Assertion :An important feature of Fluorite structure is that cations being large in size occupy FCC lattice points whereas anions occupy all the tetrahedral voids giving the formula unit $A B_{2}$ (A: cation, B: anion). Reason: There are 6 cations and 12 anions per FCC unit cell of the Fluorite structure.

Both Assertion and Reason are correct and Reason is the correct explanation for Assertion

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Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion

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Assertion is correct but Reason is incorrect

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Assertion is incorrect but Reason is correct

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Solution

The correct option is C Assertion is correct but Reason is incorrect
Cations occupy FCC lattice in fluorite $(C a F_{2})$ structure and anions occupy all the tetrahedral voids.

No. of cation per unit cell $= 8 \times \frac{1}{8} + 6 \times \frac{1}{2} = 4$
No. of anion per unit cell $= 8$ (No. of Tetrahedral voids)
$= 8$

Therefore (C) Assertion is correct but the reason is incorrect.

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Similar questions

STATEMENT-1: An important feature of Fluorite structures is that cations being large in size occupy FCC lattice points whereas anions occupy all the tetrahedral voids giving the formula unit

A B_{2}

(A: cation, B: anion).

STATEMENT-2: There are 6 cations and 12 anions per FCC unit cell of the Fluorite structure.

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 an 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) The packing efficiency is maximum for the fcc structure.

Reason (R) The coordination number is 12 in fcc structures.

Q. Assertion: The compressibility factor for

H_{2}

and

H e

(1 + \frac{P b}{R T})

Reason: The compressibility factor for

H_{2}

and

H e

can be derived from Van der Waal's equation.

Assertion: All the points (1, 0), (-1, 0), (2, 0) and (5, 0) lie on the x – axis.
Reason: Equation of the x-axis is y = 0

Choose the correct option.

Assertion (A) Bond angle in ethers is slightly less than the tetrahedral angle.
Reason (R) There is a repulsion between the two bulky (- R) groups.
(a) Assertion and reason both are correct and reason is correct explanation of assertion.
(b) Assertion and reason both are wrong statements.
(c) Assertion is correct statement but reason is wrong statement.
(d) Assertion is wrong statement but reason is correct statement.
(e) Both assertion and reason are correct statements but reason is not correct explanation of assertion.

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