Subject

Chemistry

Class

NEET Class 12

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 Multiple Choice QuestionsMultiple Choice Questions

31.

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

Al2O3(s) + 2OH-(aq)  2Al2O2-(aq) + H2O(l)

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

2Al(OH)4-  Al2O3·3H2O(s) +2OH-(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


B.

temperature and pressure are dropped and the super saturated solution seeded

Industrially, in the extraction of alumina, temperature and pressure are dropped and the super saturated solution seeded. Sometimes CO2 is also used to precipitate alumina.


32.

Reaction of R OH with R' MgX produces

  • RH

  • R' H

  • R - R

  • R'- R'


C.

R - R

[Remember: H directly bonded with N or O or F is acidic in nature.]


33.

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

  • K2Cr2O7/H2SO4

  • Zn-Hg/HCl

  • SeO2

  • Iodine/NaOH


D.

Iodine/NaOH

Ketones having CH3CO- group give yellow coloured iodoform with Iand NaOH

CH3CH2CH2C||OCH3 + I2+NaOH CHI3 + CH3CH2CH2COONa + NaI + H2O2-pentanone                                        iodoformCH3CH2C||OCH2H3 + I2+NaOH no reaction

:. I2 NaOH is used to distinguish between 2-pentanone and 3-pentanone.


34.

Which one of the following is called a carbylamine?

  • RCN

  • RCONH2

  • RCH= NH

  • RNC


D.

RNC

Isocyanides, ie, compounds having -NC group are also known as carbyl amine.
:. RNC is alkyl carbylamine


35.

The oxidant which is used as an antiseptic is

  • KBrO3

  • KMnO4

  • CrO3

  • KNO3


B.

KMnO4

KMnO4 is a powerful oxidising agent in all mediums and it is used as an antiseptic.


36.

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


C.

Phenol liberates CO2 from Na2CO3 solution

Only the acids stronger than carbonic acid are able to liberate COfrom Na2CO3, solution. Since, phenol is a weak acid, it does not liberate COfrom Na2CO3  solution.


37.

The catalyst used for olefin polymerisation is

  • Ziegler-Natta catalyst

  • Wilkinson catalyst

  • Raney nickel catalyst

  • Merrifield resin


A.

Ziegler-Natta catalyst

Ziegler Natta catalyst [TiCl4 + Al(C2H5)3] is used as a catalyst in the polymerisation of olefins.


38.

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

  • Hydrogen bond

  • Covalent bond

  • Disulphide bond

  • van der Waals' force


A.

Hydrogen bond

According to double helical model of DNA (proposed by Watson and Crick), DNA molecule contains two deoxyribonuclide chains which are spirally coiled around each other on a common axis. These two chains are held together by the formation of hydrogen bonds,

                              


39.

The monomer used to produce orlon is

  • CH2=CHF

  • CH2=CCl2

  • CH2=CHCl

  • CH2=CH-CN


D.

CH2=CH-CN

Orlon is poly vinyl cyanide which is a polymer of vinyl cyanide (or acrylonitrile).


40.

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

  • Cannizaro reaction

  • Wurtz reaction

  • Aldol condensation

  • Friedel-Craft reaction


A.

Cannizaro reaction

D.

Friedel-Craft reaction

(a)2HCHO Conc. NaOH HCH2OH + HCOONa                                                                        (Cannizaroreaction)

(b) 

(c) 

(d)