1 化学英语证书考试（PEC）-化工热力学常用术语Absolute entropyis entropy calculated relative to the absolute reference point determined by the third law of thermodynamics. Clausius inequalityfirst stated by the German physicist R. J. E. Clausius (1822-1888), is expressed as the cyclic integral of Q/T is always less than or equal to zero. This inequality is valid for all cycles, reversible or irreversible. Entropy(from a classical thermodynamics point of view) is a property designated S and is defined as dS =(dQ/T)int rev. Entropy(from a statistical thermodynamics point of view) can be viewed as a measure of molecular disorder, or molecular randomness. The entropy of a system is related to the total number of possible microscopic states of that system, called thermodynamic probability p, by the Boltzmann relation , expressed as S = k ln pwhere k is the Boltzmann constant. Entropy balance relation for a control volumeis stated as the rate of entropy change within the control volume during a process is equal to the sum of the rate of entropy transfer through the control volume boundary by heat transfer, the net rate of entropy transfer into the control volume by mass flow, and the rate of entropy generation within the boundaries of the control volume as a result of irreversibilities. Entropy balance relation in generalis stated as the entropy change of a system during a process is equal to the net entropy transfer through the system boundary and the entropy generated within the system as a result of irreversibilities. Entropy change of a closed systemis due to the entropy transfer accompanying heat transfer and the entropy generation within the system boundaries. Entropy generationSgen is entropy generat...
