1. Avogadro’s Principle Chapter 14 Section 14.2 Starts at Page 430 And Gas Stoichiometry 14.4 (p 440)

2. Avogadro’s Principle Equal volumes of gases at the same temperature and pressure contain equal numbers of particles.

3. Avogadro’s Principle Equal volumes of gases at the same temperature and pressure contain equal numbers of particles. Ideal Gas Equation PV = nRT V = nRT P

4. Avogadro’s Principle Equal volumes of gases at the same temperature and pressure contain equal numbers of particles. Ideal Gas Equation PV = nRT V = nRT P If V gas1 = V gas2 then n gas1 = n gas2

5. Remember one mole of anything contains 6.02 x 10 23 particles Molar volume for a gas is the volume that one mole occupies at 0.00°C and 1.00 atm pressure. –These conditions of temperature and pressure are known as standard temperature and pressure (STP)

6. One mole of any gas occupies a volume of 22.4 L at STP Very useful!!!! Example: 1 mole oxygen occupies 22.4 L at STP and contains 6.02 x 10 23 molecules of O 2 Avogadro showed experimentally that:

7. 1 mole oxygen occupies 22.4 L at STP and contains 6.02 x 10 23 molecules of O 2 1 mole Carbon dioxide occupies…….L at STP and contains………………………molecules CO 2 2 moles oxygen - ….. at STP and contains ……………….. molecules O 2 3 moles Carbon dioxide - …….L at STP and contains………………………molecules CO 2

8. 1 mole oxygen occupies 22.4 L at STP and contains 6.02 x 10 23 molecules of O 2 1 mole Carbon dioxide occupies 22.4 L at STP and contains 6.02 x 10 23 molecules CO 2 2 moles oxygen - 44.8L at STP and contains 1.20 x 10 24 molecules O 2 3 moles Carbon dioxide - 67.2 L at STP and contains 1.80 x 10 24 molecules CO 2

9. Test type questions: 1) Standard temperature and pressure (STP) are defined as Possible answers?

10. Test type questions: 1) Standard temperature and pressure (STP) are defined as Possible answers? 0°C and 1 atm pressure 273 K and 1 atm pressure 0°C and 760 mm Hg pressure 273 K and 760 mm Hg pressure 0°C and 101.325 kPa pressure

11. Test type questions: 2) Under which of the following sets of conditions will a 1 mole sample of {any gas} occupy a volume of 22.4 liters? Possible answers? This is the definition of molar volume – that 1 mole of any gas occupies 22.4 L at STP – appears on your reference sheet under Constants Volume of Ideal Gas at STP 22.4 L mol -1

12. Test type questions: 2) Under which of the following sets of conditions will a 1 mole sample of {any gas} occupy a volume of 22.4 liters? Possible answers? STP 0°C and 1 atm pressure (typically this) 273 K and 1 atm pressure 0°C and 760 mm Hg pressure 273 K and 760 mm Hg pressure 0°C and 101.325 kPa pressure

13. Test type questions: 3) Under which of the following sets of conditions will a 0.5 mole sample of {any gas} occupy a volume of 11.2 liters? Possible answers? Look carefully If 0.5 mole occupies 11.2 liters at this T and P What would 1 mole of this gas occupy?

14. Test type questions: 3) Under which of the following sets of conditions will a 0.5 mole sample of {any gas} occupy a volume of 11.2 liters? Possible answers? Look carefully If 0.5 mole occupies 11.2 liters at this T and P What would 1 mole of this gas occupy? twice as much = 22.4 liters = molar volume

15. Test type questions: 3) Under which of the following sets of conditions will a 0.5 mole sample of {any gas} occupy a volume of 11.2 liters? Possible answers? Any answer that shows Standard temperature and pressure (STP) 0°C and 1 atm pressure Or equivalent in other common units

16. Test type questions: 4) A sample of carbon dioxide gas occupies a volume of 20 L at standard temperature and pressure at (STP). What will be the volume of a sample of argon gas that has the same number of moles and pressure but twice the absolute temperature?

17. Using PV = nRT For the problem we have same number of moles of CO 2 and Argon = n, P doesn’t change PV = nRT or P = T nR V If T is doubled V must double to keep the ratio the same

18. OR Combined gas law – is for a fixed amount of gas – a fixed number of moles of gas P 1 V 1 = P 2 V 2 = constant T 1 T 2 P.V = (Constant).T

19. OR 4) A sample of carbon dioxide gas occupies a volume of 20 L at standard temperature and pressure at (STP). What will be the volume of a sample of argon gas that has the same number of moles and pressure but twice the absolute temperature? Use Avogadro’s principle – If equal volumes of gas contain equal numbers of particles under same conditions of T and P, then Equal numbers of moles of gas will occupy the same volume at the same T and P.

