90 likes | 157 Views
Theory. (KMT). Kinetic Molecular. of Gases. KE = ½ mv 2. Kinetic Molecular Theory of Gases.
E N D
Theory (KMT) Kinetic Molecular of Gases
KE = ½ mv2 Kinetic Molecular Theory of Gases • A gas is composed of molecules that are separated from each other by distances far greater than their own dimensions. The molecules can be considered to be points; that is, they possess mass but have negligible volume. • Gas molecules are in constant motion in random directions, and they frequently collide with one another. Collisions among molecules are perfectly elastic. • Gas molecules exert neither attractive nor repulsive forces on one another. • The average kinetic energy of the molecules is proportional to the temperature of the gas in kelvins. Any two gases at the same temperature will have the same average kinetic energy
Kinetic theory of gases and … • Compressibility of Gases • Boyle’s Law • Pa collision rate with wall • Collision rate a number density • Number density a 1/V • Pa 1/V • Charles’ Law • Pa collision rate with wall • Collision rate a average kinetic energy of gas molecules • Average kinetic energy aT • PaT
Kinetic theory of gases and … • Avogadro’s Law • Pa collision rate with wall • Collision rate a number density • Number density an • Pan • Dalton’s Law of Partial Pressures • Molecules do not attract or repel one another • P exerted by one type of molecule is unaffected by the presence of another gas • Ptotal = SPi
KE KE KE KE KE KE KE KE KE KE KE KE KE KE KE Kinetic theory of gases and … • Temperature is a value that is proportional to the average kinetic energy of the particles in the sample. The key word here is AVERAGE. Some of the particles have a very small KE while others have a very large KE. Most are somewhere in the middle of the group near the “average” KE LINK TO SIMULATION Click Here
The distribution of speeds of three different gases at the same temperature The distribution of speeds for nitrogen gas molecules at three different temperatures LINK TO SIMULATION Click Here
So why is it called the IDEAL gas law? n = = 1.0 PV RT Because real gases deviate from ideal behavior How? Real gases attract & repel each other and take up space Why? Do you remember dipole-dipole interactions, hydrogen bonding, and London dispersion forces? 1 mole of ideal gas PV = nRT Repulsive Forces Attractive Forces
Effect of intermolecular forces on the pressure exerted by a gas.
Effect of individual particle volume on the total volume occupied by a real gas. Real gases however, do actually take up some of the space and the “available” space for them to move is less than that of the container. With PV=nRT we assume the particles themselves do not take up any of the space so we set the value of V = to the volume of the container.