2 DefinitionThe ideal gas law is the mathematical relationship among:Pressure (P)Volume (V)Temperature (T)Amount of the Gas in Moles (n)The law quantitatively describes the behavior of a gas sample for any combination of conditions:If you know three of the conditions, you can solve for the fourth.PV = nRT
3 Units of Measurement Volume must always be measured in liters (L). 1L = 1000mL = 0.001kLAmount of the gas must always be measured in moles (mol).If amount is given in grams, you must do a gram to mole conversion!Temperature must always be measured in Kelvin (K).K = ˚C ˚C = K - 273Pressure must always be measured in atmospheres (atm).1 atm = 760 mmHg = 760 torr = x 105 Pa = kPa
4 Standard Temperature and Pressure (STP) Standard temperature is 273 K.Standard pressure is 1 atm.At STP, 1 mole of any ideal gas occupies 22.4 L.
5 PV = nRT The Ideal Gas Constant Represented as R in the ideal gas law. R is a constant value that never changes.The value for R is derived from the standard volume (22.4L) of 1 mole of a gas at STP.PV = nRT can be arranged as R = PV/nTR = (1 atm)(22.4 L)/(1 mol)(273 K) = L•atm/mol•KPV = nRT
6 Solving Ideal Gas Law Problems What is the pressure exerted by a mol sample of nitrogen gas in a 10.0L container at 25˚C?1. Determine given values and unknown.n= mol, V = 10.0 L, T = 25˚C , R = L•atm/mol•KP = ?2. Convert given values into proper units.K = 25˚C = 298 K3. Rearrange equation to solve for unknown. Plug in given values to solve for unknown.P = nRT/VP = (o.500 mol)( L•atm/mol•K)(298 K) / 10.0 LP = 1.22 atm
7 Solving Ideal Gas Law Problems What is the volume of an 8.00g sample of oxygen gas at 293 K and atm?1. Determine given values and unknown.n= 8.00g, T = 293 K , P = atm, R = L•atm/mol•KV= ?2. Convert given values into proper units.8.oo g O2 x (1 mol O2 / g O2 ) = mol O23. Rearrange equation to solve for unknown. Plug in given values to solve for unknown.V = nRT/PV= (o.250 mol)( L•atm/mol•K)(293 K) / atmV = 6.17 L