KMT

KMT Postulate 1

Gas molecules are separated by distances far greater than their own dimensions; they have mass but negligible volume and are treated as points

KMT Postulate 2

Gas molecules are in constant, random motion and frequently collide with one another; all collisions are perfectly elastic

KMT Postulate 3

Gas molecules exert neither attractive nor repulsive forces on one another

KMT Postulate 4

The average kinetic energy of molecules is proportional to the temperature of the gas in Kelvins; any two gases at the same temperature have the same average kinetic energy

Boyle's Law (KMT explanation)

Decreasing volume causes molecules to collide with container walls more frequently, increasing pressure

Charles's Law (KMT explanation)

Increasing temperature causes molecules to move faster; at constant pressure, volume increases to compensate for increased molecular motion

Gay-Lussac's Law (KMT explanation)

Increasing temperature causes molecules to move faster; at constant volume, this results in increased pressure

Avogadro's Law (KMT explanation)

Increasing the number of particles at constant temperature and pressure increases collisions, so volume increases to compensate

Intermolecular Forces Effect on Pressure

A molecule near the container wall is pulled back toward the interior by neighboring molecules, reducing its impact force and lowering the measured pressure below the ideal value

Nonideal Gas Behavior Conditions

Gases deviate most from ideal behavior at low temperature AND high pressure; low temperature allows intermolecular attractions to become significant as molecules move slowly, while high pressure forces molecules close enough together that their own volume becomes significant

Van der Waals Equation

(P + an²/V²)(V

Van der Waals Pressure Correction (an²/V²)

Accounts for the probability that molecules will be close enough to experience intermolecular attraction, which reduces pressure

Van der Waals Volume Correction (nb)

Accounts for the fact that gas molecules, while very small, do occupy some finite volume

Gas with Weakest Intermolecular Attraction

Helium (He); it has the lowest van der Waals constant a = 0.034 atm·L²/mol²