# Strength of a bond in a molecule

1. Aug 17, 2012

### solas99

1. The problem statement, all variables and given/known data
Carbon monoxide molecule, which has a reduced mass of 6.85 amu, absorbs infrared radiation wavelength of 4.6um. if the absorption is due to vibrational transitions, calculate the strength of the bond in molecule

2. Relevant equations

u=(m1*m2)/(m1+m2)

3. The attempt at a solution

1. (12*16)/(12+16)=6.85 amu= 1.13e-26 Kg

here i calculate the reduced mass...but the reduced mass is given in the question! i just dont know what equation to use to calculate bond strength from wavelength and reduced mass..

there is another equation for frequency of vibrations: v=1/2pi $\sqrt{k/u}$

but i dont know what k stands for? and how we calculate it
is there any other equation im missing?

thank you!

Last edited: Aug 17, 2012
2. Aug 17, 2012

### ehild

k is called the force constant of stretching the bond between carbon and oxygen, and it characterises the stiffness of this bond. Search your notes what was called "the strength of the bond". You can calculate k from the given data. Remember that a vibrating molecule absorbs that radiation which frequency corresponds its vibrational frequency.

ehild

3. Aug 17, 2012

### solas99

E=h(n+1/2)w

4. Aug 18, 2012

### solas99

is k the bond strength?

from equation λ=2pic$\sqrt{u/k}$

do we then solve for K, to give the bond strength?

thanks a mill :)

5. Aug 19, 2012

### ehild

Well, k is not the bond strength, but your book might call it so. Anyway, calculate it.

ehild