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Test: Number of Atoms in a Unit Cell & Closed-Packed Structures (Old NCERT) - NEET MCQ


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25 Questions MCQ Test Chemistry Class 12 - Test: Number of Atoms in a Unit Cell & Closed-Packed Structures (Old NCERT)

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Test: Number of Atoms in a Unit Cell & Closed-Packed Structures (Old NCERT) - Question 1

For the structure given below the site marked as S is a
For the structure given below the site marked as S is a:

Detailed Solution for Test: Number of Atoms in a Unit Cell & Closed-Packed Structures (Old NCERT) - Question 1

Octahedral voids occupy the position of edge centre and body centre.

Test: Number of Atoms in a Unit Cell & Closed-Packed Structures (Old NCERT) - Question 2

Which of the following statements is not about the voids?

Detailed Solution for Test: Number of Atoms in a Unit Cell & Closed-Packed Structures (Old NCERT) - Question 2

Octahedral sites are created by overlapping two equilateral triangles with apices in opposite directions.

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Test: Number of Atoms in a Unit Cell & Closed-Packed Structures (Old NCERT) - Question 3

In ABC packing if the number of atoms in the unit cell is n then the number of tetrahedral voids in the unit cell is equal to:

Detailed Solution for Test: Number of Atoms in a Unit Cell & Closed-Packed Structures (Old NCERT) - Question 3

Number of tetrhedral voids per atom in a unit cell is 2.
Hence the total numberof tetrahedral voids =2n.

Test: Number of Atoms in a Unit Cell & Closed-Packed Structures (Old NCERT) - Question 4

If the radius of an octahedral void is r and the radius of atoms in close packing is R, then the relation between r and R is :

Detailed Solution for Test: Number of Atoms in a Unit Cell & Closed-Packed Structures (Old NCERT) - Question 4


(2R)2 = (R + r)2 + (R + r)2
√2 R = R + r
(√2 - 1)R = r
0.414R = r

Test: Number of Atoms in a Unit Cell & Closed-Packed Structures (Old NCERT) - Question 5

A metal crystallises into a lattice containing a sequence of layers as AB AB AB ... . What percentage of voids are left in the lattice?

Detailed Solution for Test: Number of Atoms in a Unit Cell & Closed-Packed Structures (Old NCERT) - Question 5

ABAB packing is hexagonal closepacking in which all atoms occupy 74% of the total space. Hence, 26% of voids are left in the lattice.

Test: Number of Atoms in a Unit Cell & Closed-Packed Structures (Old NCERT) - Question 6

In ccp arrangement the pattern of successive layers can be designated as

Detailed Solution for Test: Number of Atoms in a Unit Cell & Closed-Packed Structures (Old NCERT) - Question 6

In ccp pattern, fourth layer is identical to first layer.

Test: Number of Atoms in a Unit Cell & Closed-Packed Structures (Old NCERT) - Question 7

Which of the following statements is not correct about hexagonal close packing?

Detailed Solution for Test: Number of Atoms in a Unit Cell & Closed-Packed Structures (Old NCERT) - Question 7

The coordination number is 12

Test: Number of Atoms in a Unit Cell & Closed-Packed Structures (Old NCERT) - Question 8

A crystalline structure has radius ratio (r+/r-)  in the range of 0.225 - 0.414. The coordination number and arrangement of anions around the cations are:

Detailed Solution for Test: Number of Atoms in a Unit Cell & Closed-Packed Structures (Old NCERT) - Question 8

If the radius ratio is between 0.225 and 0.414, it will have a tetrahedral void. The derivation of this actually takes place in reverse where we assume a tetrahedral void and arrive at the value, but the converse also holds true. A tetrahedral void naturally means there are 4 surrounding atoms. So, coordination number will be 4.

Test: Number of Atoms in a Unit Cell & Closed-Packed Structures (Old NCERT) - Question 9

A Crystal lattice with alternate +ve "and "-veions has radius ratio of 0.524. The coordination number of lattice is

Detailed Solution for Test: Number of Atoms in a Unit Cell & Closed-Packed Structures (Old NCERT) - Question 9

Coordination number of crystal lattices which fall in the range of 0.414 - 0.732 is 6.

