Chapter 11 Gas Laws

Elements that exist as gases at 250C and 1 atmosphere

Physical Characteristics of Gases Gases assume the volume and shape of their containers. Gases are the most compressible state of matter. Gases will mix evenly and completely when confined to the same container. Gases have much lower densities than liquids and solids.

The weight of the air (gas molecules) pushing down on Earth Force Area Barometer What is Pressure? Pressure = The weight of the air (gas molecules) pushing down on Earth Pressure is Measured in Units of: Pascals (Pa), millimeters of mercury, (mmHg), torr (torr), atmosphere (atm), and pounds of square inch (psi)

STP- Standard Temperature and Pressure To compare volumes of gases, one must know temperature and pressure at which the volumes are measured. Scientists have agreed upon standards conditions of exactly 1 atm pressure and 0 degrees celsius (273K).

1 atmosphere of pressure = 760 mmHg Under STP: 1 atmosphere of pressure = 760 mmHg 1atm = 760 torr 1 atm = 101.325kPa 1atm = 14.7psi

The average atmospheric pressure at sea level is 1 atm The average atmospheric pressure at sea level is 1 atm. Basically the weight of air at sea level is equal to 1 atm. What happens to atm pressure as you move further away from sea level? 10 miles 0.2 atm 4 miles 0.5 atm Sea level 1 atm

A Torricellian barometer (sometimes called a mercury barometer) is an inverted (upside-down) glass tube standing in a bath of mercury. Air pressure pushes down on the surface of the mercury, making some rise up the tube. The greater the air pressure, the higher the mercury rises

Convert Units of Pressure: Example #1: Express 0.830 atm in units of mmHg and kPa 0.830 atm x 760 mmHg = 631 mmHg 1 atm 0.830 atm x 101.325 kPa = 84.1 kPa 1 atm

Dalton’s Law of Partial Pressures In a mixture of gases, the total pressure is calculated by adding the pressure of each individual gas in the mixture. V and T are constant P1 P2 Ptotal = P1 + P2

Classwork Page 367 #’s 1-6 *Appendix A8 is on page 859

KEY Pg. 367 #1-6 1. Force / Area 2. mmHg, torr, kPa, psi, atm 3. STP = 273K and 1 atm 4. a) 151.98 kPa x 1 atm = 1.5003 atm 101.3kPa b) 456 torr x 1 atm = 6.00 x 10-1 atm 760 torr Ptotal = 785 mmHg, PH2O = 21.1 mmHg of 21.1 torr ( 1mmHg is equal to 1 torr) Ptotal – PH2O = PN2 785 mmHg – 21.1 mmHg = 764 mmHg 6. The pressure that each gas exerts is independent of thepressues exerted by the other gases.