1. Ideal Gas Law

2. Ideal Gases Ideal Gases –are at high temperatures and low pressures. –have no forces of attraction between particles. –Collide elastically (no loss in kinetic energy). Real Gases Real Gases It is rare that we see a gas behaving in an ideal manner. It is rare that we see a gas behaving in an ideal manner. Most gases actually show very small attractive and repulsive forces between particles and collide inelastically (kinetic energy is lost). Most gases actually show very small attractive and repulsive forces between particles and collide inelastically (kinetic energy is lost).

3. Ideal Gas Law : PV = nRT Where P = pressure V = volume in Liters n = number of mols R = ideal gas constant T = temperature (Kelvin)

4. Calculate R, the Ideal Gas Constant… Using 1 mol of gas at STP and molar volume Using 1 mol of gas at STP and molar volume R = 0.0821 atm·L R = 0.0821 atm·L mol·K mol·K = 62.4 mmHg·L = 62.4 mmHg·L mol·K mol·K = 8.314 kPa·L = 8.314 kPa·L mol·K mol·K

5. Example… Calculate the number of moles of gas contained in a 3.0L vessel at 33°C and a pressure of 1.50 atm. Calculate the number of moles of gas contained in a 3.0L vessel at 33°C and a pressure of 1.50 atm.PV=nRT (1.50 atm) (3.0 L) = n (0.0821atm·L/mol·K)(306K) n = 0.18 moles

6. Variations… We don’t always know the number of moles, but we have the mass. We don’t always know the number of moles, but we have the mass. –n = m/M so… PVM = mRT –d= m/V so… PM = dRT

7. Example… Calculate the grams of oxygen gas present in a 2.50L sample kept at 1.66 atm pressure and a temperature of 10.0 °C. Calculate the grams of oxygen gas present in a 2.50L sample kept at 1.66 atm pressure and a temperature of 10.0 °C. PVM = mRT (1.66 atm)(2.50 L)(32 g/mol) = m (0.0821atm·L/mol·K)(283 K) m = 5.72 g

8. Examples… What is the density of NH 3 at What is the density of NH 3 at 800 mmHg and 25 °C? PM = dRT (800 mmHg)(17 g/mol) = d (62.4 mmHg·L/mol·K)(298 K) d = 0.7 g/L