Atmospheric Pressure:

• Atmospheric pressure is the force exerted by gas molecules in the air as they strike surfaces.

• Measured using a barometer; standard atmospheric pressure at sea level is 760 mm Hg.

• Factors such as altitude and weather can affect atmospheric pressure.

Units of Pressure:

• Common units: atmospheres (atm), millimeters of mercury (mm Hg), torr, pascals (Pa), and pounds per square inch (psi).

• Conversion factors:

  • 1 atm = 760 mm Hg = 760 torr = 101,325 Pa = 14.7 psi

Gas Laws:

• Boyle's Law: At constant temperature, pressure and volume are inversely proportional. PV=k or P1V1P2V2=k

• Charles' Law: At constant pressure, volume and temperature (in Kelvin) are directly proportional. VT=k or V1T1=V2T2

• Avogadro's Law: At constant temperature and pressure, volume and moles of gas are directly proportional. Vn=k or V1n1=V2n2

• Combined Gas Law: Relates pressure, volume, and temperature for a fixed amount of gas. PVT=k or P1V1T1=P2V2T2

• Ideal Gas Law: Relates pressure, volume, temperature, and moles of a gas. PV=nRT where R is the universal gas constant (0.0821 L·atm/K·mol).

Problem-Solving Tips:

• Always use Kelvin for temperature in gas law calculations: T(K)=T(^b0C)+273

• Convert all units to match the gas constant R when using the ideal gas law.

• For combined gas law and other gas law problems, identify which variables are held constant and which are changing.

• Use appropriate conversion factors for pressure units as needed.

Conceptual Understanding:

• Gas laws describe the relationships between pressure, volume, temperature, and amount of gas.

• Understanding these relationships helps predict how gases will behave under different conditions.

• Real gases may deviate from ideal behavior under high pressure or low temperature.