Assertion :Nearest neighbour distance in bcc unit cell is greater than that of fcc having same edge length. Reason: Bcc has greater packing efficiency than fcc.

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
Nearest neighbours in BCC= $\frac{a \sqrt{3}}{2}$ (Body center to Body corner)

Nearest neighbours in FCC= $\frac{a}{\sqrt{2}}$ (Face center to Body corner)

Thus, the nearest neighbour distance in BCC unit cell is greater than the FCC.

The packing efficiency in BCC and FCC are as follow:

$P F_{F C C} = 0.74$ $P F_{B C C} = 0.68$

Thus the packing efficiency in FCC is greater than the BCC.

Thus, Assertion is correct but Reason is incorrect

Hence, the correct option is $C$

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Similar questions

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 distance between nearest lattice points in BCC is greater than the same in FCC having same edge length. Reason: FCC has greater packing efficiency than BCC.

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.

Q. Assertion
If BOD level of water in reservoir is less than 5 ppm it is not polluted.

Reason
High biological oxygen demand means low activity of bacteria in water.

Assertion: Be and Al have similar properties.

Reason: $B e^{2 +}$ and $A l^{3 +}$ have nearly the same charge/volume ratios and similar polarising power.

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