Warm-Up 12/12/2016 The chemical equation below represents an unbalanced chemical reaction: Fe + O2  Fe2O3 When the equation is balanced, what coefficient is needed for Fe2O3? A)1 B) 2 C) 3 D) 4

Ideal Gases Ideal Gases are gases that behave the following ways: The particles do not interact with each other The gases behave as the Kinetic Molecular Theory predicts (KMT)

Ideal Gases Deviations Gases tend to behave less ideally at certain conditions 1. Low Temperature 2. High Pressure

Low Temperature’s Effect on Ideal Gases Gases behave less ideally at lower temperatures because the particles have less energy The lack of energy causes the particles to travel around the container slower thus allowing less interactions

Real Gases Most gases generally do not behave according to the ideal gas model These gases are called real gases Real gases behave slightly different

Ideal Gas Law The Ideal Gas Law combines pressure, temperature, volume, and amount of substance (moles) The Ideal Gas Law can be used to described a particular state of any gas

Ideal Gas Law Equation P * V = n * R * T

Ideal Gas Law Equation P = Pressure of the gas in atm V = Volume of the gas in Liters (L) n = number of moles of the gas T = temperature of the gas in Kelvin R = “Ideal Gas Law Constant”

Ideal Gas Law Equation R has several values depending on the pressure given: R = 0.0821 (L * atm) / (K * mol)

Example # 1 At what temperature would 2.10 moles of N2 gas have a pressure of 1.25 atm and in a 25.0 L tank?

Example Problem #2 You fill a rigid steel cylinder with a volume of 20.0 L with nitrogen gas to a final pressure of 20, 000 kPa at 27°C. How many moles of N2 gas does the cylinder contain?

Example # 3 What volume is occupied by 0.157 mols of O2 at 28°C and a pressure of 0.998atm?

Example Problem # 4 A sample of hydrogen gas has a volume of 8.56 L at a temperature of 0°C and a pressure of 1.5 atm. How many grams of H2 are present?

Example Problem # 5 A deep underground cavern contains 2.24 x 106 Liters of methane gas at a pressure of 1500 kPa and a temperature of 42°C. How many grams of methane(CH4) does this gas deposit contain?

How many grams are in a 273 cm3 sample of NH3 at 97.2 kPa and 61°C? Example # 6 How many grams are in a 273 cm3 sample of NH3 at 97.2 kPa and 61°C?

Example # 7 What is the pressure of the container, in atm, that has a volume of 200.0 L at 55.0 °C and 1.56 mol of NH3?

Example # 8 On hot days, you may have notice that potato chip bags seem to “inflate”, even though they have not been opened. If a I have a 250 mL bag at a temperature of 19 ˚ C, and I leave it in my car which has a temperature of 60 ˚ C, what will the new volume of the bag be?

Dalton’s Law of Partial Pressures - What happen if we mix gases of different pressures In order to understand what will happen, one must use Dalton’s Law of Partial Pressures: “The total pressure in a container is the sum of the partial pressures of ALL the gases in the container” Ptotal = P1 + P2 + P3 + . . . Pn

Dalton’s Law of Partial Pressures + = 10 atm + 5 atm = 15 atm 10 atm 5 atm

Example Problem 1. Four gases are mixed together. Each gas exerts a pressure of 550 torr, 450 torr, 750 torr, and 250 torr, respectively. What is the total pressure of the system?

Example # 2 A mixture of oxygen, hydrogen and nitrogen gases exerts a total pressure of 278 kPa.  If the partial pressures of the oxygen and the hydrogen are 112 kPa and 101 kPa respectively, what would be the partial pressure exerted by the nitrogen. Answer = 65 kPa

Dalton’s Law of Partial Pressure Continued So what if we said: ntotal = n1 + n2 + n3 + …. If each of the gases obeys the ideal gas equation, we can write : P1 = n1 (RT/V) , P2 =n2(RT/V), P3= n3 (RT/V) Ptotal = ( n1 + n2 + n3 + ….) (RT/V) = ntotal(RT/V)

Practice A gaseous mixture made from 6.00 g O2 and 9.00 g CH4 is placed in a 15.0 L vessel at 0˚ C. What is the partial pressure of each gas, and what is the total pressure in the vessel

Practice What is the total pressure exerted by a mixture of 2.00 grams of H2 and 8.00 grams of N2 at 273 K in a 10.0 L vessel?