Excess property

<p>In <a href="/facts/Chemical_thermodynamics/dIQMQsd0">chemical thermodynamics</a>, excess properties are <a href="/facts/List_of_thermodynamic_properties/d4Kzdqy8">properties</a> of <a href="/facts/Mixture/tms8rbmn">mixtures</a> which quantify the non-<a href="/facts/Idealization_(philosophy_of_science)/5LVmNhz0">ideal behavior</a> of real mixtures. They are defined as the difference between the value of the property in a real mixture and the value that would exist in an <a href="/facts/Ideal_solution/Ho6rPlcs">ideal solution</a> under the same conditions. The most frequently used excess properties are the excess <a href="/facts/Volume/aeAXCBUd">volume</a>, excess <a href="/facts/Enthalpy/bBou8lCE">enthalpy</a>, and <a href="/facts/Excess_chemical_potential/RSC2yjps">excess chemical potential</a>. The excess volume (VE), <a href="/facts/Internal_energy/IYdsoxhR">internal energy</a> (UE), and enthalpy (HE) are identical to the corresponding mixing properties; that is,
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V
                  
                    E
                  
                
              
              
                
                =
                Δ
                
                  V
                  
                    mix
                  
                
              
            
            
              
                
                  H
                  
                    E
                  
                
              
              
                
                =
                Δ
                
                  H
                  
                    mix
                  
                
              
            
            
              
                
                  U
                  
                    E
                  
                
              
              
                
                =
                Δ
                
                  U
                  
                    mix
                  
                
              
            
          
        
      
    
    {\displaystyle {\begin{aligned}V^{E}&=\Delta V_{\text{mix}}\\H^{E}&=\Delta H_{\text{mix}}\\U^{E}&=\Delta U_{\text{mix}}\end{aligned}}}

<p>These relationships hold because the volume, internal energy, and enthalpy changes of mixing are zero for an ideal solution.
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Excess property open-in-new

Excess property