1. Gases

2. Pressure Properties of Gases Gases uniformly fill any container
Gases are easily compressed
Gases mix completely with any other gas
Gases exert pressure on their surroundings

3. Pressure Measuring barometric pressure The barometer Units
Invented by Evangelista Torricelli in 1643
Units
mm Hg (torr) torr = 1 atm
newtons/m2 (pascal (Pa)) ,325 Pa = 1 atm
101,325 Pa = kPa
Atmospheres atm = standard
pressure

4. The Gas Laws of Boyle, Charles and Avogadro
Boyle’s law (Robert Boyle)
The product of pressure times volume is a constant, provided the temperature and number of moles remains the same
Pressure and volume are inversely related
Volume increases linearly as the pressure decreases (1/P)

5. The Gas Laws of Boyle, Charles and Avogadro
Boyle’s Law Continued……
At constant temperature, Boyle’s Law can be used to find a new volume or pressure
Boyle’s law works best at low pressures
Gases that obey Boyle’s Law are called Ideal Gases

6. The Gas Laws of Boyle, Charles and Avogadro
Charles’ Law (Jacques Charles)
The volume of a gas increases linearly with temperature provided the pressure and number of moles remain constant.
Temperature and volume are directly proportional

7. The Gas Laws of Boyle, Charles and Avogadro
Charles’ Law continued………..
Temperature must be measured in degrees Kelvin
K = oC + 273
0 K is “absolute zero”

8. The Gas Laws of Boyle, Charles and Avogadro
Avogadro’s Law (Amedeo Avogadro) For a gas at constant temperature and pressure, the volume is directly proportional to the number of moles.

9. Combined gas law – (n remaining constant)
The Combined Gas Law
Combined gas law – (n remaining constant)

10. The Ideal Gas Law Derived from existing laws…….
V = k/P, V = bT and V = an
V = (k)(b)(a)(Tn/P)
Constants k, b and a are combined into the universal gas constant R and…..

11. The Ideal Gas Law Limitations of the Ideal Gas Law
Works well at low pressure and high temperatures
Most gases do not behave ideally above 1 atm
Does not work well near the condensation conditions of a gas

12. Variations of the Ideal Gas Law
Density Molar Mass of a gas

13. Dalton’s Law of Partial Pressure
“For a mixture of gases in a container, the total pressure exerted is the sum of the pressures each gas would exert if it were alone.” It is the total number of moles that is important, not the identity or composition of the gas particles.

14. gas stoichiometry
At Standard Temperature and Pressure (STP) T = K (0oC) P = 1 atm (760 torr or kPa) 1 mole of an ideal gas occupies 22.4 L of volume Remember…….. Density = mass/volume and moles (n)= grams/molar mass