Question

PLEASE ANSWER CLEARLY WITH WORK SHOWN WILL GIVE 5 STARS!!

As the temperature of a liquid increases, its vapor pressure ncreases. The hotter the liquid, the faster it evaporates. When the vapor pressure equals the external (atmospheric) pressure, the liquid boils.

A. Explain in detail using the principles of kinetic molecular theory why the entire remaining sample of the liquid does no vaporize all at once at the instant the boiling point is reached.

B.Calculate the amount of energy needed to vaporize 15.0 mL of water. Show work clearly. Identify all terms used. Include all units.

Answer 1

A) when the boiling point is reached, the molecules in the liquid will collide with each other very erratically. so molecules gain mass times velocity(momentum) and escape out of the liquid surface.
but it has to have a trajectory path towards the liquid surface to get it vapourized. at boiling point, due to collisions they follow different path and may approach the walls of the distillation column or the container. so not the whole of liquid escapes at once.
consider this eg.
splash water on a flat surface. they evaporate quickly than the one in a puddle or any hollow container.

B) heat of vapourisation of water= 2330 joule/gram

15 ml or 15 grams of H2O x 2330 J/gram = 34.95 KJ