Test: Number of Atoms in a Unit Cell & Closed-Packed Structures (Old NCERT) - Question 10

A solid AB has a rock salt structure. If radius of cation A+ is 120 pm, what is the minimum value of radius of B anion?

Detailed Solution for Test: Number of Atoms in a Unit Cell & Closed-Packed Structures (Old NCERT) - Question 10

Limited Ratio 

⟹rB− = 290 pm

Test: Number of Atoms in a Unit Cell & Closed-Packed Structures (Old NCERT) - Question 11

A crystal formed by two elements X and Y in cubic structure. X atoms are at the corners of cube while Y atoms are at the face center. The formula of he compound will be:

Detailed Solution for Test: Number of Atoms in a Unit Cell & Closed-Packed Structures (Old NCERT) - Question 11

No. of X atom (at the corners) = 1/8 x 8 = 1
No. of Y atoms (fcc) = 6 × 1/2 = 3
hence, the formula is XY

Test: Number of Atoms in a Unit Cell & Closed-Packed Structures (Old NCERT) - Question 12

If three elements X,Y and Z crystallizes in a ccp lattice with the X atoms at the corner, Y atoms at the cube centre and Z atom at the edge centre the formula of the compound will be:

Detailed Solution for Test: Number of Atoms in a Unit Cell & Closed-Packed Structures (Old NCERT) - Question 12

No. of X atoms = 1/8 x 8 = 1
No. of Y atoms = 1
No. of Z atoms = 12 x 1/4 = 3
Formula of the compound = XYZ3

Test: Number of Atoms in a Unit Cell & Closed-Packed Structures (Old NCERT) - Question 13

A compound is formed by two elements Y and Z. The element Z forms ccp and atoms Y occupy 1/3rd of tetrahedral voids. The formula of the compound is

Detailed Solution for Test: Number of Atoms in a Unit Cell & Closed-Packed Structures (Old NCERT) - Question 13

Suppose no. of atoms of Z = a

No. of tetrahedral voids = 2a

No. of atoms of Y = 1/3 × 2a = 2a/3

Ratio of atoms of y and Z= 2a/3 : a = 2:3

Hence, the formula of the compound = Y2Z3

Test: Number of Atoms in a Unit Cell & Closed-Packed Structures (Old NCERT) - Question 14

A cubic solid is made up of two elements P and Q. Atoms of P are present at the corners of the cube and atoms of Q are present by body centre. What is the formula of the compound and what are coordination number of P and Q?

Detailed Solution for Test: Number of Atoms in a Unit Cell & Closed-Packed Structures (Old NCERT) - Question 14

No. of atoms of P = 8 x 1/8 = 1
No. of atoms of Q = 1 x 1 = 1
The formula of the compound is PQ. Coordination no. of P and Q = 8:8

Test: Number of Atoms in a Unit Cell & Closed-Packed Structures (Old NCERT) - Question 15

How many chloride ions are surrounding sodium ion in a sodium chloride crystal?

Detailed Solution for Test: Number of Atoms in a Unit Cell & Closed-Packed Structures (Old NCERT) - Question 15

Each Na+ ion is surrounded by 6 Cl-ions and each Cl- ion is surrounded by 6 Na+ ions in NaCl crystal.

Test: Number of Atoms in a Unit Cell & Closed-Packed Structures (Old NCERT) - Question 16

In NaCl structure,

Detailed Solution for Test: Number of Atoms in a Unit Cell & Closed-Packed Structures (Old NCERT) - Question 16

Octahedral sites are occupied by Na+ ions in NaCl structure.

