Question

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 true, reason is correct explanation of assertion.
(b) Assertion and reason both are true but reason is not the correct explanation of assertion.
(c) Assertion is true, reason is false.
(d) Assertion is false, reason is true.

Assertion (A) $\left[Fe\right(CN{)}_6{]}^{3-}$ ion shows magnetic moment corresponding to two unpaired electrons.
Reason (R) Because it has $d^{2}s{p}^3$ type hybridisation.

Answer 1

Answer: (d). The assertion is false but the reason is true.
According to VBT, MOEC of $F{e}^{3+}$ in $\left[Fe\right(CN{)}_6{]}^{3-}$ is


Hybridisation = $d^{2}s{p}^3$
n=1
Hence, correct assertion is
$\left[Fe\right(CN{)}_6{]}^{3-}$ ion shows magnetic moment corresponding to one unpaired electron.
i.e., $\mu =\sqrt{n(n+2)}=\sqrt{1(1+2)}=\sqrt{3}=1.73Bm$