1. Chapter 11
Gases Part II

2. Avogadro’s Law
Avogadro’s Law – Equal volumes of gases at the same temp and press have the same number of molecules. Illustrate.

3. Standard Molar Volume of a Gas –
Volume of mole of gas at STP = L
1 mole gas = 22.4 L (STP)

4. Examples
1. A chemical reaction produced moles of oxygen gas. What is the volume at STP?

5. 2. What is the mass of 98 mL of sulfur dioxide at STP?

6. Ideal Gas Law
Ideal Gas Law – relationship between P, V, n, T for one gas alone.

7. PV = nRT
P = press in atm
V = volume in L
n = moles
R = universal gas constant
= Latm
molK
T = Kelvin

8. Memorize the value and units of R
See different values of R on pg. 342

9. 1. What is the volume, in liters, of 0
1. What is the volume, in liters, of moles of oxygen gas at 20C and atm?

10. 2. What is the volume of 25.36 g of nitrogen gas, N2, at 0C and 765 mm Hg?

11. 3.
a. What is the molar mass of a 1.00 liter gas at 28C and atm. The gas has a mass of 5.16 g?

12. b. What is the density of the gas?

13. Gas Stoichiometry Review the 4 steps of stoichiometry problems: Step 1

14. Volume – Volume Calculations
1. What will be the volume of oxygen at STP needed for the complete combustion of L of propane, C3H8?

15. Volume – Mass Calculations
2. How many grams of calcium carbonate must be decomposed to produce 5.00 L of carbon dioxide at STP? CaCO3  CaO + CO2

16. Gas Stoichiometry with New Conditions
Tungsten is produced for light bulbs by this reaction:
WO H2  W + 3H2O
How many liters of hydrogen at 35C and atm are needed to react completely with 875 g of tungsten oxide?

17. 2. What volume of chlorine gas at 38C and 1
2. What volume of chlorine gas at 38C and 1.63 atm is needed to react completely with 10.4 g of sodium to form NaCl?

18. Graham’s Law of Effusion
The rates of effusion of gases at the same temp and press are inversely proportional to the square roots of their molar masses.
Rate of effusion of A = MB = densityB
Rate of effusion of B = MA densityA

19. Examples
1. Compare the rates of effusion of hydrogen and oxygen at the same temp and press.