RWF CHAPTERS 13/14 NOTES Gases

Here’s one thing we know about gases: 1 mol of any gas at STP has V= 22.4L

Avogadro’s Law Equal volumes of gases at same P and T contain equal number of particles V= kn n = # of moles.

Observations about gases -Gases have mass -Gases can be compressed -Gases fill their containers, shape and volume does not stay constant -Diffusion -Gases exert pressure. -Pressure depends upon temp Gases have low density

All observations can be explained by the Kinetic Theory of Matter = Matter is made of tiny particles that are in constant motion

Pressure Pressure is the force per unit area on a surface Pressure varies with altitude and temperature Pressure is caused by air molecules crashing against a surface To a lesser extent pressure is caused by the weight of the air above you {Temperature is the average kinetic energy of the particles of a substance}

ASSUMPTIONS that we make when we study gases --Elastic Collisions = particles hit other particles and walls of container and eyeballs without slowing down --Distance between particles is large --There is no interactions between molecules --Particles are “point masses”, that is, the particles have zero or negligible volume.

-According to the kinetic theory of matter, when a Gas temp rises here’s what happens: as particles move faster, there are more collisions per second and collisions have more energy, therefore pressure rises

Measuring Gases Amount of gas particles (moles) Volumes (l or ml) Temp (oC or K) Pressure 1.00 atm = 101.325 kPa = 760. mmHg = 760. torr = 14.70 lbs/in2

Torricelli’s Barometer

8.3 lbs/in2

8.3 lbs/in2 14.70lb/in2

8.3 lbs/in2 760 mmHg 14.70lb/in2

Manometer=a device used to measure pressure of container of gas See pg. 389

STP = Standard Temperature and Pressure is 273K and 1 atm.

Boyle’s Law As volume decreases, pressure increases (think of squeezing a balloon) PV=k (k is a constant) P1V1=P2V2 At constant T

Charles Law As temp rises, volume rises constant P V/T= k at constant P V1/T1 = V2/T2

Put them all together: P1V1/T1 = P2V2/T2

Dalton’s Laws of Partial Pressures- The sum of the partial pressures of all the components in a gas mixture is equal to the total pressure of the gas mixture. Pair = PN2 + Po2 + Pco2 + PH2O +…..

Ideal Gas Law PV= nRT P = Pressure n = moles V = Volume (L) T= Temp (K) R = 0.0821 atm-L/mol-K = 8.314 K Pa-L/mol-K

Gas Law Constants (R): 0.08206 atm-L/mol-K 1.987 cal/mol-K 8.314 J/mol-K 8.314 Pa-m3/mol-K 62.36 torr-L/mol-K 8.314 kPa-L/mol-K

How many moles of a gas at 100oC does it take to fill a 1 How many moles of a gas at 100oC does it take to fill a 1.00L flask to 1.50 atm ?

PV= nRT (1.50Atm)(1.00L) = n(.0821atm-L/mol-K)(373K)