The gas-liquid equilibrium for a component is described by the equation y = 2.5x. The measured mole fractions in a packed column are 0.3 in the liquid phase and 0.4 in the gas phase. What is the type of separation operation? If the gas side mass transfer coefficient is two times the liquid side mass transfer coefficient, what are the interfacial concentrations?

Sounds like homework...

I google (https://www.google.com)'d "interfacial concentration" and found this (http://dragon.unideb.hu/~kolloid/colloid/lectures/chembsc/lecture%2003.pdf). Poking around some more, this (https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=5&ved=0ahUKEwiuyNTc2enJAhUJOiYKHcDWDwUQFgg8MAQ&url=http%3A%2F%2Fwww.kau.edu.sa%2FFiles%2F0008595% 2FFiles%2F59993_Lecture%25206.ppt&usg=AFQjCNF99fM-fcED3xDHO_byi7-GJcrkqQ&sig2=Z52ZOyKlH0DpNyJWBUcfNQ&cad=rja)

What have you got for answers, I'm sure someone here can guide you along the right path.