Given:

= 1.29

Formula used:

… (i),

where

γ = ratio of molar heat capacities at constant pressure to constant volume

f = number of degrees of freedom

(i) becomes :

=> … (ii)

Substituting γ = 1.29 in (ii), we get

f = = 6.89 which is approximately equal to 7.

Thus, the number of degrees of freedom is approximately equal to 7.