# NEET Questions Solved

CsCl crystallises in body-centred cubic lattice. If 'a' is its edge length then which of the following expressions is correct?

(a) rCs+ + rCl- = 3a

(b)  rCs+ + rCl- = 3a/2

(c)  rCs+ + rCl- = ($\sqrt{3}$/2)*a

(d) rCs+ + rCl-$\sqrt{3a}$

(C) For bcc if edge length is a, then

rCs+ + rCl- = ($\sqrt{3}$/2)*a

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The edge length of cube is 400pm. Its body diagonal would be-

(A) 500 pm
(B) 693 pm
(C) 600 pm
(D) 566 pm

(B). Since in body centre cubic, the body diagonal
=√3a =√3 x 400pm = 692.82 pm or say 693 pm

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In an f.c.c. unit cell. atoms are numbered as shown below.The atoms not touching each other are (Atom numbered 3 is face centre of front face).

(A) 3&4
(B) 1&3
(C) 1&2
(D) 2&4

(C) Atoms along one edge or at corners do not touch each other in fee cell.

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Which is covalent solid?

(a) Fe2O3

(b) Diamond

(c) Graphite

(d) All of these

(d) All are covalent molecules. A covalent solid has atoms as constituent units at lattice points held together by covalent bonds.

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The mass of a unit cell of CsCl corresponds to:-

(a)8Cs+ and Cl-

(b)1Cs+ and 6Cl-

(c)1Cs+ and 1Cl-

(d)4Cs+ and Cl-

(c) A unit cell of CsCl having bcc structure consists of 8 atoms at the corner and one atom at centre.

Thus, no. of Cl- = 8x1/8 =1 and no. of Cs+ =1x1=1

Thus, no. of CsCl unit per unit cell = 1

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Graphite in an example of-

(A) Ionic solid

(B) Covalent solid

(C) Vander waal's crystal

(D) Metallic crystal

(B) Graphite is a covalent solid having sp2 hybridised carbon atoms.

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The intermetallic compound LiAg has a cubic crystalline structure in which each Li atom has 8 nearest neighbour silver atoms and vice-versa. What is the type of unit cell?

1. Body centred cubic

2. Face centred cubic

3. Simple cubic for either Li atoms alone or Ag atoms alone

4. None of the above

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How many octahedral and tetrahedral holes are present per unit cell in a face centred cubic arrangement of atoms?

(A) 8,4

(B) 1.2

(C) 4.8

(D) 2.1

(C) In fcc octahedral voids: at the centre = 1

at the edges = 12x1/4=3

Total =4

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TiO2 is well known example of:

(a) triclinic system

(b) tetragonal system

(c) monoclinic system

(d) none of these

(b) TiO2 has tetragonal system with five plane of symmetry and five axes of symmetry.

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Which pairs shows isomorphism?
(a) KNO3, NaNO3
(b) Cr2O3, FeO
(c) Both (a) and (b)
(d) Ferrimagnetic

(c) NaNO3 and KNO3 are not isomorphs because they have same molecular formula but different crystal structure.

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