The hydrogen chloride (HCl) molecule has an internuclear separation of 127 pm (picometers). Assume the atomic isotopes that make up the molecule are hydrogen-1 (protium) and chlorine-35. (a) Find the energy of the third excited rotational state; that is, the J

the energy of the third excited rotational state

Explanation:

Given that :

hydrogen chloride (HCl) molecule has an intermolecular separation of 127 pm

Assume the atomic isotopes that make up the molecule are hydrogen-1 (protium) and chlorine-35.

Thus; the reduced mass μ =

μ =

μ =

∵ 1 μ = 1.66 × 10⁻²⁷ kg

μ  =

μ  = 1.6139 × 10⁻²⁷ kg

The rotational level Energy can be expressed by the equation:

where ;

J = 3 ( i.e third excited state)  &

We know that :

1 J =

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