Subject

Chemistry

Class

NEET Class 12

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 Multiple Choice QuestionsMultiple Choice Questions

11.

What is the H of the reaction?

CH2Cl2 (g) C (g) + 2H (g) + 2Cl (g)

The average bond energies of C-Cl bond and C-H bond are 416 kJ and 325 kJ mol-1 respectively.

  • 1482 kJ

  • 1482 J

  • 1492 kJ

  • 1492 J


A.

1482 kJ

In the reaction, two moles of C-H bonds and two moles of C-Cl bonds are broken. Hence, energy absorbed is

 = 2 x 416 + 2 x 325

 = 1482kJ


12.

Which of the following is a Lewis acid ?

  • OH-

  • H+

  • F-

  • NH3


B.

H+

Lewis acid is any substance that can accept a pair of non- bonding electrons, such as the H+ ions. It is an electron pair acceptor.

Lewis base is any substance that can donate a pair of electrons.

OH-, F- and NH3 are Lewis base because they can donate a lone pair of electrons while H+ is a Lewis acid because it can accept a lone pair of electrons.


13.

The bond length of HCl bond is 2.29 x 10-10 m. The percentage ionic character of HCl, if measured dipole moment is 6.226 x 10-30 C- m, is

  • 8%

  • 20%

  • 17%

  • 50%


C.

17%

μcal = e x d = 1.6 x 10-19 x 2.29 x 10-10

     = 3.664 x 10-29 C-m

% ionic character = μexpμcal = 6.226 x 10-303.664 ×10-29 ×100

                           = 17%


14.

The only o  p-directing group which is deactivating in nature is

  • -NH2

  • -OH

  • -X(halogens)

  • -R(alkyl groupd)


D.

-R(alkyl groupd)

-NH2, -OH and -R (alkyl groups) all are o/p- directing and they activates the benzene ring -(X) halogens are however o/p-directing but deactivate the benzene ring by withdrawing electrons fron the ring due to -I effect.


15.

Which of the following is a wrong statement ? In a given period of the Periodic Table, the s-block element has, in general, a higher value of

  • electronegativity

  • atomic radius

  • ionisation energy

  • electron affinity


B.

atomic radius

Electronegativity, ionisation energy and electron affinity of s-block elements in their respective period is low but the atomic radius of the s-block elements is larger in their respective period due to less effective nuclear charge.


16.

The IUPAC name of the following compound is

 

  • 1, 2-dimethyl-2-butenol

  • 3-methylpent-3-en-2-ol

  • 3, 4-dimethyl-2-buten-4-ol

  • None of the above


B.

3-methylpent-3-en-2-ol

IUPAC name of the above compound is 3-methylpent-3-en-2-ol


17.

Ammonia gas can be dried over

  • CaCl2

  • conc. H2SO4

  • P2O5

  • quick lime


D.

quick lime

Ammonia is dried over quick lime (CaO). It cannot be dried over conc. H2SO4, P2O5 and CaCl2 because it reacts with these compounds.


18.

Which of the organic compounds will give red colour in Lassaigne test ?

  • C6H5NH2

  • None of these


B.

If both nitrogen and sulphur are present in a organic compound, they will give red blood colour with Lassaigne test due to the formation of ferric thiocyanate.

Na + C + S + N  NaSCN (sodium thiocyanate)

Fe3+ + 3NaSCN Fe(SCN)3 + 3Na+

                            ferric thiocyanate


19.

CaC2 and H2O react to produce

  • CH4

  • C2H4

  • C2H2

  • C2H6


C.

C2H2

CaC2 and H2O reacts to produce C2H2 (acetylene gas).

CaC2(s) + 2H2O(l)  Ca(OH)2(aq) + C2H2


20.

Inorganic benzene is

  • B3N6H3

  • B3N3H6

  • Al3N3H6

  • None of these


B.

B3N3H6

B3N3H6 (borazine) is known as inorganic benzene. Borazine is isoelectronic, i.e. same number of electrons and isosteric, i.e. same number of atoms with benzene.