agent

Chemical reactions with very high E_a values are generally :

• very fast

• very slow

• moderately fast

• spontaneous

Which of the following does not conduct electricity?

• Fused NaCl

• Solid NaCl

• Brine solution

• Copper

Osmotic pressure observed when benzoic add is dissolved in benzene is less than that expected from theoretical considerations. This is because:

• benzoic acid is an organic solute

• benzoic acid has higher molar mass than benzene

• benzoic acid gets assoicated in benzene

• benzoic acid gets dissociated in benzene

An example for autocatalysis is :

• oxidation of NO to NO₂

• oxidation of SO₂ to SO₃

• decomposition of KClO₃ to KCl and O₂

• oxidation of oxalic acid by acidified KMnO₄

29.

Which of the following taking place in the blast furnace is endothermic?

• CaCO₃ → CaO + CO₂

• 2C + O₂ → 2CO

• C + O₂ → CO₂

• Fe₂O₃ + 3CO → 2Fe + 3CO₂

The formation of O${}_2^{+}$[PtF₆]^- is the basis for the formation of xenon fluorides. This is because :

• O₂ and Xe have comparable size

• Both O₂ and Xe are gases

• O₂ and Xe have both comparable ionisation size energies and comparable sizes.

• O₂ and Xe have comparable electro- negativities.