AP Chemistry D. Paskowski GAS LAWS Review AP Chemistry D. Paskowski

Gases Least dense of the three basic forms of matter Takes the shape of its container by expanding to fill the container Flows Continually moving

Physical Conditions (briefly) Volume – given enough volume a gas will expand indefinitely Pressure – gases exert pressure when confined Temperature – increases the movement of gases Moles – influence pressure and volume

Laws – Observed Behavior of Gases Boyle’s Law: Pressure and Volume are inversely proportional Pressure increases when volume decreases, PV initial = PV final Gay Lussac: Pressure and Temperature are directly proportional Pressure increases when Temperature increases, P/T initial = P/T final

Laws – Observed Behavior of Gases (continued) Charles’ Law: Volume and Temperature are directly proportional Volume increases when Temperature increases, V/T initial = V/T final Avogadro’s Law: Volume is directly proportional to the number of moles Equal volumes of gases at the same temperature and pressure contain the same number of particles of gas, V/n initial = V/n final @ STP  1 mole of any gas = 22.4 L

Combined Gas Law SO V = a/P P = Tb V = Tc PV = k*T when the number of moles of gas is constant So when conditions change, we can solve for the unknown using the following PV/T initial = PV/T final because they both equal k* Lets do the example problems for the gas laws

Boyle’s law You have a 1.53 L sample of SO2 gas at a pressure of 5.6 x 103 Pa. If the pressure is changed to 1.5 x 104 Pa at constant temperature, what is the new volume?

Charles’s Law A sample of gas at 15oC and 1 atm has a volume of 2.58 L. What volume will this gas occupy at 38oC and 1 atm?

Avogadro’s Law We have a 12.2 L sample containing 0.50 mol of oxygen gas at a pressure of 1 atm and temperature of 25oC. If all this O2 were converted to ozone, O3, at the same temperature and pressure, what would be the volume of ozone?

Ideal Gas Law So combining all of the above laws gives us the ideal gas law PV = nRT Where P is in atmospheres, V is in liters, n is moles, T in Kelvin temperature, and R is the universal gas constant Gas Stoichiometry often requires the use of the ideal gas law.

Ideal Gas Law Problems A sample of hydrogen gas has a volume of 8.56 L at a temperature of 0oC and a pressure of 1.5 atm. Calculate the moles of hydrogen present in this sample.