Q42 · CSIR NET Chemistry, December 2019
Paper: CSIR NET December 2019 · Subject: Physical Chemistry · Chapter: Group Theory · Topic: Group Theory – General · Marks: 2 · Difficulty: Hard
The observed IR spectrum of $\mathrm{BCl_3}$ exhibits three bands at 995, 480 and 244 $\mathrm{cm^{-1}}$, while the Raman bands are observed at 995, 471 and 244 $\mathrm{cm^{-1}}$. Given that for $\mathrm{BCl_3}$ $\Gamma_{vib} = A_1' + 2E' + A_2''$, the frequency of $A_1'$ mode in $\mathrm{cm^{-1}}$ is
| $D_{3 h}$ | E | $2 C_{3}$ | $3 C_{2}$ | $\sigma_{h}$ | $2 S_{3}$ | $3 \sigma_{v}$ | |
|---|---|---|---|---|---|---|---|
| $A_{I}{ }^{\prime}$ | 1 | 1 | 1 | 1 | 1 | 1 | $x^{2}+y^{2}, z^{2}$ |
| $A_{2}{ }^{\prime}$ | 1 | 1 | -1 | 1 | 1 | -1 | $R_{z}$ |
| $E^{\prime}$ | 2 | -1 | 0 | 2 | -1 | 0 | $(x, y)$ |
| $A_{1}{ }^{\prime \prime}$ | 1 | 1 | 1 | -1 | -1 | -1 | |
| $A_{2}{ }^{\prime \prime}$ | 1 | 1 | -1 | -1 | -1 | 1 | $z$ |
| $E^{\prime \prime}$ | 2 | -1 | 0 | -2 | 1 | 0 | ( $R_{x}, R_{y}$ ) |
(a)244
(b)471
(c)480
(d)995
Answer
Answer (as printed): B
Explanation
No explanation was printed for this question.
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