Acta Phys. -Chim. Sin. ›› 2002, Vol. 18 ›› Issue (10): 947-951.doi: 10.3866/PKU.WHXB20021017

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Low Temperature Heat Capacities and Thermodynamic Functions of Potassium Dichromate

Nan Zhao-Dong;Tan Zhi-Cheng;Sun Li-Xian   

  1. Thermochemistry Laboratory, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023
  • Received:2002-01-18 Revised:2002-04-08 Published:2002-10-15
  • Contact: Tan Zhi-Cheng

Abstract: The molar heat capacities (Cp,m) of crystalline potassium dichromate (K2Cr2O7) were measured with a precision automated adiabatic calorimeter over the temperature range from 100 K to 390 K. No phase transition or other thermal anomaly was observed in this temperature region. However, it was found that the relationship of Cp,m with respect to temperature T is different in different temperature regions. The polynomial functions of Cp,m vs. T were established in different temperature regions based on the heat capacity measurements by means of the least-fitting square method. These functions are as following: for 100 K ≤ T ≤ 275 K, Cp,m=0.0050T2-1.0320T+125.22 (J•K-1•mol-1);for 275 K ≤ T ≤ 350 K, Cp,m=209.37 J•K-1•mol-1;for 350 K ≤ T ≤390 K, Cp,m=0.0266T2-18.823T+3542.3 J•K-1•mol-1.According to the relationship of Cp,m vs. T and thermodynamic equations, the values of thermodynamic function of potassium dichromate were calculated in the temperature range of 298.15~400.15 K with 5 K intervals.

Key words: Potassium dichromate (K2Cr2O7), Low-temperature heat capacity, Thermodynamic function, Adiabatic calorimetry