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The Ideal Gas Law. Real Gas Behaviour. There are several assumptions in the kinetic molecular theory that describe an ideal gas Gas molecules have zero volume Forces of attraction/repulsion are zero Molecules move in straight lines Collisions are completely elastic
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Real Gas Behaviour • There are several assumptions in the kinetic molecular theory that describe an ideal gas • Gas molecules have zero volume • Forces of attraction/repulsion are zero • Molecules move in straight lines • Collisions are completely elastic • However, at high pressure and low temperature there are problems with these assumptions • In very small volumes there will be many more interactions and collisions • The volumes of the gas molecules is now a significant fraction of the container
The Ideal Gas Law Boyle’s Law: PV = k or V = k P Charles’ Law: V = k or V = aT T Avogadro’s Law: V = b or V = bn n V = kab X nT P V = RnT or PV = nRT P
PV= nRT Unit Analysis! PV = nRT R = PV nT R = (kPa)(L) (mol)(T) R = 8.314 kPa·L/mol·K P = pressure (kPa) V = volume (L) n = amount (mol) T = temperature (K) R = ??
Try These… • Use the ideal gas law to calculate the molar volume of a gas at SATP. • A cylinder of laughing gas (N2O) has a diameter of 23.0 cm and a height of 140 cm. The pressure is 108 kPa at a temperature of 294 K. How many grams of laughing gas are in the cylinder? Hint: Vcylylinder = r2h
Homework • Read p. 443-445 • P. 445 #3,4,6 • P. 448 #1-6