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 such as altitude and weather can affect barometric 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=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 gas. PV=nRT where R = 0.0821 L·atm/(mol·K).

Solving Gas Law Problems:

• Identify which variables are constant and which are changing.

• Convert all temperatures to Kelvin (K = °C + 273).

• Use appropriate gas law equations to solve for unknowns.

• Pay attention to units and use conversion factors as needed.

Sample Calculations:

• To find the new volume, pressure, or temperature, rearrange the relevant gas law equation and substitute known values.

• For the Ideal Gas Law, solve for the unknown variable (e.g., moles, volume, pressure) using PV=nRT.

Conceptual Understanding:

• Gas behavior is predictable under typical conditions using the gas laws.

• Changes in pressure, volume, temperature, or amount of gas affect the other variables in a systematic way.