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GASES. Identify the abundances of the naturally occurring gases in the atmosphere. Describe the historical development of the measurement of pressure. Describe the various units used to measure pressure. Earth’s air is composed of two types of gases: Permanent Variable

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## GASES

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**Identify the abundances of the naturally occurring gases in**the atmosphere. • Describe the historical development of the measurement of pressure. • Describe the various units used to measure pressure.**Earth’s air is composed of two types of gases:**Permanent Variable Nitrogen 78.1% Water vapor 0 - 4%Oxygen 20.9% Carbon Dioxide 0.035% Argon 0.9% Methane 0.0002%Neon 0.002% Ozone 0.000004%Helium 0.0005%Krypton 0.0001%Hydrogen 0.00005%**Torricelli (1608-1647) developed the first**• Barometer - measures air pressure • Height of mercury supported by atmospheric pressure at sea level is 760 mm.**Pascal (1623-1662) added to Torricelli’s “barometer.”**• Height affects the pressure of the atmosphere. Gay-Lussac(1778-1850) observed the law of combining volumes in chemical reactions. • Two volumes of hydrogen combined with one volume of oxygen to form two volumes of water. 2 H2 + O2 2 H2O**Gas/Vapour Pressure:**Pgas = Patm + h (greater than air) Pgas = Patm – h (less than air)**Dimensional Analysis**Problem-solving method using relationships to change units without changing value. Relationships are made by relating two things by their equivalent "amounts" as a ratio. • 1 filling OR 2 cookies • 2 cookies 1 filling**Dimensional Analysis (Converting Units):**Determine the unit ratio needed. Multiply the base unit by the unit ratio. (make sure you have the new unit on top) • 20 fillings = ? cookies • 1 fillings OR 2 cookies • 2 cookies 1 filling • 20 fillings x2 cookies = 40 cookies • 1 fillings**2. 3 m = ? cm**• 1 m or100 cm • 100 cm 1 m • 3 m x100 cm = 300 cm • 1 m**3. 5 kL = ? mL**• *need to multiply by TWO factors: • kL L mL • 1 kLand 1 L • 1000 L 1000 mL • 5 kLx1000 L x 1000 mL = 5 000 000 mL • 1 kL 1 L**1. atmosphere (atm):**• 1 atm = 760 mmHg = 101.325 kPa • 2. Pascal (Pa) – standard international (SI) units. • Defined as 1 Newton of force per m2. • Use kiloPascals. • 3. Millimetres of mercury (mmHg) – not common. • 4. Pounds per square inch (psi) - Imperial • 1 kPa is equal to 0.145 psi 1 atm is equal to 14.7 psi.**What is the pressure of the gas in kPa?**Pgas = 762 mm + 15 mm = 777 mmHg • 777 mmHg x101.3 kPa = 103.6 kPa • 760 mmHg**Gas pressure is due to the force of gaseous particles**colliding with their container. • Torricelli invented the barometer to measure atmospheric pressure. • Units used: mmHg, atm, kPa, psi • Using a manometer: • gas pressure > air pressure Pgas = Patm + h • gas pressure < air pressure Pgas = Patm – h.

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