1. UNIT 6: CHEMICAL QUANTITIES Chapter 10: Mole and Volume Relationships

2. The Mole and Volume Relationships  We know that the mass for one mole for different substances will vary because of the molar mass  How about volume?

3. The Mole and Volume Relationships  The volume for a substance will vary because each substance has a different number of atoms in them and each atom is a different size  This is true for liquids and solids  A gas occupies the same amount of space regardless of the size of the atom or molecule

4. The Mole and Volume Relationships  Avogadro's Hypothesis  Equal volumes of gases at the same temperature and pressure contain equal numbers of particles.  STP  Standard Temperature and Pressure  Temperature is equal to 0˚ C  Pressure is equal to 101.3 kPa or 1 atm  At STP, 1 mol or 6.02 x 10 23 representative particles, of any gas occupies a volume of 22.4 L.  1 mole = 6.02 X 10 23 = 22.4 L

5. The Mole and Volume Relationship  Calculating Volume at STP Volume of gas = Moles of gas X  Practice  Determine the volume in liters of 0.60 mol SO 2 gas at STP 22. 4 L 1 mol 0.60 mol SO 2 22. 4 L SO 2 = 13 L SO 3 1 mol SO 2

6. Volume and Molar Mass Relationship  Using Density to find the molar mass of a gas  Cannot find the mass of a gas by weighing it  Remember Density = Mass / Volume or Grams / Liters  Molar mass = density at STP × Molar volume at STP = × Grams mole Grams Liter 22.4 Liters 1 Mole

7.  Example  The density of a gaseous compound containing carbon and oxygen is found to be 1.964 g/L at STP. What is the molar mass of the compound? 1.964 g22. 4 L = 44.0 g/mol 1 L 1 mol Volume and Molar Mass Relationship

8. Mixed Mole Problems Use the map to be able to convert g  atoms, molecules  liters, liters  grams, or any other combination. ALWAYS convert to moles first!

9.  Example  What is the volume, in liters, of 835 g SO 3 at STP?  Find out where on the map you are starting (given value)  Convert to moles  Then use the conversion to get where you need to end on the map.  Molar Mass SO 3 = 80.1 g/mol Volume and Molar Mass Relationship 835 g 1 mol 22.4 L = 234 L SO 3 80.1 g 1 mol

10.  Example  What is the mass, in grams, of a molecule of aspirin (C 9 H 8 O 4 )?  Molar Mass C 9 H 8 O 4 = 180.0 g/mol Volume and Molar Mass Relationship 1 molec 1 mol 180.0 g = 2.99×10 -22 g aspirin 6.02×10 23 molec 1 mol