Vid review gases KMT

1. Vid review gases KMT

2. IV. Pressure ---- • A. the amount of Force/area covered. • 1. caused by the collisions between the gas molecules & the container • 2. more pressure doesn’t mean more force • 3. more pressure means the same F covers a smaller area [P = F/area]

3. 4. pressure is measured in: *pascals (Pa) N/m2*** in SI (or kilopascals—kPa) *English system : mm Hg, 1 mm Hg = 1 torr pounds/in2

4. STP • *at sea level & 0oC (this is STP or Standard Temp & Pressure) • atmospheric pressure is: • 1 atm = 760mm Hg • 1 atm = 760 torr • 1 atm = 1.013 x 105 Pa • 1 atm = 101.325 kPa • 1 atm = 14 psi • You will be expected to convert between units! 

5. B. atmospheric pressure measured with a Barometer created by Torricelli in the 1600’s

6. 1. Why can water pumps only raise water to about 34 feet? • 2. He hypothesized that it had to do w/ the weight of the water & the weight of the air. • 3. Said if that’s the case then mercury which is 14 times more dense than water should only be able to be raised to 1/14 of the same height.

7. 4. TRUE! • 5. took a test tube full of mercury, put his thumb over the end, up-ended it in a pan of mercury, it rose/dropped to 760mm height (a little over 2 ft) • 6. He repeated the experiment changing variables such as diameter & length of tube of mercury…..results were always the same!

8. 7. The mercury in the tube is pulled down due to gravity… • when the force of gravity = the force of the air pressing down on the mercury in the pan the column of Hg stops dropping. • 8. If the amount of air pressure changes…the height of the mercury changes!

9. Properties of Gases V = volume of the gas (liters, L) T = temperature (Kelvin, K) P = pressure (atmospheres, atm) n = amount (moles, mol) Gas properties can be modeled using math. Model depends on:

10. V. Gas Laws- A. Boyle’s Law • A. Boyle’s Law 1662–relates vol. & pressure---volume of a fixed mass of gas is inversely proportional to the pressure at a constant temp.---- • so when the volume goes up the pressure goes down (at constant temp) & vice versa V2 = V1P1 or P1V1 = P2V2 P2 *usually Volume 1 is initial & volume 2 is final p.315

11. Boyle's Law This means, for example, that Pressure goes up as Volume goes down. A bicycle pump is a good example of Boyle's law. As the volume of the air trapped in the pump is reduced, its pressure goes up, and air is forced into the tire. Robert Boyle (1627 - 1691) Son of Early of Cork, Ireland.

12. Changing the Size of the Container • In a smaller container - molecules have less room to move. • They hit the sides of the container more often. • This causes an increase in pressure. • As volume decreases: pressure increases.

13. Mechanics of Breathing Timberlake, Chemistry 7th Edition, page 254

14. Exchange of Blood Gases Timberlake, Chemistry 7th Edition, page 273

15. SCUBA Diving • Self Contained Underwater Breathing Apparatus • Rapid rise causes “the bends” • Nitrogen bubbles out of blood rapidly from pressure decrease Must rise slowly to the surface to avoid the “bends”.

16. PV Calculation (Boyle’s Law) A quantity of gas has a volume of 120 L when confined under a pressure of 93.3 kPa at a temperature of 20 oC. At what pressure will the volume of the gas be 30 L at 20 oC? P1 x V1 = P2 x V2 (93.3 kPa) x (120L) = (P2) x (30L) P2 = 373.2 kPa