Answer to Question #129069 in Molecular Physics | Thermodynamics for shiras

Question

A vessel contains non, linear triatomic gas. If y
fraction of gas dissociate into individual atom then
new value of degree of freedom will be (ignoring
vibrational mode)

Answer 1

In general, non-linear molecule(with N atoms) has 3 translational, 3 rotational and 3N-6 vibrational degrees of freedom. If we ignore vibrational degrees of freedom we have 6 degrees of freedom left. Single atom molecule has only 3 translational degrees of freedom. Thus, if y fraction of gas molecules will dissociate (releasing 3 atoms each) we will have 6(1-y) + 9y = 6 + 3y degrees of freedom.