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Gas Laws Chemistry is Real gas. Pressure Pressure is force per unit area Standard atmospheric pressure 1 atmosphere 760 mm Hg = 760 torr 29.92 inches.

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Presentation on theme: "Gas Laws Chemistry is Real gas. Pressure Pressure is force per unit area Standard atmospheric pressure 1 atmosphere 760 mm Hg = 760 torr 29.92 inches."— Presentation transcript:

1 Gas Laws Chemistry is Real gas

2 Pressure Pressure is force per unit area Standard atmospheric pressure 1 atmosphere 760 mm Hg = 760 torr inches Hg kPa 14.7 psi

3 Barometers Mercury barometer

4 Manometers Open arm manometer

5 Manometers Open arm manometer

6 Manometers Closed arm manometer

7 Pressure Converting units Convert 728 torr into atmospheres. 728 torr x 1 atmosphere 760 torr = atm Convert 86 kPa into torr. 86 kPa x 760 torr kPa = 645 torr

8 Pressure and volume: Boyles Law As pressure is increased, volume decreases by the same fraction (constant temperature) P 1 V 1 = P 2 V 2 Find the new volume if the gas in a 4.5 mL syringe is compressed from 1.05 atm to 2.31 atm.

9 Boyles Law Make a list of variables P 1 = 1.05 atmV 1 = 4.5 mL P 2 = 2.31 atmV 2 = V 2 Plug variables into equation and solve for V atm x 4.5 mL = 2.31 atm x V atm 1.05 x 4.5 mL = V = 2.05 mL

10 Boyles Law Freddie Krueger compresses air in a syringe from 5.1 mL to 1.9 mL. If the gas was initially at 101 kPa, what is the new pressure? 101 kPa x 5.1 mL = P 2 x 1.9 mL 101 x 5.1kPa = P = 271 kPa

11 Boyles Law Kinetic explanation of Boyles Law – when volume is decreased, particles of a gas have less room and strike the walls of the container more often.

12 Temperature and volume: Charles Law As the temperature increases, the volume increases (constant pressure) V 1 /T 1 = V 2 /T 2 (T must be in kelvins) George of the Jungle has a syringe of nitrogen gas with volume 4.9 mL. The temperature of the jungle is 40ºC (313K). He places the syringe in a pot of boiling water (100ºC, 373K). What is the new volume?

13 Charles Law List variables: V 1 = 4.9mL T 1 = 313K V 2 = V 2 T 2 = 373K Plug variables into Charles Law equation and solve for V 2 4.9mL V 2 313K 373K =

14 Charles Law Solve for V 2 4.9mL V 2 313K 373K 4.9mLx373K = V 2 313K = 5.84 mL =

15 Charles Law Jim Jones has a syringe full of hydrogen cyanide gas (9.4 mL) at 33ºC. He submerges it in dry ice/carbon tetrachloride and the volume goes down to 7.6 mL. What is the temperature of the dry ice/carbon tetrachloride?

16 Charles Law V 1 /T 1 = V 2 /T mL 7.6 mL 306K T (306Kx7.6) T 2 (306Kx7.6)/9.4 = T 2 = 247K (-26ºC) = =

17 Charles Law Kinetic explanation of Charles Law – as temperature increases, the particles move faster and hit the walls of the container harder, increasing the volume. In a rigid container the pressure increases. (Gay-Lussacs Law)

18 Combined Gas law Combination of Boyles and Charles Laws P 1 V 1 = P 2 V 2 T 1 T 2 The amount of gas remains constant.

19 Combined Gas Law Jane compresses a sample of fluorine gas at standard pressure in a syringe from 6.2 mL to 2.3 mL. As she does this the temperature of the gas increases from 296K to 310K. What is the new pressure of the gas in atmospheres?

20 Combined Gas Law 1atm x 6.2 mL P 2 x 2.3 mL 296K 310K 1 x 6.2 x 310 P x 2.3 = 2.8 atm = =

21 Combined Gas Law JJ leaves his basketball on the hot pavement on a summer afternoon. The pressure in the ball increases from 20.7 psi to 21.3 psi. The internal temperature of the ball went from 22ºC to 41ºC. If the original volume was 5.2 liters, what is the final volume?

22 Combined Gas Law P 1 V 1 = P 2 V 2 T 1 T psi x 5.2 L = 21.3psi x V 2 295K 314K 20.7psi x 5.2 L x 314K = V 2 295K x 21.3psi = 5.4 L

23 Law of combining gas volumes Under the same conditions, equal volumes of any gas contain the same number of particles (Avogadros principle) Standard conditions – 0ºC (273K) and 1 atm Under standard conditions, one mole of a gas occupies 22.4 liters (molar volume)

24 Law of combining gas volumes In a reaction where all the reactants and products are gases, the mole ratios are also volume ratios 2H 2 + O 2 2H 2 O


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