 JEE Mains Previous Years Questions with Solutions

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1

AIEEE 2005

Lattice energy of an ionic compounds depends upon
A
Charge on the ion only
B
Size of the ion only
C
Packing of ions only
D
Charge on the ion and size of the ion

Explanation

Electrostatic force of attraction between cation and anion is called Lattice energy.

Lattice energy (F) = $K{{{q_1}{q_2}} \over {{r^2}}}$

q1 and q2 are the charges of cations and anion. So Lattice energy depens on the charges of ions.

r = distance between center of ions

And, r = r+ + r- where r+ = radius of cation and r- = radius of anion

So, more the size of ions less the value of Lattice energy.
2

AIEEE 2004

The maximum number of 90° angles between bond pair of electrons is observed in
A
dsp3 hybridization
B
sp3d2 hybridization
C
dsp2 hybridization
D
sp3d hybridization

Explanation Here eight 90o angles between bond pair and bond pair. Those angles are $\angle$1M2, $\angle$2M3, $\angle$3M4, $\angle$4M1, $\angle$5M1, $\angle$5M2, $\angle$5M3, $\angle$5M4. Here twelve 90o angles between bond pair and bond pair. Those angles are $\angle$1M2, $\angle$2M3, $\angle$3M4, $\angle$4M1, $\angle$5M1, $\angle$5M2, $\angle$5M3, $\angle$5M4, $\angle$6M1, $\angle$6M2, $\angle$6M3, $\angle$6M4. Here four 90o angles between bond pair and bond pair. Those angles are $\angle$1M2, $\angle$2M3, $\angle$3M4, $\angle$4M1. Here six 90o angles between bond pair and bond pair. Those angles are $\angle$1M3, $\angle$1M4, $\angle$1M5, $\angle$2M3, $\angle$2M4, $\angle$2M5.
3

AIEEE 2004

Which one of the following has the regular tetrahedral structure?
(Atomic nos : B = 5, S = 16, Ni = 28, Xe = 54)
A
XeF4
B
[Ni(CN)4]2-
C
$BF_4^-$
D
SF4

Explanation

Regular Tetrahedral structure is possible in sp3 hybridization where central atom has 4 bond pair and no lone pair.

(a)   XeF4  is sp3d2 hybridised and structure is square planar. (b)   [Ni(CN)4]$-$2 is coordinate compound and oxidation number of Ni is +2.

Electronic configuration of Ni+2 is $=$ [Ar]3d8 But because of CN$-$ ion which is a strong field ligand , it can perform pairing of electron. And the structure of dsp2 hybridization is square planar. (C) $\,\,\,\,$ BF$_4^ -$, 4 bond pair present so angle is 109o 28' and sp3 hybridised. So structure is regular tetrahedral. (d) SF4 is sp3d hybridised and structure is see-saw.
4

AIEEE 2004

The states of hybridization of boron and oxygen atoms in boric acid (H3BO3) are respectively
A
sp2 and sp2
B
sp3 and sp3
C
sp3 and sp2
D
sp2 and sp3

Explanation

Structure of  H3BO3  is Here Boron has 3 sigma bond. So it is sp2 hybridised.

And oxygen has two sigma bond and two lone pair. So it sp3 hybridised.