1. Chapter 11 Gases

2. Pressure and Force ____________ (P): the force per _________ on a surface. ________ (N): the force that will increase the speed of a ___________ by _____________ each second the force is applied. ___________: a device used to measure ______________ pressure. 11-2

3. Units of Pressure Millimeters of Mercury: _________ = 1 torr Atmosphere: _______ = 760 mm Hg Pascal: the pressure exerted by a force of _________ acting on an area of _____________. 1 atm = 1.01325 x 10 5 Pa 1 atm = 101.325 KPa ______: standard temperature and pressure, 0 o C and 1 atm. Pounds per Square Inch (psi): 1 atm = ________ 11-3

4. Practice Ex. The barometer reads 758 mm Hg. What is the ________________________ in Pa? 758 mm Hg x 1.01325 x 10 5 Pa = 1.01 x 10 5 Pa 760 mm Hg 1) The air pressure in a tire is 109 kPa. What is the pressure in atm? 11-4

5. Dalton’s Law ________________: the pressure of each gas in a mixture of gases. _____________: the ___________ of a gas mixture is the ______________________ of the component gases. P T = P 1 + P 2 + P 3 … 11-5

6. Boyle’s Law _______________: the volume of a fixed mass of gas varies inversely with the pressure at constant temperature. _________________ Ex. A gas occupies a volume of ________ at a pressure of ________ and temp. _______. When the pressure is changed, the volume becomes _______. If there is no change in temp., what is the new pressure? (1.01 KPa) (458 ml) = P 2 (477 ml) P 2 = 0.970 kPa 11-6

7. Practice P 1 V 1 = P 2 V 2 2) A gas occupies a volume of 2.45L at a pressure of 1.03 atm and temp. 293 K. What volume will the gas occupy if the pressure changes to 0.980 atm and the temp. remains the same? 11-7

8. Charles’s Law _____________: the given value of zero in the Kelvin temperature scale. K = 273.15 + o C _____________: the volume of a fixed mass of gas at constant pressure varies directly with the ______________. __________ Ex. What will be the volume of a gas sample at ________ if it’s volume at __________? Assume that the pressure is constant. 3.42L = V 2 215K 309K V 2 = 4.92L 11-8

9. Practice 3) A gas sample at 83 o C occupies a volume of 1400m 3. At what temperature will it occupy 1200m 3 ? Assume that the pressure is constant. 11-9

10. Gay-Lussac’s Law ______________: the pressure of a fixed mass of gas at constant volume varies directly with the ______________. P 1 = P 2 T 1 T 2 Ex. The gas in a container is at a pressure of __________ at __________. Directions on the container warn the user not the keep it in a place where the temp exceeds ________. What would the pressure in the container be at 52 o C? 3.00 atm = P 2 298K 325K P 2 = 3.27 atm 11-10

11. Practice P 1 = P 2 T 1 T 2 4) At 120 o C the pressure of a sample of nitrogen is 1.07 atm, What will the pressure be at 205 o C, assuming constant volume? 11-11

12. Combined Gas Law P 1 V 1 = P 2 V 2 T 1 T 2 ____________________: expresses the relationship between pressure, volume and temp (K) of a fixed amount of gas. Ex. A helium balloon has a volume of ________________ and _________. What volume will it have at _______________? (1.08 atm)(50.0L) = (0.855 atm) V 2 298 K 283 K V 2 = 60. L 11-12

13. Gas Volumes ______________________________________: at a constant temp and pressure, the ___________ of gaseous reactants and products can be expressed as ratios of small whole numbers. (____________ in balanced eq. can represent ______________!) _________________: equal volumes of gases at the same temp. and pressure contain equal numbers of molecules. ___________ Volume = k(constant) x n(moles) _____________________: the volume occupied by one mole of a gas at STP is 22.4L. 11-13

14. Practice Ex. What volume does 0.0685 mol of gas occupy at STP? 0.0685 mol x 22.4 L = 1.53 L 1 mol Ex. What quantity of gas, in moles, is contained in 2.21 L at STP? 2.21L x 1 mol = 0.0987 mol 22.4 L 5)At STP, what is the volume of 7.08 mol of nitrogen gas? 11-14

15. Gas Stoich Given a volume, find a volume: Ex. When ________ of hydrogen reacts with bromine, what volume of HBr is produced? _________________ 0.75L H 2 x 2L HBr =1.5L HBr 1L H 2 11-15

16. Practice 6) What volumes of sulfur dioxide and dihydrogen sulfide gases are necessary to produce 11.4 L of water vapor? 11-16

17. Gas Stoich Ex. How many liters of CO 2 are produced at STP when 400.00g of CaCO 3 react with HCl? CaCO 3 + HCl → CaCl 2 + CO 2 + H 2 O ________________________________ 400.00g CaCO 3 x 1mol CaCO 3 x 1mol CO 2 x 22.4L 100.04g CaCO 3 1mol CaCO 3 1mol CO 2 = ______________ 11-17

18. Gas Stoich Ex. Find the mass of sugar required to produce __________ at STP in the rxn: C 6 H 12 O 6 → 2C 2 H 6 O + 2 CO 2 1.82L CO 2 x 1mol CO 2 x 1molC 2 H 12 O 6 x 180.18gC 6 H 12 O 6 22.4L 2mol CO 2 1 mol = ____________________ 11-18

19. Ideal Gas Law _____________: the mathematical relationship among pressure, volume, temperature and the number of moles of a gas. Ideal Gas Law: ______________ How R (the ideal gas law constant) is derived: R = (1 atm)(22.4L) = _________________ (1 mol)(273K) 11-19

20. Ideal Gas Law Ex. If the pressure exerted by a gas at ____ in a volume of ______________, how many moles of gas are present? (5.00atm)(0.0010L) = n(0.0821atmL/molK)(273K) n = __________________ 11-20

21. Practice 7) What volume would be occupied by 100. g of oxygen gas at a pressure of 1.50 atm and a temp. of 25 o C? 11-21

22. Diffusion and Effusion ____________________: rates of effusion of gases at the same temperature and pressure are __________________ to the _______________ of their molar masses. rate of effusion of A = √M B rate of effusion of B √M A 11-22

23. Diffusion and Effusion rate of effusion of A = √M B rate of effusion of B √M A Ex. Compare the rate of effusion of hydrogen and oxygen at the same temp. and pressure. rate of effusion of H 2 = √32.00 g/mol = 3.98 rate of effusion of O 2 √2.02 g/mol 11-23

24. Practice rate of effusion of A = √M B rate of effusion of B √M A 8) A sample of hydrogen effuses through a porous container about 9 times faster than an unknown gas. Estimate the molar mass of the unknown gas. 11-24

25. Ch. 11 The End! 11-25