You are interested in finding the pressure at which the first bubble of vapor will form from a liquid mixture of methanol (1) and 2-methyl1-propanol (2) (49% by mole methanol) at 508C. The Margules parameters for this mixture are A12 5 0.2565 and A21 5 0.2404 (Gmehling and Onken, 1977). Note that the vapor pressure of methanol is 422 mm Hg and that for 2-methyl-1-propanol is 56 mm Hg at 508C. Find the pressure and vapor-phase composition.

both adhesion and cohesion are attractions.

they are different in that adhesion is the force of attraction between the molecules of two different substances, whereas cohesion is the force of attraction between molecules of the same substance.

possible examples include capillary action, in which the adhesion between water and glass causes the water to rise in a narrow tube against the force of gravity.

because of hydrogen bonding, water is extremely cohesive.

this causes molecules on the surface of water to be drawn inward, which is why drops of water form beads on smooth surfaces.

hope this .

answer : a model is often used to explain and make things easier to understand when any scientific topic needs to be demonstrated and explained.

as in this case where a scientist wants to use a model to present the results of his detailed scientific investigation. he should do it as it will him to make the audience understand the concept in a much better way. also, it can be changed according to new scientific understandings.