The statistical thermodynamic model for the vibrational partition function with separated stretching and bending is developed. The model is studied on the example of CO2molecule for temperature up to 20,000 K with the aim to describe efficient dissociation by deposition of energy mainly to the stretching modes of vibration. The observed separation of bending mode at lower temperatures suggest that it is possible to construct such kinetic model of plasma in which the high vibrational temperature of stretching and the low vibrational temperature of bending are obtained resulting in an efficient dissociation. In particular, the proposed model is extended to ideal-gas version where all the interactions between atoms are taken into account. The idea behind such approach is to eliminate contributions to partition functions stemming from non-interacting dissociated fragments of the molecule. The application areas of such partition functions are discussed and the full vibrational partition functions based on that model are compared with the known data.