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Bellringer

Bellringer. In the three boxes, draw what the molecules look like in a solid, liquid, and gas. Solid Liquid Gas. GASES. Importance of Gases. Airbags fill with N 2 gas in an accident. Gas is generated by the decomposition of sodium azide, NaN 3 .

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Bellringer

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  1. Bellringer In the three boxes, draw what the molecules look like in a solid, liquid, and gas. Solid Liquid Gas

  2. GASES

  3. Importance of Gases • Airbags fill with N2 gas in an accident. • Gas is generated by the decomposition of sodium azide, NaN3. • 2 NaN3 ---> 2 Na + 3 N2

  4. THREE STATES OF MATTER

  5. Solids • Have a definite shape • Have a definite volume Kinetic Molecular Theory Molecules are held close together and there is very little movement between them.

  6. Liquids • Have an indefinite shape • Have a definite volume Kinetic Molecular Theory: Atoms and molecules have more space between them than a solid does, but less than a gas (ie. It is more “fluid”.)

  7. Gases • Have an indefinite shape • Have an indefinite volume Kinetic Molecular Theory: Molecules are moving in random patterns with varying amounts of distance between the particles.

  8. Kinetic Molecular Model of Water At 100°C, water becomes water vapor, a gas. Molecules can move randomly over large distances. Between 0°C and 100 °C, water is a liquid. In the liquid state, water molecules are close together, but can move about freely. Below 0°C, water solidifies to become ice. In the solid state, water molecules are held together in a rigid structure.

  9. Changing States Changing states requires energy in either the form of heat. Changing states may also be due to the change in pressure in a system.

  10. General Properties of Gases • There is a lot of “free” space in a gas. • Gases can be expanded infinitely. • Gases fill containers uniformly and completely. • Gases diffuse and mix rapidly.

  11. Properties of Gases Gas properties can be modeled using math. Model depends on— • V = volume of the gas (L) • T = temperature (K) • ALL temperatures in the entire chapter MUST be in Kelvin!!! No Exceptions! • n = amount (moles) • P = pressure (atmospheres)

  12. Temperature • T = temperature (K) • ALL temperatures in the entire chapter MUST be in Kelvin!!! No Exceptions! Convert the temperature of this room (23 C) to Kelvin Converting is simple! K = C + 273 C = K - 273

  13. Pause for a Cause Convert the following to Kelvin: Water freezes at 0o C Water boils at 100o C Human Body Temperature is 37o C Convert the following to Celsius: Absolute Zero is 0 K Standard Pressure is 273.15 K

  14. Force Pressure = Area

  15. Pressure • Is caused by the collisions of molecules with the walls of a container is equal to force/unit area. •  SI units = Newton/meter2 = 1 Pascal (Pa) •  1 standard atmosphere (atm) = 101,325 Pa •  1 standard atmosphere (atm) = 760 mm Hg • 1 standard atmosphere (atm) = 760 torrs • 1 standard atmosphere (atm) = 14.7 psi • 1 standard atmosphere (atm) = 101.325 kPa

  16. Pressure Column height measures Pressure of atmosphere • 1 standard atmosphere (atm) * = 760 mm Hg (or torr) * = about 34 feet of water!

  17. 10 miles 0.2 atm 4 miles 0.5 atm Sea level 1 atm 5.2

  18. Pressure Conversions What is 475 mm Hg expressed in atm? 1 atm 760 mm Hg 475 mm Hg x = 0.625 atm

  19. Pressure Conversions A. What is 2 atm expressed in torr?

  20. Pause for a Cause • Convert a pressure of 1.75 atm to kPa and to mm Hg. • Convert a pressure of 570. torr to atmospheres and to kPa. • Convert a pressure of 550 mm of Hg into atm and Pa • Convert a pressure of 150. KPa to mm of Hg and atm

  21. Bellringer – answer in complete sentences 1. If you want to reduce the pressure of gas in a tire, what could you do? 2. As you let the gases in a hair spray can escape, what happens to the volume and pressure of the gas? 3. If you want air to enter your lungs, what must you do to the space inside your chest cavity?

  22. Boyle’s Law P α 1/V This means Pressure and Volume are INVERSELY PROPORTIONAL if moles and temperature are constant (do not change). For example, P goes up as V goes down. P1V1 = P2 V2 Robert Boyle (1627-1691). Son of Early of Cork, Ireland.

  23. Boyle’s Law 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.

  24. Boyle’s Law Problem • A sample of oxygen gas has a volume of 150 mL when its pressure is 0.923 atm. If the pressure is increased to 0.987 atm and the temperature remains constant, what will the new volume be?

  25. You try! • A balloon filled with helium gas has a volume of 500 mL at a pressure of 1 atm. The balloon is released and reaches an altitude of 6.5 km, where the pressure is 0.5 atm. Assuming that the temperature has remained the same, what volume does the gas occupy at this height?

  26. Charles’s Law If n and P are constant, then V α T V and T are directly proportional. V1T2=V2T1 • If the temperature goes up, the volume goes up! Jacques Charles (1746-1823). Isolated boron and studied gases. Balloonist.

