The Gas LawsChapter 14

Chemistry

Remember gases behave differently

Gases are affected byTemperature

Pressure

Volume

Boyle’s LawRobert BoyleRelationship between pressure and volumeP1V1 = P2V2

Inverse relationship – As volume decreases, pressure increases

Example ProblemA sample of helium gas in a balloon is compressed from 4.0 L to 2.5 L at a constant temperature. If the pressure of the gas in the 4.0 L volume is 210 kPa, what will the pressure be at 2.5 L?

P1V1 = P2V2

Boyle’s Law Activity

Marshmallow in Syringe

Dalton’s Law of Partial Pressures

Charles’s LawJacques Charles

Relationship between temperature and pressure

Direct Relationship

V1 = V2 T1 T2

Sample ProblemA gas sample at 40.0oC occupies a volume of

2.32 L. If the temperature is raised to 75oC, what will the volume be, assuming the pressure remains constant?

Charles’s Law ActivityCold Balloon

Bottle Crush

Popcorn

Gay-Lussac’s LawRelationship between temperature and

pressure

Volume must be held constant

Direct relationship

P1 = P2 T1 T2

Sample ProblemThe pressure of a gas in a tank is 3.2 atm at

22.o oC. If the temperature rises to 60 oC, what will be the gas pressure in the tank?

Combined Gas Law

P1V1 = P2V2 T1 T2

Sample ProblemA gas at 110 kPa and 30.o oC fills a flexible

container with an initial volume of 2.oL . If the temperature is raised to 80oC and the pressure increased to 440 kPa, what is the new volume?

Avagadro’s PrincipleEqual volumes of gases at the same

temperature and pressure contain equal numbers of particles

Molar volume = the volume one mole of gas occupies at 0oC and 1.0 atm pressure

One mole of any gas will occupy 22.4L

Practice ProblemCalculate the volume that 2.0 Kg of methane

gas (CH4) will occupy at STP

Ideal Gas LawIdeal gases have almost no volume and the

particles are far enough apart to not exert any type of repulsive or attractive force on another particle.

Do not exist in real world, but most gases behave like ideal gases at STP

PV=nRT

PracticeCalculate the number of moles of gas

contained in a 3.0L vessel at 3.00 x 102 K with a pressure of 1.5 atm

PV = nRTP = 1.5 atmV = 3.0LR = .0821T = 3oo KN = ?

Gas Stoichiometry

Remember, coefficients represent the number of moles of a reactant or product

2 C4H10 + 13 O2 8 CO2 + 10 H2O

Calculations involving only volume

CH4 + 2 O2 CO2 + 2H2O

It takes 2 liters of oxygen to react with 1 L of methane to produce 1 liter of carbon dioxide and 2 liters of water

Volume to volume problemWhat volume of oxygen gas is needed for the

complete combustion of 4.0 L of propane gas (C3H8)? Assume constant pressure and temperature.

C3H8 + 5O2 3CO2 + 4H2O

1. Start with what you know: 4.0L C3H8

2. What is the ratio of Oxygen to propane? 5 oxygen 1 propane

3. Multiply the amount of propane by the ratio to get oxygen 5 x 4 = 20 L

Volume to Mass ProblemAmmonia is synthesized from hydrogen and

nitrogen gases. N2 + 3H2 2 NH3

If 5.00 L of nitrogen reacts completely by this reaction at a constant pressure and temperature of 3.00atm and 298K, how many grams of ammonia are produced?

1. Analyze problem (V, P, T, )

2. Solve for unknownDetermine volume ratioUse ratio to determine liters of ammonia

producedRearrange and use ideal gas law to solve for n

(use liters of ammonia produced as V)3. Convert moles of ammonia to grams of

ammonia