Q1 / 90 · JEE Main 2019 (10 Apr Shift 2) · Chemistry

The incorrect statement is.

A
The spin-only magnetic moments of ${[F e {(H_{2} O)}_{6}]}^{2 +}$ and ${[C r {(H_{2} O)}_{6}]}^{2 +}$ are nearly similar.
B
The spin-only magnetic moment of ${[N i {(N H_{3})}_{4} {(H_{2} O)}_{2}]}^{2 +}$ is $2.83 B M .$
Correct answer
C
The gemstone, ruby, has $C r^{3 +}$ ions occupying the octahedral sites of beryl.
D
The color of ${[C o C l {(N H_{3})}_{5}]}^{2 +}$ is violet as it absorbs the yellow light.

Solution

(A) {[F e {(H_{2} O)}_{6}]}^{2 +}, F e^{2 +} \to 3 d^{6} \to 4

unpaired electron

{[C r {(H_{2} O)}_{6}]}^{2 +}, C r^{2 +} \to 3 d^{4} \to 4

unpaired electron

(B) {[N i {(N H_{3})}_{4} {(H_{2} O)}_{2}]}^{2 +} = N i^{2 +} \to 3 d^{8}

\to 2

unpaired electron

μ_{m} = 2.83 B . M

(C)

In gemstone, ruby has

C r^{3 +}

ion occupying the octahedral sites of aluminium oxide

(A l_{2} O_{3})

normally occupied by

A l^{3 +}

ion.

(D)

Complimentary color of violet is yellow.

Hence, the correct answer is option: 'C'.