  27. Charles’s original balloon Modern long-distance balloon

  28. Charles’s Law

  29. Practice A sample of neon gas occupies a volume of 752 mL at 25°C. What volume will the gas occupy at 50°C if the pressure remains constant?

  30. You try! • A helium-filled balloon has a volume of 2.75 L at 20°C. The volume of the balloon decreases to 2.46 L after it is placed outside on a cold day. What is the outside temperature in K and in °C?

  31. Gay-Lussac’s Law If n and V are constant, then P α T P and T are directly proportional. P1T2= P2T1 • If one temperature goes up, the pressure goes up! Joseph Louis Gay-Lussac (1778-1850)

  32. Practice • The gas in an aerosol can is at a pressure of 3.00 atm at 25°C. Directions on the can warn the user not to keep the can in a place where the temperature exceeds 52°C. What would the gas pressure in the can be at 52°C?

  33. You Try! Before a trip from New York to Boston, the pressure in an automobile tire is 1.8 atm at 20°C. At the end of the trip, the pressure gauge reads 1.9 atms. What is the new Celsius temperature of the air inside the tire?

  34. Combined Gas Law • The good news is that you don’t have to remember all three gas laws! Since they are all related to each other, we can combine them into a single equation. BE SURE YOU KNOW THIS EQUATION! P1 V1 T2 = P2 V2 T1 No, it’s not related to R2D2

  35. Combined Gas Law Problem A sample of helium gas has a volume of 0.180 L, a pressure of 0.800 atm and a temperature of 29°C. What is the new temperature(°C) of the gas at a volume of 90.0 mL and a pressure of 3.20 atm? Set up Data Table P1 = 0.800 atm V1 = 180 mL T1 = 302 K P2 = 3.20 atm V2= 90 mL T2 = ??

  36. Learning Check A gas has a volume of 675 mL at 35°C and 0.850 atm pressure. What is the temperature in °C when the gas has a volume of 0.315 L and a pressure of 802 mm Hg?

  37. Practice • The gas in an aerosol can is at a pressure of 3.00 atm at 25°C. Directions on the can warn the user not to keep the can in a place where the temperature exceeds 52°C. What would the gas pressure in the can be at 52°C?

  38. You try! The volume of a gas is 27.5 mL at 22.0°C and 0.974 atm. What will the volume be at 15.0°C and 0.993 atm?

  39. One More Practice Problem A balloon has a volume of 785 mL on a fall day when the temperature is 21°C. In the winter, the gas cools to 0°C. What is the new volume of the balloon?

  40. And now, we pause for this commercial message from STP OK, so it’s really not THIS kind of STP… STP in chemistry stands for Standard Temperature and Pressure Standard Pressure = 1 atm (or an equivalent) Standard Temperature = 0 C (273 K) STP allows us to compare amounts of gases between different pressures and temperatures

  41. Try This One A sample of neon gas used in a neon sign has a volume of 15 L at STP. What is the volume (L) of the neon gas at 2.0 atm and –25°C?

  42. Constant temperature Constant pressure Avogadro’s Law Va number of moles (n) V = constant x n V1/n1 = V2/n2 5.3

  43. Dalton’s Law of Partial Pressures

  44. 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. Patm = Pgas + Pwater

  45. Dalton’s Law of Partial Pressure Problem Three of the primary components of air are carbon dioxide, nitrogen, and oxygen. In a sample containing only a mixture of these gases at exactly 1.00 atm., the partial pressure of the carbon dioxide and nitrogen are given as PCO2 = 0.285 torr, PN2= 593.525 torr. What is the partial pressure of oxygen?

  46. Dalton’s Law- You Try! • Three of the primary components of air are carbon dioxide, nitrogen, and oxygen. In a sample containing only a mixture of these gases. The partial pressure of the carbon dioxide, nitrogen, and oxygen are given as PCO2 = 0.350 atm, PN2= 75.2 kPa, and PO2 = 410. torr. What is the partial pressure of oxygen in atm? What is the total pressure?

  47. PA = nART nBRT V V PB = nA nB nA + nB nA + nB XB = XA = ni mole fraction (Xi) = nT Consider a case in which two gases, A and B, are in a container of volume V. nA is the number of moles of A nB is the number of moles of B PT = PA + PB PA = XAPT PB = XBPT Pi = XiPT 5.6

  48. 0.116 8.24 + 0.421 + 0.116 A sample of natural gas contains 8.24 moles of CH4, 0.421 moles of C2H6, and 0.116 moles of C3H8. If the total pressure of the gases is 1.37 atm, what is the partial pressure of propane (C3H8)? Pi = XiPT PT = 1.37 atm = 0.0132 Xpropane = Ppropane = 0.0132 x 1.37 atm = 0.0181 atm 5.6

  49. 2KClO3 (s) 2KCl (s) + 3O2 (g) PT = PO + PH O 2 2 Bottle full of oxygen gas and water vapor 5.6

  50. IDEAL GAS LAW P V = n R T Brings together gas properties. Can be derived from experiment and theory. BE SURE YOU KNOW THIS EQUATION!

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