Assertion: Total number of octahedral voids present in unit cells of cubic close packing including the one that is present at the body center, is four.

Reason: Besides the body center there is one octahedral void present at the center of each of the six faces of the unit cell and each of which is shared between two adjacent unit cells.

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Solution

Analysing the assertion :

The octahedral voids present at the body center of the cube = $1$

$12$ octahedral voids located at each edge centre and shared between four unit cells = $(12 \times \frac{1}{4}) = 3$

Total number of octahedral voids = $4$
In ccp, number of atoms per unit cell = $4$

Number of octahedral void = number of atoms present in per unit cell

So, the assertion is correct
Analysing the reason :

Besides the body centre, there are octahedral voids at the centre of each of the $12$ edges. Each edge is shared between four adjacent unit cells. So, the reason is a wrong statement because other than the body centre, octahedral voids are present at the edge centres in cubic close packing.

Hence, the assertion is a correct statement, but the reason is a wrong statement.

So, option (C) is the correct answer.

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Similar questions

Q. Given below are two statements labelled as Assertion (A) and Reason (R).
Assertion (A): Total number of octahedral voids present in the unit cell of cubic close packing including the one that is present at the body center, is four.
Reason (R): Besides the body center there is one octahedral void present at the center of each of the six faces of the unit cell and each of which is shared between two adjacent unit cells.

Q. Assertion (A): Total number of octahedral voids present in unit cell of cubic close packing including the one that is present at the body centre, is four. Reason (R): Besides the body centre, there is one octahedral void present at the centre of each ofthe six faces of the unit cell and each of which is shared between two adjacent unit cells.

In the following questions a statement of Assertion (A) followed by a statement of Reason (R) is given. Choose the correct answer out of the following choices.

(a) Assertion and Reason both are correct statements and Reason is correct explanation for Assertion.

(b) Assertion and Reason both are correct satements but Reason is not correct explanation for Assertion.

(d) Assertion is wrong statement but Reason is correct statement.

Assertion (A) Total number of octahedral voids present in unit cell of cubic close packing including the one that is present at the body centre, is four.

Reason (R) Besides the body centre there is one octahedral void present at the centre of each of the six faces of the unit cell and each of which is shared between two adjacent unit cells.

Q. The number of octahedral void(s) per atom present in a face - centered cubic unit cell is:
[1 mark]

In the cubic close packing, the unit cell has

(a) 4 tetrahedral voids each of which is shared by four adjacent unit cell

(b) 4 tetrahedral voids within the unit cell

(d) 8 tetrahedral voids within the unit cells

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