ANS:C - -1.5

In binary distillation, the q line represents the compositions of the liquid and vapor leaving a stage in terms of mole fractions of the more volatile component. If the feed to the distillation column contains 40 mole % vapor, it means that 40% of the feed is vapor and 60% is liquid. The slope of the q line is given by the equation: Slope of q line=Mole fraction of more volatile component in vaporMole fraction of more volatile component in liquidSlope of q line=Mole fraction of more volatile component in liquidMole fraction of more volatile component in vapor​ Since the feed contains 40 mole % vapor, it means that 40% of the feed is the more volatile component in vapor, and 60% is the more volatile component in liquid. So, the slope of the q line is: Slope=0.40.6=−23Slope=0.60.4​=−32​ Thus, the slope of the q line is -0.6. So, the correct answer is: -0.6