• Alteration of combined gas law– IGL calculates the number of moles of a gas

in a fixed volume at a known temperature and pressure

• Relates Moles, Pressure, Volume, & Temperature

• Describes the behavior of an “ideal” gas

• Cannot be used when a gas

is at its critical points

(Extreme Temperatures & Pressures or Phase Changes)

Real Gasses?

• Gases in the real world

• A gas that cannot be explained or described by the Ideal Gas Law

• Take into account:– Compressibility– Specific heat capacity– Van der Waals forces

• Defined in an environment in which all collisions between molecules or atoms are perfectly elastic (no intermolecular forces)

• An ideal gas has no forces of attraction between molecules (IM forces)

• The molecules in the gas occupy “no volume”

• There is no such thing as an “Ideal Gas”

But what does PV=nRT mean?Four Variables

• P = pressure (must be converted to kPa or atm)

• V = volume (must be converted to Liters)• T = temperature (must always be in K)• n = moles

Universal Gas ConstantR = 0.0821 L atm/ K mole or

-Used to interrelate the variables of a gas

• Derived from Boyle’s, Charle’s and Avagadro’s law from the Ideal Gas Law

• Constant n & T = Boyle’s Law

• Constant n & P = Charles’s Law

• Constant P & T = Avogadro’s Law

• Constant n & V = Gay Lusac’s Law

• We can calculate the value of R from the other variables in the ideal gas equation.

• At STP (O degrees C or 273.15 K) and a pressure of 1 atm at the standard molar volume (22.414 L) We can solve for R

• R= 0.0821 L atm/ K mole

• Can be used to describe the behavior of real gases at pressures around or less than 1 atm and temperatures around room temperature

• Gases like this behave close enough to an ideal gas such that PV=nRT can adequately describe their behavior

A 1.50 mole sample of Helium is placed in a 15.0 L container at 400K. What is the pressure in the container?

Answer: 332 kPa

• Evan has 23.7 grams of nitrogen gas in a 30.8 L container with a pressure of 1.5 atm. What is the temperature of the gas?

• Answer: 670 K

• Pratheek has 2.03 moles of Helium in a 400.1 mL container at 282 degrees Celsius. What is the pressure of this gas in kPa?

• Answer: 23400 kPa