20. Test type questions: 4) A sample of carbon dioxide gas occupies a volume of 20 L at standard temperature and pressure at (STP). What will be the volume of a sample of argon gas that has the same number of moles and pressure but twice the absolute temperature? CO 2 V = 20 L at STP (0°C and 1 atm) Ar (same number of moles as the CO 2 ) so would also be same volume at STP V 1 = 20 L at STP

21. Test type questions: 4) …What will be the volume of a sample of argon gas that has the same number of moles and pressure but twice the absolute temperature? Ar V 1 = 20 L at STPV 2 = P 1 = 1atmP 2 = 1 atm T 1 = 273KT 2 = 2 x 273K = 546 K

22. Test type questions: 4) cont. Ar V 1 = 20 L at STPV 2 = P 1 = 1atmP 2 = 1 atm T 1 = 273KT 2 = 2 x 273K = 546 K 1atm. 20L = 1atm.V 2 273 K546 K V 2 = 1atm. 20L. 546 K= 40L 1atm. 273 K

23. Gas Stoichiometry CH 4(g) + 2 O 2(g)  CO 2(g) + 2 H 2 O (g) 1 mole2 moles 1 volume2 volumes 1volume2 volumes

24. CH 4(g) + 2 O 2(g)  CO 2(g) + 2 H 2 O (g) 1 volume2 volumes 1volume2 volumes Ex. Qu.: What volume of oxygen gas is needed for the complete combustion of 4.00 L of methane gas? (Assume constant temperature and pressure.) Look at relevant ratios in equation 1 : 2 or 1 volume of CH 4 will need 2 volumes O 2 1L:2L so4L:2L x 4 = 8L Answer: 4 L of methane will require 8.00 L of oxygen for complete combustion.

25. Ex. Qu. 2: What volume of oxygen gas is needed for the complete combustion of 4.00 L of ethane gas? (Assume constant temperature and pressure.) 2 C 2 H 6(g) + 5 O 2(g)  4 CO 2(g) + 6 H 2 O (g) 2 volumes :5 volumes Or 1 vol : 5/2 volumes 1L : 5/2 L 4L : 5/2 x 4

26. Ex. Qu. 2: What volume of oxygen gas is needed for the complete combustion of 4.00 L of ethane gas? (Assume constant temperature and pressure.) 2 C 2 H 6(g) + 5 O 2(g)  4 CO 2(g) + 6 H 2 O (g) 2 volumes : 5 volumes Or 1 vol : 5/2 volumes 1.00L : 5/2 L 4.00L : 5/2 x 4 L Answer: 4.00 L of ethane will require 10.00 L of oxygen for complete combustion.

27. Ex. Qu. 3: What volume of oxygen gas at STP is needed for the complete reaction of 107.92g of aluminum in the reaction below: 4 Al (s) + 3 O 2(g)  2 Al 2 O 3(s) 4 moles: 3 moles Look up atomic mass of aluminum 26.98 amu – remember 1 mole is atomic mass in g So here, 4 moles of Al would be 4 x (26.98g) = 107.92g Which is what we are provided with (yeah!)

28. Ex. Qu. 3: What volume of oxygen gas at STP is needed for the complete reaction of 107.92g of aluminum in the reaction below: 4 Al (s) + 3 O 2(g)  2 Al 2 O 3(s) 4 moles: 3 moles 107.92g Al needs 3 moles Oxgyen to react completely At STP 1 mole of any gas = 22.4 L 3 moles = 3 x 22.4 L = 67.2 L

29. Ex. Qu. 3: What volume of oxygen gas at STP is needed for the complete reaction of 107.92g of aluminum in the reaction below: 4 Al (s) + 3 O 2(g)  2 Al 2 O 3(s) 4 moles: 3 moles Answer: 67.2 L of oxygen at STP will be needed for complete reaction with 107.92 g of aluminum.

30. Homework Unit 5: Solids, Liquids, and Gases (Including Kinetic Molecular Theory and Avogadro’s Principle) Chemistry: Matter and Change Chapter 13 and 14 Review and test preparation – work booklet. Test – 20 multiple choice. Plus a graphing exercise. Friday March 8 th. Wednesday March 6 th – will be lab. Monday March 4 th, some time to address major issues with work booklet. Start next Unit.

31. Slip-Quiz Part 2 1.The temperature at which all molecular motion stops A 273 KB 273°C C 0KD freezing pt. 2. 1 mole of any gas occupies…at STP. A.6.03 x 10 23 L B 22.4 L C PV = nRTC 1 L