# gases

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Presented by Karen Compton, Jane Smith and Claudia Wallace in the ACT2 stand at CAST2010 in Houston, Texas

TRANSCRIPT

• 1. Gases

2. Gases

• (7) Science concepts . The student knows the variables that influence the behavior of gases. The student is expected to:
• (A)describe interrelationships among temperature, particle number, pressure, and volume of contained within a closed system; and
• (B)illustrate the data obtained from investigations with gases in a closed system and determine if the data are consistent with the Universal Gas Law.
• (4) (C) compare solids, liquids, and gases in terms of compressibility, structure, shape, and volumeSupporting
• (9) Science concepts.The student understands the principles of ideal gas behavior, kinetic molecular theory, and the conditions that influence the behavior of gases.
• The student is expected to:
• (A) describe andcalculatethe relations between volume, pressure, number of moles, and temperature for an ideal gas as described by Boyle's law, Charles' law, Avogadro's law, Dalton's law of partial pressure, and the ideal gas lawReadiness

3. Gases

• (7) Science concepts . The student knows the variables that influence the behavior of gases. The student is expected to:
• (A)describe interrelationships among temperature, particle number, pressure, and volume of contained within a closed system; and
• (B)illustrate the data obtained from investigations with gases in a closed system and determine if the data are consistent with the Universal Gas Law.
• (B)perform stoichiometriccalculations , including determination of mass and volume relationships between reactants and products for reactions involving gasesSupporting
• (C) describe the postulates of kinetic molecular theory.Supporting

4. Gases-CCRS

• Properties and behavior of gases, liquids, and solids
• Understand the behavior of matter in its various states: solid, liquid, and gas.
• a. Describe how gas pressure is affected by volume, temperature, and the addition of gas.
• b. Describe the behavior of solids, liquids, and gases under changes in pressure.

5. Gases-CCRS

• 3. Understand principles of ideal gas behavior and kinetic molecular theory.
• a. Use the kinetic molecular theory to explain how gas pressure is affected by volume, temperature, and the addition of gas.
• b. Distinguish between real and ideal gas behavior, and identify the criteria in the kinetic molecular theory that conflict with the properties of real gases.
• 4. Apply the concept of partial pressures in a mixture of gases.
• a.Use Daltons Law to determine the partial pressure of a gas in a mixture of gases.

6. Prior Knowledge

• Dimensional analysis
• Characteristics of the 3 phases of matter
• Direct and inverse relationships

7. Engage

• Simulate a gas with particles in a box

8. KMT thinking about gas particles

• If you pour a sample from a small box into a large box, what changes?What stays constant?
• If you pour a sample from a large box into a small box, what changes?What stays constant?
• What if the boxes are connected and a valve is opened?
• If you heat up the sample, what happens?
• What does adding particles do?

9. Gas Law Problems

• Rather than learning all of the laws separately, use:

Prediction: ______________________ What conversions are necessary? Variable Initial Final P V n T 10. Gas Formulas = = Pressure)(Volume) = (moles)(Ideal Gas Constant)(Temperature)PV = nRT Total pressure of a gas = sum of the partial pressures of the component gas P t= P 1+ P 2+ P 3+ 11. A sample of gas occupies a volume of 1.60 L at a pressure of 720. torr.What would be the pressure of this gas if it were compressed to 1.20 L at the same temperature?

• 540. torr
• 960. torr
• 360. torr
• 1440 torr

12. Two flasks are connected by a stopcock as shown below.The 5.0 L flask contains CH 4at a pressure of 3.0 atm, and the 1.0 L flask contains C 2 H 6at a pressure of 0.55 atm.Calculate the pressure of CH 4after the stopcock is opened.Assume that the temperature remains constant. 13. Gas Law Problems What conversions are necessary? Variable Quantity Conversions P V n T 14. What would be the mass of400. mL of hydrogen collected at 20 C and 740 torr? 15. P t= P 1+ P 2+ P 3+ A gaseous mixture containing 1.5 moles argon and 3.5 moles of carbon dioxide has a total pressure of 7.0 atm.What is the partial pressure of carbon dioxide? 16. P atm =P gas+P water vapor 17. Gas Stoichiometry

• At STP,22.4 L=1 mole
• At other conditions, use PV = nRT to solve for moles

18. 2 K + 2 H 2 O2 KOH + H 2

• Calculate the volume of hydrogen gas produced at standard temperature and pressure when 18.0 grams of potassium is reacted with an excess of water.
• If400. mL of hydrogen was prepared by reacting magnesium with hydrochloric acid 20 o C and 740 torr, what mass of magnesium was required?

19. Each of the following examples gives a change in volume, temperature, amount, or pressure of a gas sample.Indicate whether the other variable mentioned would increase or decrease.If a variable is not mentioned, assume it is constant.