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AP Notes Chapter 11. Properties Of Gases. Temperature. An indirect measure of the average kinetic energy of a collection of particles KE avg = kT Boltzman Plot. Pressure.
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AP Notes Chapter 11 Properties Of Gases
Temperature • An indirect measure of the average kinetic energy of a collection of particles KEavg = kT Boltzman Plot
Pressure Measure of the number of collisions between gas particles and a unit area of the wall of the containerPressure = force / unit area
Force/area English system: pounds/in2 (psi) Metric system: Newton/m2 (pascal)
Torricelli Barometer h = 760 mm Hg 1 atmosphere pressure
1 atm = 760 torr (mm Hg) = 101.325 kPa = 1.01325 bar =14.70 psi
Patm Manometer h Pgas
Patm Manometer h Pgas
Volume Total space of a container that gases occupy due to the free random motion of the gas molecules
V P (at constant T)
Slope = k V 1/P (at constant T)
In mathematical terms: y = mx + b Boyle’s Law
In mathematical terms: y = mx + b V = mT + b Charles’ Law
Where T must be in Kelvin (K) temperature K = 0C + 273
In mathematical terms: y = mx + b P = mT + b Gay-Lussac’s Law
Relationship between Volume & Moles of Gases V-n
In mathematical terms: y = mx + b V = mn + b Avogadro’s Law
Avogadro’s Hypothesis At constant temperature and pressure, equal volumes of gases contain equal number of particles
3. Hydrogen gas [8.3 liters] reacts in the presence of 2.5 liters of nitrogen gas at 370C and 100 kPa. What volume of ammonia is produced at these same conditions?
Ideal & Real Gasses
Kinetic Molecular Theory 1. Gases consist of small particles that are far apart in comparison to their own size. These particles are considered to be tiny points occupying a negligible volume compared to that of their container.
Kinetic Molecular Theory 2. Molecules are in rapid and random straight-line motion. This motion can be described by well-defined and established laws of motion.
Kinetic Molecular Theory 3. The collisions of molecules with the walls of a container or with other molecules are perfectly elastic. That is, no loss of energy occurs.
Kinetic Molecular Theory 4. There are no attractive forces between molecules or between molecules and the walls with which they collide.
Kinetic Molecular Theory 5. At any particular instant, the molecules in a given sample of gas do not all possess the same amount of energy.
PARTICLE IN THE BOX Have 1 particle, with mass m, with velocity
But: f = ?
But: f = ma where
Change in velocity = (
But, and, the distance a particle travels between collisions with the same wall is ?
Substituting into we get:
This represents the pressure (P) that one particle exerts striking opposite walls in the box.
Now assume the box contains N particles. Then, N/3 particles are traveling between opposite walls.
Thus, the total pressure on opposite walls is: