Gases KMT = particles constant motion AKE, temperature, pressure, volume, amount of a gas are all...

Gases• KMT = particles

constant motion• AKE, temperature,

pressure, volume, amount of a gas are all related

Pressure & Force• D/t collisions of

molecules on surfaces

• P = defined as the force per unit area on a surface = force/area

• Force unit = newton (N)

The Barometer

• Pressure depends on area of contact; smaller area, greater pressure

Ex.: high heels; ballerina• Atmosphere exerts

pressure - total of individual gas pressures (mostly N, then O)

• Measured using barometers

• Units(ie. 1 torr = 1 mm Hg)

Dalton’s Law of Partial Pressures

• Partial pressures are exerted by individual gases

• Law states that total pressure of a gas mixture is the sum of the component pressures

• PT = P1+P2+P3…

Boyle’s Law• Inversely relates

pressure and volume

• Examples?• P1V1=P2V2

• What is the constant?

MUST KNOW

• Use the temperature in Kelvins when solving these gas problems.

• K = ºC + 273• STP means standard temperature (0ºC)

pressure (1 atm).• 1 atm = 101.3 kPa = 760 torr = 760 mm Hg

Charles’s Law• Directly relates

volume and temperature

• V1/T1 = V2/T2

• What is the constant?

• K = degrees C + 273

Gay-Lussac’s Law• Directly relates

pressure and temperature

• P1/T1=P2/T2

• Constant?

Combined Gas Law

Avogadro’s Law• Equal volumes of gases

at the same temperature and pressure contain equal numbers of molecules.

• Example: At the same temperature and pressure, balloons of equal volume have equal numbers of molecules, regardless of which gas they contain.

Molar Volume of a Gas

• 22.4 L at STP• STP = 1 atm and

0 degrees C (273 K)

Ideal Gas Law• Solve for moles within a gas PV = nRT

R is a constant (0.0821 Lxatm/molxK). This is used when the volume is in liters, the pressure is in atmospheres, and the temperature is in Kelvins.

n is the number of moles

Use a table for values of R when other units for n, P, V, and T are used.

Comparison of Diffusion with Effusion

• Effusion is the process by which gas molecules under pressure pass through a tiny opening.

• Diffusion is the mixing of two gases by random molecular motion.

Graham’s Law of Effusion• Rates of effusion of

gases at the same temperature and pressure is inversely proportional to the square roots of their molar masses

• Square root of Molar Mass B/Square root of Molar Mass A