31.

Which one of the following is aromatic?

• Cyclopentadienyl cation

• Cyclooctatetraene

• Cycloheptatriene

• Cycloheptatrienylcation

The complexes [Co(NH₃)₆][Cr(CN)₆] and [Cr(NH₃)₆][Co(CN)₆] are the examples of which type of isomerism?

• Ionisation isomerism

• Coordination isomerism

• Geometrical isomerism

• Linkage isomerism

Which of the following compounds is soluble in benzene but almost insoluble in water?

• C₂H₅OH

• CH₃CO₂H

• CH₃CHO

• C₆H₅NO₂

What is product of the following sequence of reactions?

The chemical formulae of X, Y and Z are

• X	Y	Z
  CaO	Ca(OH)2	NaOH

• NaOH

  CaO

  CaCO3

• NaOH

  Ca(OH)2

  CaCO3

• Ca(OH)2

  NaOH

  CaCO3

What is correct about the following structure?

• Total stereoisomers = 4

• Number of chiral carbons = 1

• Number of optical isomers= 2

• Number of meso compounds = 2

During estimation ofnitrogen in the organic compound by Kjeldahl's method, the ammonia evolved from 0.5 g of the compound in Kjeldahl's estimation of nitrogen, neutralised 10 mL of 1M H₂SO_4^. Find out the percentage of nitrogen in the compound.

• 14%

• 28%

• 56%

• 68%

On addition of conc. H₂SO₄ to a chloride salt, colourless fumes are evolved but in case of iodide salt, violet fumes come out. This is because

• H₂SO₄ reduces HI to I₂

• HI is of violet colour

• HI gets oxidised to I₂

• HI changes to HIO₃

Affinity for hydrogen decreases in the group from fluorine to iodine. Which ofthe halogen acids should have highest bond dissociation enthalpy?

• HF

• HCl

• HBr

• HI

Acetic anhydride is prepared in the laboratory by heating sodium acetate with

• ethyl chloride

• acetyl chloride

• conc. H₂SO₄

• zinc dust