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Episode I ATTACK OF THE GAS

Not so long ago, in a chemistry lab far far away…. May the FORCE/area be with you. Episode I ATTACK OF THE GAS Gas, being of upmost importance to the entire galaxy and your life, is in constant battle due to the ruthless variations of temperature, pressure, and the amount of particles.

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Episode I ATTACK OF THE GAS

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  1. Not so long ago, in a chemistry lab far far away… May the FORCE/area be with you Episode I ATTACK OF THE GAS Gas, being of upmost importance to the entire galaxy and your life, is in constant battle due to the ruthless variations of temperature, pressure, and the amount of particles. It is imperative that you understand properties of gases and how those ruthless variations affect the gases. You will need to make some minor assumptions to conquer this topic. However, there is certainty that you will prevail…

  2. Gas Laws: Dalton’s LawAt the conclusion of our time together, you should be able to: Explain Dalton’s Law Use Dalton’s Law to solve a problem

  3. Dalton’s Law John Dalton 1766-1844

  4. Dalton’s Law of Partial Pressures • For a mixture of gases in a container, • PTotal = P1 + P2 + P3 + . . . This is particularly useful in calculating the pressure of gases collected over water.

  5. Dalton’s Law of Partial Pressures • 2 H2O2 (l) ---> 2 H2O (g) + O2 (g) • 0.32 atm 0.16 atm What is the total pressure in the flask? Ptotal in gas mixture = PA + PB + ... Therefore, Ptotal = PH2O + PO2 = 0.48 atm Dalton’s Law: total P is sum of PARTIAL pressures.

  6. “Disorder in the American Courts”These are statements people actually said in court, word for word, taken down and now published by court reporters. ATTORNEY:  Were you present when your picture was taken? WITNESS:     Are you shitting me?

  7. Health Note When a scuba diver is several hundred feet under water, the high pressures cause N2 from the tank air to dissolve in the blood. If the diver rises too fast, the dissolved N2 will form bubbles in the blood, a dangerous and painful condition called "the bends". Helium, which is inert, less dense, and does not dissolve in the blood, is mixed with O2 in scuba tanks used for deep descents.

  8. Gases in the Air The % of gases in air Partial pressure (STP) 78.08% N2 593.4 mm Hg 20.95% O2 159.2 mm Hg 0.94% Ar 7.1 mm Hg 0.03% CO2 0.2 mm Hg PAIR = PN + PO + PAr + PCO = 760 mm Hg 2 2 2 Total Pressure = 760 mm Hg

  9. Collecting a gas “over water” • Gases, since they mix with other gases readily, must be collected in an environment where mixing can not occur. The easiest way to do this is under water because water displaces the air. So when a gas is collected “over water”, that means the container is filled with water and the gas is bubbled through the water into the container. Thus, the pressure inside the container is from the gas AND the water vapor. This is where Dalton’s Law of Partial Pressures becomes useful.

  10. Table of Vapor Pressures for Water

  11. Solve This! A student collects some hydrogen gas over water at 20 degrees C and 768 torr. What is the pressure of the H2 gas? 768 torr – 17.5 torr = 750.5 torr

  12. Dalton’s Law of Partial Pressures • Also, for a mixture of gases in a container, because P, V and n are directly proportional if the other gas law variables are kept constant: • nTotal= n1+ n2+ n3+ . . . • VTotal = V1 + V2 + V3 + . . . This is useful in solving problems with differing numbers of moles or volumes of the gases that are mixed together.

  13. Did I ever tell you how much I hate computers!!!

  14. Gas Laws: Dalton’s LawLet’s see if you can: Explain Dalton’s Law Use Dalton’s Law to solve a problem

  15. Dalton’s Law Problems, Page 38:5 Using Dalton’s & Boyle’s Laws (295.0 torr) (3.00 L) (530.0 torr) (1.00 L) 4.00 L (P) 354 torr

  16. Dalton’s Law Problems, Page 39:7 Using Dalton’s & Ideal Gas Laws ((1.00 atm – (17.5 torr x 1 atm/760 torr)) (250.0 L) 0.977 atm(250) (x mol) (0.08206 atm*L/mol*K) (293 K) 10.2 mol N2 x 28.02 g/mol 285 g N2

  17. Surrounded by Engines!!!

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