Chapter 5 Gases

Chapter 5 Gases

WHY?

Sketch of ModernBalloons

WHY?

Mathematics

V/T = constant

1.00PSI

8.00PSI

8.00

WHY?

PSI

Mathematics

PV = constant

Mathematics

V/n = constant(n = moles)

Moles

273K ATM

1.00

804K ATM

9.79

(atm)

Mathematics

P/T= constant

MathematicsSummary

V/n = constant

V/T = constant

P/T = constant

PV = constant

MathematicsSummary

V/nT = constant

P/T = constant

PV/nT = constant

MathematicsSummary

PV/nT = constant

PV = nTconstantconstant = R

PV = nRT Ideal Gas Law

Conditions of UsePV = nRT Ideal Gas Law

P units must be atm’s

V units must be liters

T must be in Kelvin

Gas Law ResourcesPressures equivalent to the standard 1.00 ATM

28.3 ft. H2O

29.92 in. Hg

76.0 cm Hg

760.0 mm Hg

760.0 torr

14.7 psi.

1.013 bar

1.013 x 105 Pa

101.3 kPa

(1 Pa = 1 Nt/M2)

PracticeFill out the following chart.

mm Hg. atm. kPa. bar

1215 .

0.714 .

143 .

0.904 .

Gas Law ResourcesTemperature - must be absolute - never negative

Temperature must be in Kelvin

K = oC + 273

PracticeCalculate the volume of 1.0 mole of a gas at Standard Temperature and Pressure.

PracticeFill out the following chart for C4H10

Press. Vol. Temp. Moles Grams

1.75 L 19 oC 1.66 .

0.895 atm 6.0 oC 14.0 .

433 mm Hg 92.4 mL 0.395 .

1.74 bar 8.66 L 310 K .

Experiment

Experiment

Experiment

4 Fe + 3 O2 → 2 Fe2O3

Fe + N2 → NR

Interpretation

•Air contains both N2 and O2

•Each gas has its own independent pressure.

•“The sum of all individual gas pressures in a gas mixture is equal to the total pressure” DALTON

•Dalton’s Law of Partial Pressures

(go to video)

KMT•Kinetic Molecular Theory of gases

Gases consist of very tiny particles in continuous random motion.

Particle collisions are elastic(no energy lost).

Particle volume is negligible.

Particle interaction is negligible.

molecular speed causes both pressure and volume of gases

Graham’s Law Often called Grahams’ Law of Diffusion - in error Diffusion - movement of gas down an open tube complex and influenced by many factors.Effusion - movement of gas through small holes.Graham’s Law of Effusion of Gases“At a given temperature and pressure, gaseous effusion rate in moles per time unit, is inversely proportional to the square root of the molar mass of the gases”.

effusion rate of B = √effusion rate of A √

Ideal vs Real Review KMT. Obvious non-realities.

Some gas molecules are NOT tiny.

Many gas collisions DO lose energy

Gas molecules HAVE a noticeable volume

Some molecules have SIGNIFICANT interaction.