COMBINED AND IDEAL GAS LAWS COMBINED GAS LAW
COMBINED AND IDEAL GAS LAWS
COMBINED GAS LAW v. Do variables remain constant for gases? ? ? v. Temperature, pressure, and volume are CONSTANTLY changing for a gas based on the conditions v. Gas amount (n) is constant
COMBINED GAS LAW (CONT. ) v. Combination of all three laws into one equation (Boyle’s, Charle’s, and Gay-Lussac’s Laws) v. Describes the relationship between pressure, volume, and temperature v. Focus on initial and final conditions
COMBINED GAS LAW • P 1 V 1 = P 2 V 2 T 1 T 2 v. Temperature—Kelvin
EXAMPLE 1: A gas has a volume of 80. 0 ml at 27°C and 0. 200 atm. What volume will the gas have at standard conditions?
EXAMPLE 2: • A gas has a volume of 60. 0 ml at standard conditions. This volume is reduced to 10. 0 ml at 25. 0°C. What is the necessary pressure for this volume reduction?
IDEAL GAS LAW • Describes the general relationship among the variables: • • Temperature Pressure Volume Number of moles of gas • Enables us to determine the value of a variable if the other three variables are known
IDEAL GAS LAW (CONT. ) • PV = n. RT • • • P = pressure (atmospheres) V = volume (liters) T = temperature (Kelvin) n = moles of the gas R = 0. 08206 L atm/mol K (ideal gas constant)
EXAMPLE 1: Many gases are available for use in the laboratory among compressed gas cylinders stored at high pressures. Calculate the mass of O 2 (in grams) that could be stored at 21°C and 170 atm in a cylinder with a volume of 60. 0 L.
EXAMPLE 2: • Calculate the molecular weight of butane if 0. 5813 g of the gas fills a 250. 0 ml flask at a temperature of 24. 4°C and a pressure of 742. 6 mm. Hg.
EXAMPLE 3: Calculate the density in grams per liter of O 2 gas at 0°C and 1. 00 atm.
EXAMPLE 4: • A tank of hydrogen gas has a volume of 22. 9 L and holds 14. 0 mol of gas at 12°C. What is the reading on the pressure gauge in atmospheres?
HOMEWORK • Finish Gas Study Chart
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