1. The Molar Volume Chapter 10 – Blue Book HW: #1-17, 19-20 & 23-24 #1-11 DUE NEXT CLASS!!!

2. I.Avogadro’s Principle & Molar Volume A.Relationship between the mass of a gas & its volume: 1.Equal volumes of all gases, measured under the same conditions of P & T, contain the same number of particles. a.1 mole of any gas @ STP contains 6.02 x 10 23 particles b.1 mole of any gas has a mass = to its molecular mass *EXAMPLES:* ** 1 mole N 2 = 28.0 g N 2 = 6.02 x 10 23 molecules of N 2 molecules of N 2 ** 1 mole of CO 2 = 44.0 g CO 2 = 6.02 x 10 23 molecules of CO 2 ** 1 mole of CO 2 = 44.0 g CO 2 = 6.02 x 10 23 molecules of CO 2 c.1 mole of any gas (@STP) = molecular mass = 22.4 dm 3 of the gas

3. Examples 1.A sample of gas has a mass of 1.248 g and occupies 300.0 cm 3 at STP. What is the molecular mass of this gas? Solving Process: The molecular mass of the gas is equal to one mole of the gas. Start with the relationship between volume & mass & calculate the mass of one mole of the gas. All units must be divided out except g/mol.

4. Examples 1.How many grams of CO 2 will occupy a volume of 500 cm 3 at STP? Remember: 1 mol CO 2 = 22.4 dm 3 CO 2 at STP 1 mol CO 2 = 44.0 g CO 2

5. II. Molar Volume & Gases Collected Over Water A.We can apply what we know about molar volume to lab situations involving gases collected over water Example: A reaction produces 200 cm 3 of oxygen over water and measured at 22 o C and 99.2 kPa. How many grams of the gas are produced? Assume water vapor pressure of 2.6 kPa at 22 o C.

6. III. Ideal Gas Equation A.Combo of the four physical variables: pressure, volume, temperature & number of particles. 1.Equation: PV = n RT P = pressure in kPa V = volume dm 3 T = temperature in K n = number of moles of a gas R = 8.31 (dm 3 x kPa) / (mol x K) * (other values for R depending on the units) 2.n = m/Mm = massM = molecular mass Other ways to manipulate the Ideal Gas equation: 3.PV = (m/M)RT 4.M = (mRT)/PV

7. Example 3.A flask has a volume of 258 cm3. A gas with a mass of 1.475 g is introduced into the flask at a temperature of 300K and a pressure of 98.6 kPa. Calculate the molecular mass of the gas using the ideal gas equation.

8. IV Gas Concentration A.Can be expressed many ways: 1.Percent by volume – volume of the given compound contained in 100 volumes of air (example air contains about 20% O 2 by volume) 2.Parts per million (ppm) - # of mg of a compound per one kg of the whole. 3.Parts per billion (ppb) - # of μg (micrograms) per kg of the whole. Examples: 1 ppm is $.01 in $10,000 1ppb is $.01 in $10,000,000 1ppb is $.01 in $10,000,000 1 ppm is 1mm in 1km 1 ppm is 1mm in 1km 1 ppb is 1mm in 1000 km 1 ppb is 1mm in 1000 km