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Gases. Standard Temperature and Pressure. In order to compare two gases, we choose a standard temperature and pressure:
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Standard Temperature and Pressure • In order to compare two gases, we choose a standard temperature and pressure: STP: standard temperature and pressure → 273.15 K and 101 kPa → one mole of gas has a volume of 22.4 L SATP: standard ambient temperature and pressure → 298.15 K and 100 kPa → one mole of gas has a volume of 24.8 L
F (N) P = A (m2) Pressure • gases exert a pressure on the walls of their container. • pressure is defined as force per unit area: SI unit: 1 N/m2 = 1 Pascal (Pa)
Atmospheric Pressure The atmospheric pressure can be measured using a barometer.
Standard atmospheric pressure supports a column of mercury about 760 mm high. 760 mm Hg = 1 atm= 101 kPa
Pressure Conversion If the barometer reads 753.3 mm Hg, what is the atmospheric pressure in atm and kPa? 1 atm 753.3 mm Hg = 0.9912 atm 760 mm Hg 101.325 kPa 753.3 mm Hg = 100.4 kPa 760 mm Hg
Sample problems 665 mm Hg 0.9803 atm 96.8 kPa 0.9706 atm 98.65 kPa 744.4 mm Hg Pressure Conversions: 1. 0.875 atm to mmHg 2. 745.0 mmHg to atm 3. 0.955 atm to kPa 4. 98.35 kPa to atm 5. 740.0 mmHg to kPa 6. 99.25 kPa to mmHg Temperature Conversions: 1. 250 Kelvin to Celsius 2. 339 Kelvin to Celsius 3. 17 Celsius to Kelvin 4. 55 Celsius to Kelvin 5. -200 Celsius to Kelvin
pressure volume Graph the following information Pressure (KPa)Volume (L) 100 5.00 110 4.55 120 4.16 130 3.85 140 3.57 K (VP) 500 500.5 499.2 500.5 499.8 Is there a relationship between pressure and volume? P1V1 = K = P2V2
Boyle’s Law For a given mass of gas at constant temperature, the volume of a gas varies inversely with pressure. P1V1 = P2V2
volume temperature Graph the following data Temperature (K)Volume (L) 298 5.00 323 5.42 348 5.84 373 6.26 398 6.68 K (V/T) 0.0167 0.0168 0.0168 0.0168 0.0168 Is there a relationship between pressure and volume? V1/T1 = K = V2/T2
Charles’ Law Charles discovered that volume is directly proportional to its Kelvin temperature if a fixed mass remains under constant pressure. V1 V2 T1 T2 =
►Practice, p.154#11 - 13 ►Practice, p.156#14 - 18
Combined Gas Law V1P1= V2P2 T1 T2
►Practice, p.159#20 – 23,25-26 ►Section 4.1 Questions#1 – 7, 9a, 10 - 12