Question

1. Which of the following is not true about K-values:

   		Historically, K-values for light hydrocarbons were often taken from a set of charts constructed by DePriester, hence called DePriester charts.
   		K=0.5 when an azeotrope exists at the given temperature.
   		The K-value is a convenient construct for use in flash calculations.
   		When Raoult’s law can be applied, the K-values are constant.

Answer 1

The VLE 's are eaisly defined in terms of K value ,which is distribution coefficient ,under ideal conditions Rault's and Dalton's law both apply ,hence k =y_i/x_{i =} p_i/$\prod$, however for pressure above 30 psi this equation was not valid and hence a new term of fugacity was introduced ,which all simplified the value of K using graph as a function on temperature and pressure

k= f_il/f_iv {fugacity in liquid  to vapor phase }

Various charts are derived to study the K value once such is kellog"s chart, it was used by de priester to study hydrocarbons ,

similarly k values are convenient to construct flash calculations , however for azeotrope mixture k value should be equal to 1 as in azeotrope the gaseous and liquid phase composition are equal , hence the wrong statement is 2 number .