Paper: CSIR-NET June 2011 · Subject: Physical Chemistry · Chapter: Molecular Spectroscopy · Topic: Molecular Spectroscopy – General · Marks: 2 · Difficulty: Medium
In IR spectrum of $\left[\mathrm{Co}(\mathrm{CN})_{5} \mathrm{H}\right]^{3-}$ the $\mathrm{Co}-\mathrm{H}$ stretch is observed at $1840 \mathrm{cm}^{-1}$. The $(\mathrm{Co}-\mathrm{D})$ stretch in $\left[\mathrm{Co}(\mathrm{CN})_{5} \mathrm{D}\right]^{3-}$ will appear at nearly
(a)$1300 \mathrm{cm}^{-1}$
(b)$1400 \mathrm{cm}^{-1}$
(c)$1500 \mathrm{cm}^{-1}$
(d)$1600 \mathrm{cm}^{-1}$
Answer
Answer: A ✓ checked by 4AB · confidence high
Explanation
ν ∝ 1/√μ; the Co–H/Co–D reduced-mass ratio is ≈ 2, so 1840/√2 ≈ 1300 cm⁻¹.