COMBINED AND IDEAL GAS LAWS

COMBINED GAS LAW

Do variables remain constant for gases???

Temperature, pressure, and volume are CONSTANTLY changing for a gas based on the conditionsGas amount (n) is constant

COMBINED GAS LAW (CONT.)

Combination of all three laws into one equation (Boyle’s, Charle’s, and Gay-Lussac’s Laws)

Describes the relationship between pressure, volume, and temperature

Focus on initial and final conditions

COMBINED GAS LAW

•P1V1 = P2V2

T1 T2

Temperature—Kelvin

EXAMPLE 1:

A gas has a volume of 80.0ml at 27°C and 0.200 atm. What volume will the gas have at standard conditions?

EXAMPLE 2:

• A gas has a volume of 60.0ml at standard conditions. This volume is reduced to 10.0ml 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 = nRT• P = pressure (atmospheres)• V = volume (liters)• T = temperature (Kelvin) • n = moles of the gas • R = 0.08206 Latm/molK (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 O2 (in grams) that could be stored at 21°C and 170atm in a cylinder with a volume of 60.0L.

EXAMPLE 2:

• Calculate the molecular weight of butane if 0.5813g of the gas fills a 250.0ml flask at a temperature of 24.4°C and a pressure of 742.6 mmHg.

EXAMPLE 3:

Calculate the density in grams per liter of O2 gas at 0°C and 1.00 atm.

EXAMPLE 4:

• A tank of hydrogen gas has a volume of 22.9L 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