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Overall Objective: Understand and apply the properties of gases and the gas laws. Iowa Model Core standards addressed: o Understands and applies knowledge of the structure and properties of matter o Designs and conducts scientific investigations o Uses technology and mathematics to improve investigations and communications o Apply critical literacy/thinking skills related to personal, family and community wellness. o Apply digital tools to gather, evaluate, and use information. Key Concepts: 1. Explain why gases are easier to compress than solids or liquids are. (14.1.1) 2. Describe the three factors that affect gas pressure. (14.1.2) 3. Describe the relationships among the temperature, pressure, and volume of a gas. (14.2.1) 4. Use the combined gas law to solve problems. (14.2.2) 5. Compute the value of an unknown using the ideal gas law. (14.3.1) 6. Compare and contrast real and ideal gases. (14.3.2) 7. Understand the effects of CO 2 on the atmosphere and its impact on climate change. Page 2 of 11
Atmospheric Pressure Practice The values for standard atmospheric pressure in different units are as follows: Units of Gas Presure Units Standard Pressure Atmosphere 1 atm (exactly) Inches of mercury 29.9 in. Hg cm of mercury 76 cm Hg (exactly) mm of mercury 760 mm Hg (exactly) torr 760 torr (exactly pounds per square inch 14.7 psi kilopascal 101 kpa If oxygen gas in a steel cylinder is at a pressure of 5.25 atm, what is the pressure in each of the following units? A) mm Hg B) torr C) cm Hg D) inches Hg If an automobile piston compresses a fuel-air mixture to a pressure of 7555 torr, what is the pressure expressed in each of the following units? A) psi B) kpa An American newscast states that the barometer reads 28.8 inches of Hg. Express the atmospheric pressure in each of the following units: A) atm B) mm Hg C) cm Hg D) torr Page 3 of 11
Ideal Gas Behavior State the five characteristics of an ideal gas according to the kinetic theory. At what Celsius temperature does a gas possess zero kinetic energy? Temperature Conversions Convert the following temperatures to the unit asked for: 1) 273K to o C 2) 0 o C to o F 3) 0K to o C 4) 23 o C to o F 5) The boiling points of five liquids are provided in either Celsius or Kelvin temperatures. List the liquids in order from the one with the lowest boiling point to the one with the highest boiling point. Acetone (C 3 H 6 O) 329K Heptane (C 7 H 16 ) 98 o C Nitromethane (CH 3 NO 2 ) 374K Benzene (C 6 H 6 ) 80 o C Sulfur Trioxide (SO 3 ) 318K Page 4 of 11
Boyle s Law Practice P 1 V 1 = P 2 V 2 Sketch a graph of pressure versus volume, assuming temperature is constant. Label the vertical axis V, and the horizontal axis P. A sample of air at 0.750atm is expanded from 250.0mL to 655.0mL. If the temperature remains constant, what is the final pressure in atm? What is the final volume of argon gas if 2.50L at 750 torr is compressed to a pressure of 150 torr? Assume the temperature remains constant. A 1.50 L sample of methane gas exerts a pressure of 1650 mm Hg. Calculate the final pressure if the volume changes to 7.00 L. Assume temperature remains constant. A 50 ml sample of carbon monoxide gas at 25 o C has a pressure of 15.0 psi. If the final volume is 44.0 ml at 25 o C, what is the final pressure in psi. Page 5 of 11
Charles Law Practice V 1 /T 1 = V 2 /T 2 Sketch a graph of volume versus Kelvin temperature, assuming pressure is constant. Label the vertical axis V, and the horizontal axis T(K). A 335-mL sample of oxygen at 25oC is heated to 50oC. If the pressure remains constant, what is the final volume in milliliters? What is the final Celsius temperature if 4.50 L of nitric oxide gas at 35oC is cooled until the volume reaches 1.00 L? Assume the pressure remains constant. A 275 L helium balloon is heated from 20 o C to 40 o C. Calculate the final volume assuming the pressure remains constant. A krypton balloon has a volume of 555 ml at 21 o C. If the balloon is cooled and the volume decreases to 475 ml, what is the final temperature? Assume the pressure remains constant. Page 6 of 11
Gay-Lussac s Law Practice P 1 /T 1 = P 2 /T 2 Sketch a graph of pressure versus Kelvin temperature, assuming volume is constant. Label the vertical axis P, and the horizontal axis T(K). A sample of ammonia gas at 760 torr is heated from 20 o to 200 o C. If the volume remains constant, what is the final pressure in torr? A sample of xenon gas at 20 o C and 0.570 atm is cooled to a pressure of 0.100 atm. If the volume remains constant, what is the final Celsius temperature. A 1.00-L sample of neon gas at 0 o C has a pressure of 76.0 cm Hg. If the gas is heated to 100 o C, what is the final pressure in cm Hg if the volume remains constant? Page 7 of 11
Combined Gas Law P 1 V 1 = P 2 V 2 T 1 T 2 A 100.0-mL sample of hydrogen gas is collected at 772 mm Hg and 21 o C. Calculate the volume of hydrogen at STP. A 5.00-L sample of nitrogen dioxide gas is collected at 5.00 atm and 500 o C. What is the volume of nitrogen dioxide under standard conditions? If a sample of air occupies 2.00 L at STP, what is the volume at 75 o C and 365 torr? A sample of hydrogen fluoride gas has a volume of 1250 ml at STP. What is the pressure in torr if the volume is 255 ml at 300 o C? A sample of air occupies 0.750 L at standard conditions. What is the pressure in atm if the volume is 100.0 ml at 25 o C? A sample of krypton gas has a volume of 500.0 ml at 225 mm Hg and -125 o C. Calculate the pressure in mm Hg if the gas occupies 220.0 ml at 100 o C. Page 8 of 11
Ideal Gas Law Practice PV=nRT R=0.0821 atm*l/mol*k If 5.00 mol of hydrogen gas occupies 50.0 ml at 25 o C, what is the pressure in atmospheres? If 1.25 mol of oxygen gas exerts a pressure of 1200 mm Hg at 25 o C, what is the volume in liters? If 10.0 L of nitrous oxide exerts a pressure of 125 psi at 373 K, what is the number of moles? If 0.100 mol of argon gas occupies 2.15 L at 725 torr, what is the temperature in degrees Celsius? A sample of unknown gas weighs 1.95 g and occupies 3.00 L at 1.25 atm and 20 o C. What is the molar mass of the unknown gas? A sample of chlorine gas occupies 1550 ml at 0.945 atm and 50 o C. What is the mass of the sample? Page 9 of 11
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