CHEMISTRY · Single correct · AP · Chemistry · Properties of Substances and Mixtures · Properties of Substances and Mixtures
Problem
A beaker of ethanol is warmed from 20 °C to 40 °C. Which statement best accounts for the observed increase in the rate of evaporation in terms of the molecular speed distribution?
(a) Heating narrows the speed distribution, so collisions become less frequent and molecules leave more easily.
(b) Raising the temperature weakens hydrogen bonding so much that molecular speed becomes irrelevant; molecules escape mainly because intermolecular forces disappear.
(c) At the higher temperature, a larger fraction of molecules possess sufficient kinetic energy to overcome intermolecular attractions at the liquid surface.
(d) The total kinetic energy of every ethanol molecule doubles, allowing all molecules to escape the surface.