# Working with molecules in first excited rotational state

Calculate the ratio of HCL molecules in the first excited rotational state to those in the ground state @ 25 C. Assume an equilibrium bond distance of 1.275 angstroms.

the angstrom part of the problem throws me off, I usually start these out by solving Change in E = ( h ) ( c )(Wo), but this is a q (rot) prob, not a q (elec). how do i solve this ?

© BrainMass Inc. brainmass.com October 9, 2019, 5:10 pm ad1c9bdddfhttps://brainmass.com/chemistry/general-chemistry/working-molecules-first-excited-rotational-state-49904

#### Solution Preview

If we have No molecules in the gnd state and Nj atoms in the excited state, , the boltzmann distribution tells us that,

Nj/No = Exp[-Ej/kT]

where K = 1.38*10^-23, the Boltzmann's constant, T is the absolute temperature and Ej is given by,

Ej = BhC J(J+1)

where h = 6.63*10^-34 JS, the Planks constant

C the velocity of licht in cm/second

and B is the rotational ...

#### Solution Summary

The solution provides and easy to follow explanation of the concepts and gives all mathematical steps wherever necessary.