Definitions for a multicomponent flash are as follows:

$x_i,y_i=$ liquid and vapor mole fractions, respectively

$z_i,=$ feed mole fraction

$K_i,=\frac{y_i}{x_i}=$ equilibrium constant

$L,V,F=$ liquid, vapor, and feed molar rates

The following function applies when the temperature is known:

$f()={\displaystyle \underset{i}{\overset{?}{}}}\frac{z_i(K_i-1)}{K_i+(1-K_i)}$

where $=\frac{L}{F}.$

The solution for $\frac{L}{F}$ is determined when the function is equal to zero. The behavior of this

function with respect to $,$ between the bubble and dew points, is best described by: