Atmospheric Pressure:

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

• Measured using a barometer (invented by Torricelli); standard atmospheric pressure is 760 mm Hg.

• Factors affecting barometric pressure include altitude and weather conditions.

Units of Pressure:

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

• Conversion: 1 atm=760 mm Hg=760 torr=101325 Pa

Gas Laws:

• Boyle's Law: At constant temperature, pressure and volume are inversely proportional. P1V1=P2V2

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

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

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

• Ideal Gas Law: Relates pressure, volume, temperature, and moles of a gas. PV=nRT

  • R (gas constant) = 0.0821 L·atm/(mol·K)

Solving Gas Law Problems:

• Always use Kelvin for temperature: T(K)=T(^C)+273

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

• Identify which law applies based on which variables are held constant.

• For combined or ideal gas law problems, set up the equation with known and unknown variables, solve algebraically, and substitute values.

Conceptual Understanding:

• Gas pressure results from collisions of gas molecules with surfaces.

• Volume, pressure, temperature, and amount of gas are interrelated; changing one affects the others according to the gas laws.

• Real gases deviate from ideal behavior at high pressures and low temperatures.