CH1120

 Vary with respect to chemical properties but share some physical properties ◦ Low molar masses ◦ Non-metallic ◦ Expand spontaneously to fill container ◦ Volume of gas = volume of container ◦ Compressible ◦ Form homogeneous mixtures readily  All physical properties arise due to molecules being relatively far apart

 At room temperature: ◦ He ◦ Ne ◦ Ar ◦ Kr ◦ Xe ◦ H 2 ◦ N 2 ◦ O 2 ◦ F 2 ◦ Cl 2

 An increase in volume at a constant temperature causes pressure to decrease ◦ Syringe filled with air  A temperature increase at constant volume causes pressure to increase ◦ Balloon in winter

 SI unit = Pascal (Pa)  1Pa = 1N/m 2  1bar = 10 5 Pa  1atm = 760 torr = 760mmHg  1atm = 101.3Pa

 Remember how to calculate K  K = ℃  Used in gas law equations

 An inflated balloon has a volume of 6.0L at sea level (1.0atm) and is allowed to ascend until the pressure is 0.45atm. During ascent, the temperature of the gas falls from 22℃ to -21℃. Calculate the volume of the balloon at its final altitude.

 Each gas behaves independently of other gases in a mixture  At constant temperature and constant volume the total pressure of a gas sample is determined by the total number of moles of gas present

 Hypothetical gas whose pressure, volume, and temperature relationship are described completely by the ideal gas equation ◦ The molecules do not interact with one another ◦ The volume of the molecules is much smaller than the volume the gas occupies so we assume the molecules take up no space in the container  Very small error is introduced with these assumptions so it is acceptable ◦ When accurate calculations are needed we can correct for the assumptions

 Unit depend on units of P, V, n, and T  T in Kelvin  n is in mols  P usually atm  V usually L

UnitsNumerical Value

 Calcium carbonate, CaCO 3(s) decomposes upon heating to CaO (s) and CO 2(g). A sample of CaCO 3 is decomposed, and the carbon dioxide is collected in a 250mL flask. After decomposition is complete, the gas has a pressure of 1.3atm at a temperature of 31℃. How many moles of CO 2 gas were generated?  Use R to determine the units for all of the other components of your equation.

 When silver oxide is heated, it decomposes according to the reaction below. If 5.76g of Ag2O is heated and the O2 gas produced by the reaction is collected in a 0.65L flask at 25℃ what is the pressure of the O2 in the flask? 2Ag 2 O (s)  4Ag (s) + O 2(g)

 0℃ and 1atm are referred to as STP ◦ Standard temperature and pressure

 A sample of pure helium gas occupies a volume of 6.8 L at STP, how many grams of helium are present?