31.

In aluminium extraction by the Bayer process, alumina is extracted from bauxite by sodium hydroxide at high temperatures and pressures

${\mathrm{Al}}_2{\mathrm{O}}_3\left(\mathrm{s}\right) + 2{\mathrm{OH}}^{-}\left(\mathrm{aq}\right) \to 2{\mathrm{Al}}_2{\mathrm{O}}_2^{-}\left(\mathrm{aq}\right) + {\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)$

Solid impurities such as Fe₂O₃ and SiO₂ are removed and then Al(OH)₄^- is reprecipitated

$2\mathrm{Al}(\mathrm{OH}{)}_4^{-} \to {\mathrm{Al}}_2{\mathrm{O}}_3·3{\mathrm{H}}_2\mathrm{O}(\mathrm{s}) +2{\mathrm{OH}}^{-}(\mathrm{aq}).$In the industrial world

 

• carbon dioxide is added to precipitate the alumina

• temperature and pressure are dropped and the super saturated solution seeded

• both (A) and (B) are practised

• the water is evaporated

Reaction of R OH with R' MgX produces

• RH

• R' H

• R - R

• R'- R'

For making distinction between 2-pentanone and 3-pentanone, the reagent to be employed is

• K₂Cr₂O₇/H₂SO₄

• Zn-Hg/HCl

• SeO₂

• Iodine/NaOH

Which one of the following is called a carbylamine?

• RCN

• RCONH₂

• RCH= NH

• RNC

The oxidant which is used as an antiseptic is

• KBrO₃

• KMnO₄

• CrO₃

• KNO₃

Which statement is incorrect?

• Phenol is a weak acid

• Phenol is an aromatic compound

• Phenol liberates CO₂ from Na₂CO₃ solution

• Phenol is soluble in NaOH

The catalyst used for olefin polymerisation is

• Ziegler-Natta catalyst

• Wilkinson catalyst

• Raney nickel catalyst

• Merrifield resin

Which of the following contributes to the double helical structure of DNA ?

• Hydrogen bond

• Covalent bond

• Disulphide bond

• van der Waals' force

The monomer used to produce orlon is

• ${\mathrm{CH}}_2=\mathrm{CHF}$

• ${\mathrm{CH}}_2={\mathrm{CCl}}_2$

• ${\mathrm{CH}}_2=\mathrm{CHCl}$

• ${\mathrm{CH}}_2=\mathrm{CH}-\mathrm{CN}$

In which of the following reactions new carbon-carbon bond is not formed ?

• Cannizaro reaction

• Wurtz reaction

• Aldol condensation

• Friedel-Craft reaction