
70. For the given compounds, the correct order of
increasing pKa value :
(A)
(B)
(C)
(D)
(E)
(1) (E) < (D) < (C) < (B) < (A)
(2) (D) < (E) < (C) < (B) < (A)
(3) (E) < (D) < (B) < (A) < (C)
(4) (B) < (D) < (A) < (C) < (E)
Ans. BONUS
NTA Ans. (4)
Sol. Acidic strength order :-
B > D > C > A > E
Correct pKa Order :
B < D < C < A < E
All options are incorrect.
71. Given below are two statements : one is labelled as
Assertion (A) : and the other is labelled as Reason (R).
Assertion (A) : Both rhombic and monoclinic
sulphur exist as S8 while oxygen exists as O2.
Reason (R) : Oxygen forms p-p multiple bonds
with itself and other elements having small size
and high electronegativity like C, N, which is not
possible for sulphur.
In the light of the above statements, choose the
most appropriate answer from the options given
below :
(1) Both (A) and (R) are correct and (R) is the
correct explanation of (A).
(2) Both (A) and (R) are correct but (R) is not the
correct explanation of (A).
(3) (A) is correct but (R) is not correct.
(4) (A) is not correct but (R) is correct.
Ans. (3)
Sol. Oxygen can form 2p-2p multiple bond with
itself due to its small size while sulphur cannot
form multiple bond with itself as 3p-3p bond
will be unstable due to large size of sulphur, but
sulphur can form multiple bond with small size
atom like C and N.
eg. S=C=S
S=C=N–
72. Given below are two statements : one is labelled as
Assertion (A) and the other is labelled as Reason (R).
Assertion (A): The total number of geometrical
isomers shown by [Co(en)2Cl2]+ complex ion is three
Reason (R): [Co(en)2Cl2]+ complex ion has an
octahedral geometry.
In the light of the above statements, choose the most
appropriate answer from the options given below :
(1) Both (A) and (R) are correct and (R) is the
correct explanation of (A).
(2) (A) is correct but (R) is not correct.
(3) (A) is not correct but (R) is correct.
(4) Both (A) and (R) are correct but (R) is not the
correct explanation of (A).
Ans. (3)
Sol. [Co(en)2Cl2]+ has octahedral geometry with two
geometrical isomers.
73. The electronic configuration of Cu(II) is 3d9
whereas that of Cu(I) is 3d10. Which of the
following is correct ?
(1) Cu(II) is less stable
(2) Stability of Cu(I) and Cu(II) depends on nature
of copper salts
(3) Cu(II) is more stable
(4) Cu(I) and Cu(II) are equally stable
Ans. (3)
Sol. Cu(II) is more stable than Cu(I) because hydration
energy of Cu+2 ion compensate IE2 of Cu.