# Which of the following vibrational modes of CO2 is doubly degenerate?

## Which of the following vibrational modes of CO2 is doubly degenerate?

symmetric stretching

Hear this out loudPauseThe CO2 molecule has three normal modes of vibration: symmetric stretching, bending (which is doubly degenerate) and antisymmetric stretching.

## Does CO2 have two degenerate bending modes of vibration?

Hear this out loudPauseThe four normal modes of carbon dioxide, Figure 1, are the symmetric stretch, the asymmetric stretch and two bending modes. The two bending modes have the same energy and differ only in the direction of the bending motion. Modes that have the same energy are called degenerate.

**How many vibrational modes does h2o2 have?**

six

Hear this out loudPause. A complete vibrational analysis is worked out for hydrogen peroxide, using the data of Giguere & Bain. The FG matrix method of Howard & Wilson is employed, use being made of symmetry co-ordinates. The amplitude factors corresponding to each of the six normal modes of vibration are calculated.

### What are degenerate modes of vibration?

Hear this out loudPauseEach mode has a definite frequency of vibration. Sometimes 2 or 3 modes may have the same frequency but that does not change the fact that they are distinct modes; these modes are called degenerate. Sometimes some modes are not IR active but they exist all the same.

### What are the two vibrational modes?

Hear this out loudPauseThe vibrational modes can be IR or Raman active.

**Which vibrations of CO2 are not IR active?**

Hear this out loudPauseFor CO2 (linear molecule) there are 4 vibrational modes corresponding to symmetric stretch, antisymmetric stretch and two bends. The symmetric stretch does not change the dipole moment so it is not IR active.

## How do you determine if a vibrational modes IR active?

Hear this out loudPauseIn order to determine which modes are IR active, a simple check of the irreducible representation that corresponds to x,y and z and a cross check with the reducible representation Γvib is necessary. If they contain the same irreducible representation, the mode is IR active.

## What vibrational modes are IR active?

Hear this out loudPauseIf a vibration results in the change in the molecular dipole moment, it is IR-active. In the character table, we can recognize the vibrational modes that are IR-active by those with symmetry of the x,y, and z axes. In C2v, any vibrations with A1, B1 or B2 symmetry would be IR-active.

**How many vibrational modes does CO2 have?**

Linear triatomic molecules such as CO2 and CS2 have four vibrational normal modes but just three fundamental vibration frequencies because two modes are degenerate. 1 The stretching mode is totally symmetric so it is inactive in infrared spectra and active in Raman spectra.

### How are the vibration frequencies of CS2 calculated?

A Fermi resonance in the Raman spectrum will be interpreted in terms of interacting normal modes. Vibration frequencies will be calculated with ab initioquantum-chemical methods and compared to experimental frequencies. CS2has longer bonds and lower vibration frequencies than CO2. Introduction

### How is the number of vibrational normal modes determined?

The number of vibrational normal modes can be determined for any molecule from the formula given above. For a diatomic molecule, N = 2 so the number of modes is 3 × 2 − 5 = 1. For a triatomic linear molecule (CO 2 ), it is 3 × 3 − 5 = 4 and triatomic nonlinear molecule (H 2 O), it is 3 × 3 − 6 = 3 and so on.

**How to calculate the vibrational energy of H 2 O?**

Calculate the vibrational energy in Joules per mole of a normal mode in question 3, in its ground state of n = 0. Assuming the force constant to be the same for H 2 O and D 2 O. A normal mode for H 2 O is at 3650 c m − 1.