Subject

Chemistry

Class

NEET Class 12

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 Multiple Choice QuestionsMultiple Choice Questions

11.

ethylene can be separated from acetylene by passing the mixture through

  • fuming H2SO4

  • pyrogallol

  • ammoniacal Cu2Cl2

  • charcoal powder


C.

ammoniacal Cu2Cl2

CHCH +Cu2Cl2(ammoniacal)  CuCCCuCopper acetylide(red ppt)CH2=CH2 +Cu2Cl2(ammoniacal)  (noreaction):. Ammoniacal Cu2Cl2 is used to separate ethylene from acetylene.


12.

If it is assumed that U92235 decays only by emitting α-and (β-particles, the possible product of the decay is

  • Ac89225

  • 89227Ac

  • Ac89230

  • Ac89231


B.

89227Ac

Atomic mass (or mass number) is changed only, when an α-particle is emitted, it is not affected by the emission of β-particle.

U92235 -α Y90231 -αX88227 -β Ac89227


13.

The reaction that takes place when Cl2 gas is  passed through conc. NaOH solution is

  • oxidation

  • reduction

  • displacement

  • disproportionation


D.

disproportionation

When Cl2 gas is passed through conc NaOH solution, following reaction takes place.

  

Here, the same element undergoes oxidation and reduction simultaneously, hence it is an example of disproportionation reaction.


14.

Of the following compounds, the most acidic is

  • As2O3

  • P2O5

  • Sb2O3

  • Bi2O3


B.

P2O5

Generally, acidic nature of oxides increases along a period from left to right and decreases along a group from up to down.
Since As, P, Sb and Bi all belong to V group and arranged in the following manner :
                                  P: As, Sb, Bi
:. P2O5 is the most and Bi2O3 is the least acidic.


15.

In the compound HCC-C(CH3)=CH2 the hybridisation of C-2 and C-3 carbons are respectively

  • sp3 and sp3

  • sp2 and sp3

  • sp2 and sp

  • sp3 and sp


C.

sp2 and sp

C2= 3σ bond  sp2 hybridisationC3= 2σ bond sp hybridisation


16.

Blackened oil painting can be restored into original form by the action of

  • Cl2

  • BaO2

  • H2O2

  • MnO2


C.

H2O2

The lead of oil paintings gets converted into lead sulphide by atmospheric H2S leading to blackening of paintings. Hydrogen peroxide (H2O2) oxidises the black lead sulphide into white lead sulphate, thus restores the colour of oil painting.


17.

The two structures written below represent

             

  • pair of diastereomers

  • pair of enantiomers

  • same molecule

  • both are optically inactive


C.

same molecule

On rotating the Fischer projection by 180°, since there is no change in configuration, they are same molecule.


18.

Which of the following statements is not correct?

  • Silicon is extensively used as a semiconductor

  • Carborundum is SiC

  • Silicon occurs in free state in nature

  • Mica contains the element silicon


A.

Silicon is extensively used as a semiconductor

Silicon does not exist in free state. It exists, in nature, as silica or in the form of silicates.


19.

"Electron" is an alloy of

  • Mg and Zn

  • Fe and Mg

  • Ni and Zn

  • Al and Zn


A.

Mg and Zn

Electron, an alloy of 95% Mg and 5% Zn, is used in the construction of aircraft.


20.

The addition of HBr to 2-pentene gives

  • 2-bromopentane only

  • 3-bromopentane only

  • 2-bromopentane and 3-bromopentane

  • 1-bromopentane and 3-bromopentane


C.

2-bromopentane and 3-bromopentane

During this reaction, roughly equal quantities of the two isomers actually being obtained.