21.

Which of the following factors is of no significance for roasting sulphide ores to the oxides and not subjecting the sulphide ores to carbon reduction directly?

• Metal sulphides are thermodynamically more stable than CS₂

• CO₂ is thermodynamically more stable than CS₂

• Metal sulphides are less stable than the corresponding oxides

• Metal sulphides are less stable than the corresponding oxides

The absolute configuration of 

• S,S

• R,R

• R,S

• R,S

• 0.26

• 0.399

• 0-399

• 0-399

The vapour pressure of water at 20^oC is 17.5 mm Hg. If 18 g of glucose (C₆H₁₂O₆) is added to 178.2 g of water at 20^oC, the vapour pressure of the resulting solution will be

• 17.675 mm Hg

• 15.750 mm Hg

• 16.500 mm Hg

• 16.500 mm Hg

In a compound atoms of element Y from ccp lattice and those of element X occupy 2/3rd of tetrahedral voids. The formula of the compound will be 

• X₄Y₃

• X₂Y₃

• X₂Y

• X₂Y

Gold numbers of protective colloids A, B, C and D are 0.50, 0.01, 0.10 and 0.005, respectively. The correct order of their protective powers is

•  D < A < C < B

• C < B < D < A

•  A < C < B < D

•  A < C < B < D

Toluene is nitrated and the resulting product is reduced with tin and hydrochloric acid. The product so obtained is diazotised and then heated with cuprous bromide. The reaction mixture so formed contains

• mixture of o− and p−bromotoluenes

• mixture of o− and p−dibromobenzenes

• mixture of o− and p−bromoanilines

• mixture of o− and p−bromoanilines

The organic chloro compound, which shows complete stereochemical inversion during a S_N2 reaction,is

• (C₂H₅)₂CHCl 

•  (CH₃)₃CCl

• (CH₃)₂CHCl

• (CH₃)₂CHCl

Phenol, when it first reacts with concentrated sulphuric acid and then with concentrated nitric acid,gives 

• 2,4,6-trinitrobenzene

• o-nitrophenol

• p-nitrophenol

• p-nitrophenol

In the following sequence of reactions, the alkene affords the compound ‘B’

The compound B is

• CH₃CH₂CHO

• CH₃COCH₃

• CH₃CH₂COCH₃

• CH₃CH₂COCH₃