Test: Number of Atoms in a Unit Cell & Closed-Packed Structures (Old NCERT) - Question 17

NaCl type crystal (with coordination no. 6:6) can be converted into CsCl type crystal (with coordination no. 8:8) by applying:

Detailed Solution for Test: Number of Atoms in a Unit Cell & Closed-Packed Structures (Old NCERT) - Question 17

Increase of pressure increases coordination number. Hence, by applying high pressure, NaCl type crystal can be changed into CsCl type crystal

Test: Number of Atoms in a Unit Cell & Closed-Packed Structures (Old NCERT) - Question 18

Coordination number of Cs+ and Cl- in CsCl crystal are:

Detailed Solution for Test: Number of Atoms in a Unit Cell & Closed-Packed Structures (Old NCERT) - Question 18

CsCl has a bcc structure. Each Cs ion is surrounded by 8 Cl ions and each Cl ion is surrounded by 8 Cs+ ions. CsCl has a bcc type structure. Thus, the structure has 8 : 8 coordination number.

Test: Number of Atoms in a Unit Cell & Closed-Packed Structures (Old NCERT) - Question 19

In zinc blende structure,

Detailed Solution for Test: Number of Atoms in a Unit Cell & Closed-Packed Structures (Old NCERT) - Question 19

ZnS has a ccp structure. S2− ions are present at the corners of the cube and centre of each face. Zn2+ ions occupy half of the tetrahedral sites. Each Zn2+ ion is surrounded by four S2− ions and each S2− ion is surrounded by four Zn2+ ions.

Test: Number of Atoms in a Unit Cell & Closed-Packed Structures (Old NCERT) - Question 20

Consider the unit cell given below :

The unit cell shown in the figure belongs to

Detailed Solution for Test: Number of Atoms in a Unit Cell & Closed-Packed Structures (Old NCERT) - Question 20

ZnS has a ccp structure. S2- ions at the corners of the cube and centre of each face. Zn2+ ions occupy half of the tetrahedral sites. Each Zn2+ ion is surrounded by four S2- ions and each S2- ion is  surrounded by four Zn2+ ions.

Test: Number of Atoms in a Unit Cell & Closed-Packed Structures (Old NCERT) - Question 21

Consider the unit cell given below :

The coordination number of Y will be

Detailed Solution for Test: Number of Atoms in a Unit Cell & Closed-Packed Structures (Old NCERT) - Question 21

Coordination no. of Y (Zn2+) is 4.

Test: Number of Atoms in a Unit Cell & Closed-Packed Structures (Old NCERT) - Question 22

Consider the unit cell given below :

Which of the following about the above structure is not correct?

Detailed Solution for Test: Number of Atoms in a Unit Cell & Closed-Packed Structures (Old NCERT) - Question 22

Each X ion is surrounded by 4Y ions.

Test: Number of Atoms in a Unit Cell & Closed-Packed Structures (Old NCERT) - Question 23

In  CaF2 type (fluorite structure),  Ca2+ ions form__(A)___ structure and F ions are present in all  __(B)___ voids. The coordination number of Ca2+ is ___(C)___ and F  is___(D)____.
(A), (B), (C) and (D) respectively are:

Detailed Solution for Test: Number of Atoms in a Unit Cell & Closed-Packed Structures (Old NCERT) - Question 23

Ca2+ ions form ccp structure while F- ions in all tetrahedral holes and coordination numbers are 8 and 4.

Test: Number of Atoms in a Unit Cell & Closed-Packed Structures (Old NCERT) - Question 24

A unit of BaCl2 (fluorite structure) is made up of:

Detailed Solution for Test: Number of Atoms in a Unit Cell & Closed-Packed Structures (Old NCERT) - Question 24

In fluorite structure, cations form ccp structure and anions are present in all tetrahedral holes. Hence, no. of Ba2+ ions =8 and no. of Cl− ions = 4

Test: Number of Atoms in a Unit Cell & Closed-Packed Structures (Old NCERT) - Question 25

Which of the following structures is not correctly matched ?

Detailed Solution for Test: Number of Atoms in a Unit Cell & Closed-Packed Structures (Old NCERT) - Question 25

In NaCl type, Clions form ccp structures while Na+ ions are present in all octahedral voids.

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