List of top Physical Chemistry Questions on Spectroscopy

Among the following, the one for which the infrared active vibrational modes are Raman inactive and vice versa is

A 0.005 M solution of compound X transmits 80% of the incident light of wavelength ($\lambda$) 500 nm. The absorbance of 0.01 M solution of X is (rounded off to three decimal places).
(Given: path length = 1.0 cm)

The rotational spectrum of HF has equally spaced lines that are 40.9 cm$^{-1}$ apartThe moment of inertia of HF is $Y \times 10^{-47}$ kg m$^2$The value of Y is _ _ _. (rounded off to three decimal places)

The number of normal modes of vibration in benzene is _ _ _. (answer in integer)

The wavelength of the γ-ray emitted in

is _______ Å. (rounded off to three decimal places)
[Given: h=6.626×10⁻³⁴ J s; c=2.998×10⁸ m s⁻¹ ; 1 MeV=1.602×10⁻¹³ J]

If 1 M of a dye in water transmits 50% of incident light at 400 nm, then 2 M of the dye in water transmits _______ % of the incident light at 400 nm. (rounded off to the nearest integer)
[Given: Both experiments are performed in the same spectrophotometric cell.]

For the following compound

compound-signals expected in the 1H NMR spectrum

the number of signals expected in the 1H NMR spectrum is _________.

The stretching frequency of CO in H₃B.CO is

A 0.06 g/mL solution of (S)-1-phenylethanol placed in a 5 cm long polarimeter tube shows an optical rotation of 1.2^o . The specific rotation is ______ ^o .
(round off to the nearest integer)

The highest possible energy of a photon in the emission spectrum of hydrogen atom is ______ eV.
[Given: Rydberg constant = 13.61 eV]
(round off to two decimal places)

The number of singlets observed in the 1H NMR spectrum of P is ____.

The harmonic vibrational frequency of a diatomic molecule is 2000 cm⁻¹ . Its zero point energy is eV.
[Given: Planck’s constant = 6.62x10⁻³⁴ J s; 1 eV = 1.6x10⁻¹⁹ J]
(round off to two decimal places)

The spacing between successive rotational energy levels of a diatomic molecule XY and its heavier isotopic analogue X'Y' varies with the rotational quantum number, J, as

The number of CO stretching bands in the infrared spectrum of $Fe(CO)_5$ is

The number of signals observed in the $^1H NMR$ spectrum of the compound

is _________.

Two close lying bands in a UV spectrum occur at 274 nm and 269 nm. The magnitude of the energy gap between the two bands is ____cm^-1. (round off to the nearest integer)

At a certain wavelength, liquid P transmits 70%, whereas liquid Q transmits 30% of the incident light when separately placed in a spectrophotometric cell (path length = 1 cm). In a binary mixture of liquids P and Q (assume non-interacting liquids), the absorbance in the same cell is 0.25. The volume fraction of liquid P in the binary mixture is .......... (Round off to two decimal places)

The compound(s) which will have only two signals in the $ ^1 \text{H} $ NMR spectrum in 3:2 ratio is(are)

The boron adduct(s), which show(s) three signals in $ ^1 \text{H} $ NMR spectrum with the intensity ratio 1:2:3 is(are)

The force constant for H$^{35}$Cl and D$^{35}$Cl are the same and both can be considered as harmonic oscillators. H$^{35}$Cl has a fundamental vibrational transition at 2886 cm$^{-1}$. The ratio of the zero-point energy of H$^{35}$Cl to that of D$^{35}$Cl is

The CORRECT order of carbonyl stretching frequencies for the following compounds is

Among the following hydrocarbon(s), how many of them would give rise to three groups of proton NMR peaks with 2:2:3 integration ratio?

The magnitude of crystal field stabilization energy (CFSE) of octahedral $ \text{[Ti(H}_2\text{O)}_6]^{3+} $ complex is 7680 cm$^{-1}$. The wavelength at the maximum absorption ($ \lambda_{\text{max}} $) of this complex is ............ nm (rounded up to the nearest integer).

For $ \text{H}_2 $ molecule, the fundamental vibrational frequency $ \nu_e $ can be taken as 4400 cm$^{-1}$. The zero-point energy of the molecule is ................ kJ/mol (rounded up to two decimal places).
\[\left[ h = 6.6 \times 10^{-34}\,\mathrm{J\,s}, \; c = 3 \times 10^{8}\,\mathrm{m\,s^{-1}}, \; N_A = 6 \times 10^{23}\,\mathrm{mol^{-1}} \right]\]