Author(s):
1. Mitar Perušić, Tehnološki fakultet u Istočnom Sarajevu, Republic of Srpska, Bosnia and Herzegovina
2. Branko Pejović, Tehnološki fakultet u Istočnom Sarajevu, Republic of Srpska, Bosnia and Herzegovina
3. Stefan Pavlović, Tehnološki fakultet u Istočnom Sarajevu, Republic of Srpska, Bosnia and Herzegovina
4. Dragana Kešelj, Republic of Srpska, Bosnia and Herzegovina
5. Radislav Filipovic, Tehnološki fakultet u Istočnom Sarajevu, Republic of Srpska, Bosnia and Herzegovina

Abstract:
The paper is based on the fact that the internal energy, enthalpy and entropy as the most important thermodynamic state functions, can not be determined in absolute terms without reference state selections. It is demonstrated that to this determination must be approached very cautiously. The reason for this is the possibility of errors that are not permissible. The beginning conditions of the measurement can be adopted. It is also necessary to pay attention to the beginnig of the measurement of the adopted reference value. For a case to be made simultaneous determination of multiple state funtions, it should take to account of the beginning of the measurement of each of these functions, since this start may be different. In this way the calculated state function varies, depending on which reference state is adopted. At the end, in one convenient example, in the case of internal energy and enthalpy, as a characteristic state function, is pointed to the possibility of errors, which could occur if there is no detailed analysis of adopted reference or "zero" state.

Key words:
enthalpy,entropy,ideal gas.

Thematic field:
Chemical Engineering

Date of abstract submission:
14.07.2016.

Conference:
XI Savjetovanje hemičara, tehnologa i ekologa Republike Srpske

Final paper